Circle Track Crate Engine Technical Manual
Contents
1. Sealing Bolts The Circle Track Crate engines are sealed from the factory with 8 bolts in key locations The locations are such that tampering with the engine is unlikely without destroying or damaging the bolt head Each bolt has the familiar GM logo laser etched on the head as a quick identifier Note the GM logo is trademarked and there are penalties for copying the trademark In 2005 GM started using a clear zinc coating on the bolts and added an additional anti counterfeiting process called Info Glyph This process allows information to be encoded into a square of dots laser etched on the bolt The 8 bolt locations are 2 bolts in the intake manifold 2 bolts in the front cover 2 bolts in the oil pan amp one bolt in each cylinder head The valve covers are not sealed as it is important to properly lash the valves See valve lash procedure on page 9 The bolts are designed so that during installation the head breaks off at the proper torque Example On the sealed cylinder head bolt the hex head portion of the bolt breaks away at 65 ft Ibs Each bolt is designed specifically for that location and torque The head is rounded off so it difficult to remove without damaging the head and sending up a red flag that the engine has been tampered with Replacement bolts are not sold to the public This ensures the integrity of the program See the Rebuild section to understand repairs rebuilds and replacement bolts2. PERFORMANCE PARTS a a a a s Circle Track Crate Engine Technical Manual 889538604 88958602 19258602 88958603 p n 88958668 Contents Introduction amp Legal Information History Where to Buy Warranty Sealing Bolt Description Circle Track Engine Packages 88958602 19258602 350 HP Engine Assembly 88958603 355 HP Engine Assembly 88958604 400 HP Engine Assembly Installation Information Valve Lash Instructions Break In Procedure Tune Up Specifications Engine Components Blocks amp Pistons Cylinder Heads Intakes amp Front Covers Rocker Arms amp Oil Pans Engine Specifications Engine Specifications Chart Valve Seat Machining Valve Springs Camshaft Specifications Torque Specifications amp Sealers Pg 3 Pg 4 Pg 5 Pg 6 7 Pg 8 12 Pg 13 16 Pg 17 23 Pg 24 26 Page 1 Contents Continued Flywheel amp Transmission Components Pg 27 28 Technical Inspection Procedures Pg 29 35 Additional Sealing Methods P amp G Compression Ratio Checking Whistler Combustion Chamber Volume Valve Spring Rate Rocker Arm Ratio Checking Engine Parts Number Lists Pg 36 39 Listing of Original Part Numbers List of Rebuild Part Numbers Complete List of Bolt Part Numbers List of Updates from Previous Manual Pg 40 This Technical Manual is dedicated to the memory of Robert E Bob Cross 1957 2010 Copyright July 2006 General Motors Corporation Revised May 2010 Page 2 Introduct
3. The bottom photos show the difference between the 2 sides of the fixture using a 1 5 roller rocker arm The left photo shows proper fit for the GM 1 5 roller rocker arm on the fixture The pushrod seats into the rocker arm cup properly The right photo shows the same 1 5 roller rocker arm sitting on the 1 6 side of the fixture as you can see the pushrod does not fit the rocker arm cup properly The reverse would be true for a 1 6 rocker arm The pushrod cup will not fit properly on the 1 5 side Correct Pushrod Fit 1 5 ratio Rocker Incorrect Pushrod Fit for 1 5 Rocker Please note There is only a 050 difference between the center stud and the pushrod cup center on a 1 5 and 1 6 rocker arm The 1 6 rocker arm distance being shorter Page 35 Engine Parts List Engine Block Components on 88958602 19258602 88958603 88958604 12561723 N Not Serviced 12561723 12561723 10105123 Not Serviced Not Serviced 14088556 14088556 9441003 9441003 2 12554553 2 12554553 2 12554553 2 14101058 2 14101058 9439915 9439915 2 14088561 2 14088561 14088561 14088561 Rear Cam Plug 10241154 10241154 __ Dowel Pin Bellhousing ________ 2 12838119 2 12938119 2 12398119 2 12338719 12556307 10108688 Piston St tant 88894280 10759436 10159436 88960604 Cylinder Head Components 12558060 12558060 12556463 12464298 Cylinder Head Bare 12529093 12529093 NS NS Intake Valve f 10241743 1
4. This photo shows the GM Logo and Info Glyph dot matrix Page 5 GM Circle Track Engines This section is a brief overview of the 3 engine packages that are available from GM The following pages outline the highlights of each engine including torque and horsepower figures The final page has a chart that covers the technical specifications of each engine P N 88958602 and 19258602 602 88958602 and 19258602 are rated at 350 hp 5000 rpm The 602 makes 390 ft lbs torque 3800 rpm It fits well in lower level introductory classes that are looking for affordable horsepower such as factory stock modified and truck It comes complete intake to pan and includes an HEI distributor It does not include a flywheel or water pump The engine uses a 4 bolt block cast iron crank powder metal rods and cast pistons The 9 1 1 compression ratio with iron Vortec heads offer a good balance of power and durability The 8 1 2 deep oil pan holds 8 quarts including the filter The engine has a dual plane high rise aluminum intake This engine weighs 434 Ibs as delivered P N 88959603 603 88958603 is rated at 355 hp 5250 rpm It makes 405 ft lbs torque 3500 rpm It fits well in mid level classes such as limited late model and late models The engine comes complete intake to pan and includes water pump HEI distributor and a flywheel The 4 bolt block steel crank powder metal rods and high silicon pistons make a great fo
5. then 50 ft Ibs and 65 ft Ibs final pass Use 12346004 Teflon sealer on all bolts unless new Intake Torque Sequence for 88958602 19258602 amp 88958604 Engines The torque sequence to the left is for intakes used on 8602 amp 8604 engines Torque to 11 ft Ibs all bolts Use 12346004 Teflon sealer on bolts unless new Let intake set a short period and re torque Intake Torque Sequence for 88958603 The torque sequence to the left is for intake manifolds used on 8603 engines Torque to 35 ft Ibs torque to 15 ft lbs first pass then 35 ft lbs final pass Use 12346004 Teflon sealer on all bolts unless new Page 26 Flywheel amp Transmission Components This section is intended to identify the flywheel components that GM recommends The aftermarket has designed small clutch packs that fit smaller bell housings used in some applications This section will also will help clarify the confusion between 1 pc amp 2pc rear seals and flywheel balance All three circle track crate engines use Ipc rear seals It s a much better seal and was introduced in production engines in 1986 When using a 1pc rear seal the flywheel must have a counterbalance All three engines are internal external balanced It s not like the old 400 engines They had both a counterbalanced flywheel and balancer You cannot use a 400 flywheel on circle track engines The balance is in a different location and the bolt pattern is different Y
6. Rod Weight 595 grams 595 grams 595 grams _ _ 3 46 E E NO E grinding of crank during rebuild 005 to Square Surface During 1st rebuild Maximum Minimum Crank Stroke Throughout the book we have tried to define minimal allowable modifications recommended This common theme is intended to be strong The industry is where it s at today because of lax rules enforcement increased costs of components and the pressure to win The competitors are shelling out lots of money to purchase parts that may not be necessary for close competition In some cases those parts hurt performance The short track industry needs to keep costs under control Rebuilding of engines seems like the least expensive way to go In some cases that maybe true depending on the class and allowable rules but in most cases it allows purchase of parts that are expensive and that drives up the cost of the engines It is imperative that tracks do not relax the rules Increased inspections and checks must be part of the program Crate engines were born out of a need to make racing affordable again It s in the hands of the tracks to contain the modifications to engines If the track allows any of these specifications to be relaxed then costs will begin to increase Keep tight checks on your approved re builder It might be a good idea to stop in and check on your approved re builder from time to time when an engine is in his shop GM engines are designe
7. engine is 5800 rpm Page 8 Valve Lash Procedure This page covers the proper procedure to lash the valves It is imperative to set the valve lifter lash properly on each of the engines All three engines use the same procedure It is also critical that the rocker arm nuts are properly secured so they do not loosen during operation The 602 amp 603 engines use Kool Nuts and the 604 uses aluminum roller rockers Each has a locking nut with set screw The set screw is the only way to Keep valve lash secured Refer to Tune up section for photo of cool nut and set screw Recommended Lash is Zero to 4 turn Hot To properly set the valve lash warm up the engine to normal operating temperature 180 190 degrees F water temp and follow the procedure below Remove the valve covers and disconnect power to distributor Important When lashing valves it is best to loosen the rocker arm nut slightly while rotating the pushrod with your other hand between two fingers until the pushrod rotates easily Then set the valve lash by tightening the rocker arm nut while rotating the push rod between your fingers until you feel it stop rotating When it stops rotating you are at zero lash Next tighten the set screw in the rocker arm nut against the rocker arm stud Then rotate the rocker arm nut and the set screw at the same time 4 turn maximum This will allow the set screw to lock properly and hold the valve lash at 4 turn Use the sequence bel
8. 0241743 10241743 _ 12555331 12550909 12550909 12551313 Valve Spring f 1012n 10241744 10212808 24503856 24503856 N A 10212809 N S 10089648 19210724 Kool Nut Kit 88961233 88961233 N A A ae i Am Push Rod 14095256 14095256 10241740 10241740 Dowel Pin Cylinder Head 4 585927 4 585927 4 585927 4 585927 12366573 12496822 93440806 N 10096197 10096197 Page 36 Engine Parts Lists Continued Camshaft Components CamshaftGear 340235 12552129 12552129 Timing Tab 8 Balancer 3991436 3991436 3991436 Timing Tab _6 3 4 Balancer 3991435 3991435 3991435 __ OiPan NANA TNA Oil Pump 98442037 14044872 14044872 Oil Pan amp Screen 25534353 _ 25534354 _ 25534354 Reinforcement Oil Pan LH 12553058 12553058 12553058 Reinforcement Oil Pan RH 12553059 12553059 12553059 Adapter Oil Fitter 3952301 3952301 3952301 Engine Dressitems gt Valve Cover Kit 25534359 25534359 25534359 Valve Cover Breather Kit 25534355 25534355 25534355 __ Miscellaneous Parts Thermostat 180degree 12555290 12555290 12555290 __ Spark Plug Wires 90 degree boot 12361051 12361051 12361051 Spark Plug MR43LTS 5614210 5614210 5614210 Page 37 Engine Parts Lists Continue Factory Rebuild Components In Kit Form Main Bearings 1 4 001 U S 12531215 12531215 12531215 12531215 Rod Bearings Std 16 req 12523924 12561341 12523924 12523924 Ring Package Se
9. 03 88958604 Flywheel 14 168tooth lightweight 14088646 14088646 14088646 Note 14088646 weighs approximately 15 Ibs Zo Starter Bots 5 tbs 5nis 5nibs The photo to the left shows a p n 14061685 crankshaft bushing Install this roller bearing bushing in the rear of the crankshaft to minimize friction losses Page 28 Tech Inspection Procedures This section covers technical procedures To keep competition equal tracks must put proper procedures in place to police their engines If track owners or promoters do not Keep a close watch on engine modifications then competitors will exploit every opportunity to make modifications and the savings from the crate engine program will be lost Every track must take seriously the integrity of the program and be willing to implement strong penalties for those caught tampering with bolts or modifying engines Study these procedures closely Take time to practice the tests on a known engine Make sure you are familiar with the test and the equipment before testing in the field Any signs of inexperience or lack of confidence may cause the tech inspector and track to lose credibility As you review the tests you will find one common theme Engine Temperature it is the most critical item with most of the tests One mistake here and your numbers will be off Sealing Bolts Sealing bolts are the area of most concern for everyone Every engine GM sells is fully sealed from the factory
10. 1 93 Octane Unleaded fuel is recommended No need to run leaded fuel or 101 104 octane Leaded fuel contaminates the oil and can foul the spark plugs All three engines have compression ratios of 10 1 or less so the higher octane is of little value The valve seats are designed to run on unleaded fuel plus unleaded fuel cost less and saves money each night Some of the tracks amp sanctioning bodies add traces of lead for Off Road Use which should not affect performance Headers In GM testing the engines were tested with stepped headers The headers were 1 5 8 primary tubes 10 long and then stepped to a 1 3 4 tube The total length was 33 with a 3 1 2 collector All three engines have efficient combustion chambers and exhaust ports Therefore it s normal to see flames out the back of the car during deceleration The more efficient the headers the worse the flames will be Most 2bbl classes need headers that are designed to scavenge the exhaust to make power and this pulls more fuel through the engine That is not necessary when using the recommended 4 bbl carburetor on GM engines Recommended Oil GM recommended Mobil 1 synthetic oil for all three engines Extensive testing has proved that synthetic oil provides better lubrication qualities under extreme conditions and lasts longer Page 12 Engine Components A lot of engineering amp extensive testing goes into each component in the GM circle track engines The parts
11. 603 88958604 esftibs e5fibs e5ftibs 006 bolt stretch preferred 20 ft Ibs additional 55 degree 45 ft Ibs if no angle gauge is available 27 N m additional 55 degrees 61 N m if no angle gauge is available isftibs _ isitibs f5fibs e6 ftibs _eoftibs _ edftlbs B5ftlbs asftlbs 5nis mnis mabs mns 18ftibs i8 tibs ietis _ _ ists ieftibs e5 ftibs __ esftibs esftlbs eO ttibs eonibs fifths Mrs iiftlbs _ _25ftibs 25ftibs 25ftibs feftibs iens ienis oirn OOO S Nut or Bolt Corner oi pan _ i5 fibs _ leftlbs __ tsftlbs Oii Baffel Nut 100inch Ibs 100 inch Ibs 100 inch Ibs Oii Drain Pug 5nis snis fi5fnibs Starter Bots 5fibs 5nibs 35fibs Spark Pug SCS RIS Sns 5fibs Valve Cover Bolts 100inch Ibs 100 inch Ibs 100 inch Tbs Water Pump Bolts bonibs sonibs sonis Fuel Pump Cover Bolts 100 inch Ibs 100 inch Ibs 100 inch Tbs Fuel Pump Bots 5 Ribs snis 5fnibs Page 25 Torque Specifications amp Sealers continued Sealing bolt installation Torque heads intakes front cover and oil pan with stock bolts in all locations prior to installing sealing bolts After final torque is done remove stock bolt and install sealing bolt and tighten until head breaks off Do not install sealing bolt first Cylinder Head Torque Sequence The diagram to the left shows the proper torque sequence for all three engines Torque bolts to 65 ft lbs Torque 40 ft Ibs
12. Balancer Page 39 Notes Catalog Changes 10 19 09 changes to page 45 part numbers Main and rod bearings 3 1 10 changes 1 Page 18 corrected crank forging number on 603 amp 604 engines from 10243880 to 14088532 2 Page 43 Changed crankshaft service number from 12566307 to 12556307 typo 4 27 10 changes Added engine 19258602 throughout manual Page 18 Corrected 8603 Chamber Volume Add 19258602 story to last page Add crankshaft bob weights to last page Page 13 Picture of piston added and description modified Page 16 Picture of kool nut added and description modified Pages 36 39 update all part numbers to current 10 Remove references to fuel testing noise testing and carburetor tech procedures 11 Updated table of contents pages Soe ee eS Page 40 Crankshaft Weight grams Erain Crankshaft gine Parn Number 602 Engines Crank and Piston Changes General Motors has taken great pride in the crate engine program since its inception in 2002 by being able to provide proven reliable and affordable engine packages to grass roots racers The main goal always has been to produce a line of engines that were all built with the exact same parts to keep a level playing field for all competitors Over the years the parts content of these engines have remained the same with no significant changes in content However in the summer of 2009 the piston supplier for the 8602 engine approached General Motors and explaine
13. Each engine is built to the same standards and specifications After it leaves the factory it is up to the tracks to police them GM is not responsible for engines that have been tampered repaired or rebuilt GM Factory Sealing Bolt Inspection Procedures Inspection of the sealing bolts is simple All 8 bolts in each engine have the GM logo laser etched on the head of the bolt In May of 2005 GM started installing bolts with a zinc coating on them This makes the GM logo easier to read and reduces rusting of the bolt The photo on the left shows 1 The GM logo to the left of the square of dots 2 The square of dots which is the Info Glyph encrypted message Info Glyph encrypting is described next The photo on the right shows a head bolt installed on an engine Page 29 Additional Sealing amp Tracking Methods There are several other ways to seal and track engines Some are simple and some are more complex By adding another level of seals this reduces chances the engine is modified Tracking engines by serial numbers is the best way to understand who has what engine and when it is serviced The local track can issue serial numbers and stamp them on the block and heads That engine will be required to be registered on the track web site This will allow the track to determine how long an engine is in service and who owns it A registration fee maybe required to cover overhead costs SSS m Drilled bolt seals You can in
14. LVE LIFT N VAL ve LIFT 100 0 SIs li OVERLAP AREA 13 0 INP ag 24502476 camshaft specifications Page 22 Engine Specifications Continued 88958603 amp 604 Engine Camshaft Specifications P N 10185071 camshaft is installed in both the 603 amp 604 engines It is a roller camshaft design and uses hydraulic roller lifters This camshaft has a red dab of paint located near the camshaft gear for identification See section on valve lash for proper lash and procedure Valve Lift 474 intake and 510 exhaust Duration 050 208 degrees intake and 221 degrees exhaust Cam lobe centerline is 112 degrees Intake lobe lift 316 Exhaust lobe lift 340 Intake base circle radius 60684 Exhaust base circle radius 583 Dowel pin hole Retarded 5 degrees from centerline of 1 cylinder exhaust lobe advanced 107 degrees from centerline of 1 cylinder intake lobe 107 5 112 degrees lobe separation Note 010 all dimensions and 5 degrees angularity Shown below is a graph of the cam profile for cam p n 10185071 as used in 88958603 and 88958604 engines 180 REF 186 REF Th im 116 108 51600 YALYE LIFT 96 47424 VALVE LIFT 44 94 4B OVERLAP AREA 11 43 IN s 10185071 camshaft specifications 322 320 Page 23 Torque Specifications amp Sealers All of the torque specifications are in one location to be used as a Quick Guide during rebuilds Also i
15. ack applications The potential for cost savings was tremendous Based on the success of those racers GM Racing and GM Performance Parts engineers spent time in 2001 developing several circle track engine packages based on their proven small block Chevy crate engines That development led to 3 engines released in 2002 88958602 88958603 and 88958604 Commonly known as the 602 603 amp 604 the last 3 digits of the part number these three engines fit easily into most existing racing classes with minor adjustments to the rules typically weight breaks Each engine is assembled with all new parts on a production line to keep costs down The engines then are up fitted with special oil pans valve covers and sealing bolts Factory sealing of the engines are one of the keys to the success of the program as this makes it difficult to tamper with the engine and helps maintain equality among the competitors If used as directed the engines should provide several seasons of use with minimal maintenance Where to Buy Circle track crate engines can be purchased from any GM Dealer in the USA Canada and other countries Our recommendation is to contact an authorized GM Performance Parts dealer which is more familiar with GM s high performance parts line Contact 1 800 468 7387 or www gmperformanceparts com to find a dealer near you Warranty Circle track crate engines have no warranty They are sold for off road racing activities Page 4
16. ack testing showed the 650 HP series was the best carburetor choice for all three applications A 750 cfm HP series carb was also tested It didn t make any more horsepower on the dyno and when it was track tested it was too rich and loaded up in the corners Because all three engines make power well before 5500 rpm the larger carburetor can actually hurt performance The Holley HP series is designed with most racing modifications done There are other very good high performance aftermarket carburetors available as well that may be used with proper testing and tuning After installing your carburetor make sure the float levels are set properly the idle mixtures adjusted and idle rpm set Depending on the weather and altitude you may have to change the jet size up or down Do not make large jumps in jet sizes without consulting the carburetor manufacturer or an engine builder Most of the time only a couple of jet sizes is all that is necessary for proper performance Make sure you take care of the carburetor when the season ends Drain the fuel and put the carburetor in a plastic bag or sealed container Do not leave it on the engine the fuel will evaporate and leave a residue in the metering galleries Engine Timing 32 34 degrees of advance should be all that is needed The combustion chambers are very efficient so it doesn t take much timing to make power Don t run more than 34 degrees as detonation can occur Fuel Requirements 9
17. ake amp 1 50 exhaust SS U r p eo i P N 12556463 Photo s show the aluminum cylinder head amp combustion chamber used on the 603 engine Head casting number is 10088113 Valve sizes are 1 94 intake amp 1 50 exhaust ae ek MS Sk Oh se P N 12464298 Photo s show aluminum fast burn cylinder head and combustion chamber used on the 604 engines Head casting number is 12367712 Valve sizes are 2 00 intake amp 1 55 exhaust Push Rods GM uses part number 14044874 HD 075 wall pushrods in the 88958602 engines The pushrod is 7 724 long and 5 16 diameter P N 10241740 is used in 88958603 amp 88958604 engines It is a HD pushrod that has a 060 wall and 7 122 long and 5 16 diameter Page 14 Engine Componen tS Continued Intake Manifolds P N 10185063 intake on the right is used on 603 engines Itis a dual plane medium rise P N 12366573 intake on the left is used on 602 style It uses 12 bolt traditional mounting engines It s a dual plane high rise intake It has the 8 bolt Vortec mounting pattern P N 12496822 intake pictured to the left is used on 604 engines It s single plane high rise intake It has the 8 bolt Vortec mounting pattern Front Covers GM uses two different types of front covers on the 3 engines The photo on the left shows a stamped steel cover that is installed on 602 engines The photo on the right shows the plastic cover that is
18. all that is necessary to seal the intake rails The sealer should be applied slightly up the cylinder head to encase the intake gasket and seal the corner where the intake head and block come together Make sure intake is clean Camshaft Retainer amp Gear Bolts When tightening camshaft bolts we recommend you use Blue Loctite on the threads Oil Pan Bolts amp Oil Pan Gasket No sealer is needed on oil pan bolts They should be installed with light engine oil on threads All three engines use one piece oil pan gaskets No sealer is necessary except in 3 areas 1 Add a slight amount of sealer to the 4 corners of the pan where at the 5 16 bolt holes 2 After pan is installed put silicon sealer around the front of the pan where it meets the timing cover The sealer should encapsulate the gasket between the pan and the timing cover 3 Add sealer at the rear of the pan where it meets the seal adapter This should also encapsulate the gasket between the pan and the aluminum part of the rear seal adapter Front Cover 1 The 602 engine uses a paper style gasket and will require a dab of P N 12346192 silicon sealer at the bottom where the steel cover meets the block and oil pan 2 The 603 amp 604 engines have plastic covers with a built in seal They too require a dab of silicon sealer in the area where block front cover and pan meet Page 24 Torque Specifications amp Sealers continued Torque Specifications 88958
19. alve C L 23degrees 23degrees__ 23 degrees Intake Valve Stem Clearance 0009 001 0009 0027 0009 0027 Exhaust Valve Stem Clearance 001 0012 0009 0027 0009 0027 N A 040 080 050 060 Intake Valve Seat Width o5 cto Exhaust Valve Seat Width 6o ozo o6 65 degrees 1 720 1 745 1 241 1 266 1 305 1 330 _ Note Minimum Valve Seat I D is measured at the center point of steel valve seat where seat is smallest No Modifications are Allowed Below Valve Seat Land in Bowl Area or Any part of the Ports Page 20 Engine Specifications Continued Valve Spring Specifications Below is illustration of a typical valve spring Match up the locations and engine part number with the chart below for the correct specification REFER TO CHART FOR SPECIFICATIONS Valve Spring Specifications New Valve SpringPIN____ azm 12551483 12551403 __ Diameter o r ir Free eign 20r 25 2r Note These specifications are for new valve springs The specification chart shows free height installed height spring o d installed pressure open pressure etc Keep in mind that new spring pressures have some variances The chart notes the two important variances Installed pressure amp open pressure Valve spring pressures will change depending on length of time engine is in service temperature during that perio
20. are tested to production standards and pass hundreds of thousands of miles before being released Quality control standards are maintained during assembly of each engine This section covers some of the differences between the major components in the three engines Engine Blocks All three engines are assembled with brand new 4 bolt main blocks with cast iron caps The main caps are straight bolts They are machined to factory specifications The blocks are designed to use 1 pc rear seal crankshafts Photo to the right shows the 1 pc rear seal adapter which reduces oil leaks It does require a special flywheel that is balanced correctly for these applications p n 14088556 rear seal retainer Pistons The piston on the far left below is installed in 19258602 engines This piston has a grafal coating on the skirt The piston in the center below does not have a skirt coating and is installed in 88958602 engines They both are a cast aluminum dished piston with 4 valve reliefs The piston on the right below is installed in 603 amp 604 engines It s a flat top piston with 4 valve reliefs made from high silicon aluminum J Piston in 19258602 Piston in 88958602 Piston in 88958603 604 Page 13 Engine Components Continued Cylinder Heads aa P N 12558060 Photo s show the cast iron cylinder head amp combustion chamber used on the 602 engine Head casting number is 10239906 or 12558062 Valve sizes are 1 94 int
21. check for correct rocker ratio The p n for the fixture is 88958663 Page 31 P amp G Test Procedure The P G tester is used to check engine displacement This is a quick on site tool for checking displacement to determine if it is in the allowable cubic inch range Important Information The P G tester must be Kept clean Before each use lubricate the nylon piston tube and o ring with fine oil If tester is to be used for continuous testing it should be oiled after every tenth 10 engine is checked Engine Preparation e Remove all spark plugs e Select the cylinder number to be checked e Have the crew chief remove the both rocker arms and both push rods from selected cylinder Testing Procedures e Insert the spark plug screw adapter into the selected cylinder If this operation is done by the crew chief make sure that no washers or spacers are added to the adapter e Make sure that the nylon piston is bottomed out in the tester tube Insert the push rod gently into the tube and slide the piston to the bottom of the tube e Note the engine temperature as this will be needed to determine the total cubic inch displacement and for the Whistler Test e Important If the engine is cold use the same temperature as the outdoor temperature to read the listed cubic inch number adjacent to the temperature If the engine temperature is warmer than the outdoor temperature read the correction factor on the chart e With the i
22. d and if the engine has been excessively over revved Itis acceptable to add maximum of a 020 shim when valve seats are recut or to get spring pressures back to proper factory specifications Care must be taken to make sure retainer to guide clearance is adequate No Titanium Retainers Allowed Lbs Installed Heights 80s 101lbs 101lbs _ Opna 6 20 3o mo Open Pressure Gs A 195lbs_ 260s 260bs _ Coisa o 0 om a WireDamier SC me oe Page 21 Engine Specifications Continued 88958602 19258602 Engine Camshaft Specifications P N 24502476 camshaft is installed in a 602 engines It is a flat tappet camshaft and uses standard hydraulic lifters See section on valve lash for proper lash procedure Valve Lift 435 intake and 460 exhaust Duration 050 212 degrees intake and 222 degrees exhaust Cam lobe centerline is 112 5 degrees Intake lobe lift 290 Exhaust lobe lift 307 Intake base circle radius 633 Exhaust base circle radius 616 Dowel pin hole Retarded 5 degrees from centerline of 1 cylinder exhaust lobe advanced 107 5 degrees from centerline of 1 cylinder intake lobe 107 5 5 112 5 degrees lobe separation Note 010 all dimensions and 5 degrees angularity Shown below is a graph of the cam profile for cam p n 24502476 as used in 88958602 and 19258602 engines Lex k p 16 l0 VA
23. d that they were no longer able to continue to produce the piston This was a business decision based on the material availability and process used in manufacturing the piston General Motors and the supplier were aware of the implications to the circle track engine program and tried to find an alternative method to make this piston The results of the investigation soon boiled down to one of two choices Either change the piston to a more commonly available material or increase the cost of the engine significantly Cost is a major factor in the success of the engine program so the only real choice was to change the piston material and leave the cost of the engine unchanged Due to the piston change the crankshaft balance also had to change There was initially a concern that there would be a possible power difference or advantage between the two piston designs so GM began some extensive testing to find out The results of this testing proved that no perceivable advantage or disadvantage could be measured between engines equipped with either piston design General Motors decided that since parts in the engine are slightly different and that these parts of the engine will not interchange with each other there had to be a part number change to the engine itself Since the history of the crate engine program has shown that 8602 the last 4 digits of the original 88958602 GM part number was so entrenched in the racing community the decision was mad
24. d to be reliable and withstand normal racing use Following these guidelines will ensure that horsepower gains will be minimal on rebuilds Rebuild Sealing Bolts Contact your local track and or the track s authorized rebuilder when you need to have your engine serviced They will be responsible for resealing the engine for competition and may wish to incorporate their own sealing methods NOTE Effective June 1 2008 GM will no longer provide RM bolts for resealing rebuilt engines If your track is going to continue to allow rebuilds they should use an alternate sealing method as described later in this manual on page 30 Page 19 Engine Specifications Continued Valve seat Machining This drawing covers the valve amp valve seat machining angles amp widths as well as factory valve margin Note No modifications should be allowed to factory valve seat machining angles to increase flow 1 Refer to the chart A B C for proper valve angles 2 Refer to the chart D E F for seat machining angles gt 7 ND VALVE SEAT 3 Refer to the chart H G J for valve amp seat widths 5 Refer to chart K for valve REFER TO CHART TOR JEC if iCATION s margin Factory Valve Angle Specifications 88958603 88958604 Notes No modifications allowed to factory valve seat machining angles to increase flow No angle milling of cylinder heads to increase compression ratio Valve Angle from deck to v
25. e to search for an available part number that used the same last 4 digits Thus the new part number became 19258602 So no matter what 8602 engine you or your competitor may have under the hood be certain that the playing field is still as level as it always was This technical manual has been modified to show where this change designates a physical difference between the two engine part numbers Page 41
26. gnition off crank the engine at cranking speed for approximately 2 seconds or until the engine has been spun at cranking speed approximately 10 times e Read the number where the nylon piston stops Convert this number to cubic inch displacement using the P amp G Conversion Chart e Maximum allowable cubic inch displacement for Chevy is 350 0 o If on conversion from P amp G Conversion Chart is larger than maximum allowable reading retest immediately If reading is still over the legal maximum allowable limit the Whistler Test or cc testing of the heads is necessary Page 32 Whistler Procedure The Whistler measures combustion chamber volume Using the volume achieved with the tester along with the chart provided by the company you will know the correct engine displacement Measuring Combustion Chamber Volume for Engine Displacement Requirements e 110v Power supply e Portable Air Tank or Compressor Engine Preparation e Remove spark plug e With ignition off and distributor unplugged crank engine to locate Top Dead Center TDC of piston in selected cylinder e Purge any remaining gas vapors from selected cylinder using compressed air e Insert Whistler adapter into spark plug hole o When selecting cylinder to test be aware that some engines require the removal of the header to accommodate the insertion of the whistler probe e Check water temperature via gauge or thermometer Testing Procedures e Plug Whistler into 110 v
27. ining has on the engine Make sure your engine re builder follows these specifications Page 17 Engine Specifications Continued Factory Engine Specifications New a 88958603 88958604 Compression Raio om wm se 9 025 4 001 9 025 4 001 9 025 00T Piston Type Cast Aluminum _HiSilicon Alum HrSilicon Alum _ Diameter 3o 399 3999 3 908 3 900 Valve Reliet Type 4relieis 4relieis areles Dished or Dome Disha Fa Fa Piston Weight Piston Only 508 512 grams 533 grams 533 grams PistonPnWeigm mangans O OO O O O O OO O SSCS Connecting Rod Lower End 424 1 Grams 424 1 Grams 424 1 Grams _ A74 510 A74 510 RockerArmRato 5 5 5 e e E Cylinder Head Type Tron Vores Aluminum Aluminum ombuston Chamber Ces o ta a o eo o o a Intake Pontes omoa mw w w Easits ate ONN Note signifies 19258602 engine part specification No Deck Surfacing after 1st Rebuild No Angle Milling of Cylinder Heads to Increase Compression Ratio No Modifications to Crank Rods or Pistons Page 18 Engine Specifications Continued Recommended Rebuild Specifications amp Tolerances 88958603 88958604 Maximum Bore Allowed Maximum of 008 all Bores be ee Otherwise new block required andard Block Deck Heig 001 E a Maximum Deck Surfacing of Block 005 005 005 Minimum Block Deck Height 00r 9020 9 020 0020 Minimun
28. installed on 603 amp 604 engines 12342089 steel cover 12562818 plastic cover Page 15 Engine Components Continued Rocker Arms The photo at far left show the stamped steel rockers and kool nuts that are installed on the 88958602 amp 88958603 engines The photo on the immediate left shows the kool nut used on all 19258602 engines and any 88958603 engine built after May 1 2010 Rocker arm adjustment is critical See page 9 This photo shows the aluminum roller rocker arms that are installed on 604 engines 602 amp 603 engines use stamped steel rocker arms Rocker arm adjustment is critical See page 9 Oil Pans The 602 engine uses an 8 quart pan including filter that is 8 deep The sump is 9 2 long and 11 wide It fits stock front sub cars with stock engine location The right side of the pan is kicked out 3 1 4 and has 3 trap doors to control oil It has a built in crankshaft scraper and comes with a louvered windage tray The 603 amp 604 engines use an 8 quart pan including filter that is 7 deep The sump is 12 long and 14 wide It fits stock Camaro front subs and most fabricated subs with stock engine location It has 6 trap doors for oil control 3 crankshaft scrapers oil temp fitting and a louvered windage tray Below is a photo of the louvered windage tray Photo of the 603 amp 604 oil pan Photo of the louvered windage tray Page 16 Engine Specificatio
29. ion GM Performance Parts is committed to providing proven innovative performance technology that is truly More than just Power GM Performance Parts are engineered developed and tested by the factory to exceed your expectations for fit and function To contact us call 1 800 577 6888 for the GM Performance Parts authorized Center near you or visit our website at www gmperformanceparts com This book provides general information on components and procedures that may be useful for technical inspection of the engines It is also intended as a guide for rebuilding specifications Refer to service manual for comprehensive and detailed service practices Observe all safety precautions and warnings in the service manual for installation in the vehicle Wear eye protection and appropriate protective clothing When working under or around the vehicle support it securely with jack stands Use only the proper tools Exercise extreme caution when working with flammable corrosive and hazardous liquids and materials Some procedures require special equipment and skills If you do not have the appropriate training expertise and tools to perform any part of the installation then contact a professional Legal Information This publication is intended to provide information about your circle track engine and related components The publication also describes procedures and modifications that may be useful during the installation It is not intended to
30. logo installed Page 30 Tech Inspection Procedures Continued One of the earliest series to embrace the circle track crate engine program was the USPRO Series now known as the ASA Late Model Series GM Racing and GM Performance Parts has worked with them to provide some of the procedures listed below Refer to the actual instructions from each manufacture for 100 accuracy of the test procedures These are only guidelines P amp G Procedure www precisionmeasure com The P amp G tester is one of the best on site checks of checking engine displacement It provides a means to check engine displacement without tearing down the engine Note Engine temperature is critical with this test Whistler Procedure www katechengines com The Whistler is used to check compression ratio It s a tool used to check compression ratio of completely assembled engines at the track Note Engine temperature is critical with this test Valve Spring Inspection WWwW moroso com Valve springs are an area that teams try and increase the spring pressure to increase PRM limits of the engine This sheet covers a quick way to check spring pressures on the engine Refer to the spring chart for proper specifications Moroso P N 62391 spring rate checker Rocker Arm Testing 604 engine only Contact local GM dealer GM sells a rocker arm checking fixture It s a simple fixture for testing the roller rockers on the 604 engine This page covers how to
31. lves 5 Adjust the distributor timing to recommended specifications 6 Adjust Carburetor settings Idle mixture screws base idle floats etc 7 After first 30 minutes of the engine running re set ignition timing and carb adjustments 8 Drive the vehicle at varying speeds and loads for first 30 laps Be sure not to use a lot of throttle or high rpm s 9 Run 5 6 medium throttle accelerations to about 4500 rpm and letting off in gear and coasting back down to 2000 rpm 10 Run a couple of hard throttle acceleration to about 5000 rpm then letting off in gear and coasting back down to 2000 rpm 11 Change the oil and filter a PF1218 AC Delco oil filter P N 25160561 or PF45 P N 25324052 and Mobil 1 Synthetic oil P N 12347284 are recommended 12 Drive the next 25 laps without high rpm s below 5000 rpm hard use or extended periods of high loading 13 Change the oil and filter again 14 Your engine is now ready for racing Page 10 Tune Up Specifications Tune Up Specifications s C Description Engine 8602 8603 8604 Spark Pug Gap oso oo Recommended Valve Lash Distributor Advance Settings Mechanical Advance Vacuum Advance Not Used Recommended Header Size 1 5 8 to 1 3 4 stepped header with 3 1 2 collector 33 total length NOTES Page 11 Tune Up Specifications Continued Carburetor amp Adjustments The Holley 80541 1 carburetor is rated at 650 cfm Tr
32. ncluded in this section are proper torque sequence guidelines GM has spent extensive time on engineering metallurgy and physical testing to achieve proper clamping loads on bolts Any deviation of these specifications will affect the life of the engine Sealers also affect clamp loads The proper sealer should be used for each bolt where applicable It is imperative that torque specifications and sealer recommendations be followed closely All surfaces must be clean and free of debris All tapped holes should have thread chasers run through them to clean old residue from the threads before re assembly Make sure you wear proper eye protection at all times Because the cylinder block does not have blind head bolts all the head bolts will require sealer Factory new head bolts come with the proper sealer applied Break off sealing bolts installed from the factory have sealer applied Replacement sealing bolts do not have sealer factory applied Main Cap Bolts amp Engine Galley Plugs Use light engine oil or CMD 3 on all main cap bolts during assembly Use P N 12346004 Teflon sealer on all oil passageway galley plugs Do not over apply as it may clog lifters and other engine components See next page for torque specifications Head and Intake Bolts 1 Use P N 12346004 Teflon sealer on head bolts and intake bolts 2 Use P N 12346192 in tube form or 12346193 in cartridge form for intake china rails A bead 3 8 wide and 3 8 tall should be
33. ns This section covers recommended rebuild specifications All three engines are assembled with brand new parts Each engine will be within a tight horsepower range from the factory Customers typically get 2 seasons of service from each new engine GM does not recommend rebuilding engines We recommend purchasing a new engine and selling the used engine to the hot rod street rod or drag racing community This will ensure 100 integrity of the program If rebuilds are allowed It is up to the track owner or sanctioning body to manage the rebuilders and closely monitor the rebuilt engines The key to maintaining close competition between new engines and rebuilt engines is to make sure rebuild specifications are kept close to factory tolerances These specifications are only guidelines If the engine is rebuilt to these specifications minimal horsepower differences should be noticed These specifications also provide a reference point for inspection of suspected modifications to the factory engine Valve angles and depths are critical to valve life and horsepower levels The valve seat width and angle affects airflow It s also a crucial part of removing heat from the valve and extending valve life The balance of keeping good air flow in all the lift ranges as well as getting the heat out of the valve is necessary to extend the life of the valve and seat Engine rpm s also affect the valve and seat life When the harmonics of the valvet
34. olt power supply e Turn on Whistler e Adjust display as follows o Re Set the 3 switches as follows Left hand switch set for numbers 4 6 8 Center switch has 3 functions e Center position Set Temperature of engine e Bottom position Set displacement as determined by P amp G test o Maximum Reading for Chevy 350 0 Top Position this is where the actual reading will appear o Right hand switch is used to set reading either up or down to change readings e Once the engine temperature and engine cubic inches have been entered move the center switch to top Insert whistler probe into adapter in selected cylinder Make sure that the piston is at TDC Hook up air line to portable air tank Adjust air flow to 20 SCFH Rotate engine slowly in either direction to determine if TDC has been reached At TDC note the highest compression ration reading Rotate the engine slowly in the other direction to determine the highest reading Maximum allowable static reading is 10 1 as shown on the readout If the reading is larger cc the heads to determine the legality of the engine Page 33 Valve Spring Inspection Procedure This section helps identify those teams that have changed valve springs in an effort to gain additional rpm s It is important to keep rpm s within GM recommended numbers Engine life and wear is severely reduced for every 100 rpm s that an engine is over revved Purpose Check for proper stock
35. ou must use the correct balanced flywheel The front balancers on the circle track crate engines are zero balanced Therefore the internal components of the engine are zero balanced like a pre 1986 engine The only difference is the rear flywheel has a counterbalance This is because the rear of the crankshaft is machined for the 1pc seal One piece rear seal engines do not have the counterbalanced flange like pre 1986 engines Photo to the left shows a flexplate that fits all three engines The counterweight is shown in the 10 o clock area of the photo It is welded in the proper location which makes sure the engine balance is correct Make sure whatever flywheel you use has a counterbalance on it or the engine will have a vibration This photo shows an aftermarket drive hub It combines the ring gear transmission input spline and proper counterbalance location This is a great photo of how one aftermarket manufacturer address s the external balance required at the rear of the engine When the one piece seal was introduced GM implemented a change to the bolt pattern diameter The bolt pattern diameter changed from 3 1 4 to 3 This was done to insure that older flexplates would not be installed by mistake and cause imbalance issues Make sure if you are using an aftermarket component it has the correct balance Page 27 Flywheel amp Transmission Components Transmission Installation Components 889586
36. ow for each rocker arm Valve Lash Adjustment 1 Position engine at TDC on 1 cylinder in firing position Adjust Intake valves on 2 amp 7 cylinders Adjust Exhaust valve on 4 amp 8 cylinders 2 Rotate Crankshaft 1 2 Revolution Clockwise Adjust Intake Valves on 1 amp 8 cylinders Adjust Exhaust Valves on 3 amp 6 cylinders 3 Rotate Crankshaft 12 Revolution Clockwise Adjust Intake Valves on 3 amp 4 cylinders Adjust Exhaust Valves on 5 amp 7 cylinders 4 Rotate Crankshaft 2 Revolution Clockwise Adjust Intake Valves on 5 amp 6 cylinders Adjust Exhaust Valves on 1 amp 2 cylinders Reinstall valve covers connect distributor and start engine to check for loose valve lash Page 9 Recommended Break In Procedure Start up is critical to ensure engine life This procedure was written with the intent to provide a quick reference and guideline to starting a new or rebuilt engine if a dyno is not available If you are using a dyno refer to the dyno operator s guidelines for start up and initial break in of the engine 1 Safety First Make sure you have proper tools as well as eye protection If the car is on the ground be sure the wheels are chocked and the transmission is in neutral 2 Be sure to check the oil level in the engine and prime the oil system 3 Run the engine between 2 000 and 2 500 rpm with no load for first 30 minutes 4 Refer to valve lash procedure and lash va
37. rain overcomes the valve spring the valve bounces off the seat and the valvetrain becomes unstable this reduces the amount of time the valve contacts the seat and transfers heat Every millisecond the valve is bouncing it reduces the seat contact and heat transfer RPM recommendations need to be strictly enforced to prolong valve life These recommendations were tested and designed to extend the life of the valve train components as well as the complete engine Do not exceed the recommended rpm limits The following page covers the details of the valve seat area These are the factory machining specifications Anytime the valve seat and valve is touched up it may affect the height of the valve in the combustion chamber This will have a negative effect on the compression ratio but not enough to make a large horsepower difference Reference the page on valve springs for factory specifications when new Valve springs lose strength during the life of an engine The major factor in reducing valve spring life is heat therefore no oil restrictors are installed in the engine Oil restrictors are not necessary when the rpm s are kept within factory recommendations All three engines have excellent drain back to the oil pan As long as the breathers are functioning properly and the engine has minimal ring blow by oil drainage to the pan will be good Some engine builders have learned from experience the negative effects that improper valve seat mach
38. replace the comprehensive service manuals or parts catalogs which cover General Motors engines and components Rather it is designed to provide supplemental information in areas of interest and to do it yourself enthusiasts and mechanics This publication pertains to engines and vehicles which are used off the public highways except where specifically noted otherwise Federal law restricts the removal of any part of a federally required emission control system on motor vehicles Further many states have enacted laws which prohibit tampering with or modifying any required emission or noise control system Vehicles which are not operated on public highways are generally exempt from most regulations As are some special interest and pre emission vehicles The reader is strongly urged to check all applicable local and state laws Page 3 History GM has a long history of providing the engine of choice for circle track racing The introduction of the small block Chevy in 1955 started it all Production parts were durable and the engines were plentiful In the 1960 s GM started producing HD parts for racing activities and a whole industry was Started Over time the competitive nature of racing drove costs increasingly higher and sanctioning bodies found it increasingly difficult to police the competitors In the 1990 s several tracks and individuals took GM s successful crate engines designed for the street and adapted them for circle tr
39. stall additional seals by installing a couple of drilled bolts in key locations intake front cover amp oil pan then run a stainless wire between the bolts and use a crimp seal The crimp seal can be as simple as the Shown is Drill bolt fixture stainless wire amp safety wire pliers track logo on a pair of vice grips where you crimp a large fishing sinker Some bolts can be purchase off the shelf already drilled making installation easier Wire Lock Seals One of the major sanctioning bodies uses seals that involve a seal that locks the wire inside preventing removal It also has enough area on the lock to serialize and or add a logo This sanctioning body has tough rules regarding rebuilds does extensive tech inspections There resealed engines are monitored closely They also use the cup plug as shown below as a secondary seal Both seals are marked serialized and registered Shown is a Wire lock seal www vmsproducts net www stoffel com Cup plug seals This method uses a special base that is secured by the bolt A cap is pressed on to the base and encapsulates the bolt head Fingers on the base grab the outer rim of the cup and prevent removal without signs of damage These seals can be serialized and or a logo added They are simple to use when a standard size bolt is required It is more difficult when you have specialty F or in tight areas www americancasting com Cup plug system that can be serialized and track
40. t 005 O S 6 12507985 12524205 6 12528818 8 12528818 NS NS Piston High limit 1 po 12514102 88894280 10159437 10159437 Valve Intake Brea 10241743 10241743 10241743 12555331 Valve Exhaust 8 req 12550909 12550909 12550909 12551313 12495494 note 12495494 note 12495490 note 3 12495490 note 3 12495490 note 3 Factory Rebuild Gasket List o Oil Pan Gasket One piece gasket 10108676 19212594 10108676 10108676 N S Rear Main Sea q25sa314 1255a314 12554314 12554314 Seal Intake Valve Water Outlet Gasket 10105135 10105135 10105135 10105135 Gasket Fuel Pump Cover Opening _ 12560223 12560223 12560223 12560223 Gasket Fuel Pump 10114141 10114141 10114141 f 10114141 Oil Filter_PF 25 25324052 25324052 25324052 25324052 __ Note 1 12495494 contains 16 of 12551483 springs Note 2 Requires 16 pcs of 1916961 HD retainers or 1pc 19171528 kit Note 3 12495490 contains 16 of 10089648 rocker arms Note 4 19210728 contains 16 of 19210724 rocker arms Page 38 Engine Parts Lists Continued Factory Service Bolt List Bolt Timing Cover Plastic Cover Short Bolt liming Cover Plastic cover Long TI Q O a O lt 0 D lt O D WwW o E i Continued Bolts Intake 68958603 continued s889170 Bolts Intake 88958603 continued 0s9 Bolt Balancer 3815833 381593 3815933 Washer
41. thin specified limits Valve Lash Valve lash is critical Read the procedures closely All three engines do not have oil restrictorse This insures ample oil is available to cool the valve springs and pull heat from the valves Break In Procedures GM has detailed break in procedures to ensure the life of your engine is maximized Failure to follow these break in procedures will shorten the life of the engine Make sure you read this page completely before attempting to start your new engine Tune Up Specifications Tune up specifications are provided for each engine to insure that they are tuned to factory specifications Altitude humidity and other factors will affect performance Do not increase timing more than factory recommendations All three engines have had extensive dyno amp track testing to maximize horsepower using these parameters Maximum performance will be achieved if you keep the tune up within factory recommendations RPM Limits RPM limits are critical to engine life Catastrophic engine failure can occur if the engines are run above the factory recommended limits Extensive dyno amp track testing has determined the limits of the engine Under no circumstances is it recommended to exceed these limits GM recommends that all sanctioning bodies track operators or promoters have rey limits written in their rule book Maximum limit for 602 engine is 5500 rpm Maximum limit for 603 engine is 5800 rpm Maximum limit for 604
42. undation The 10 1 1 compression ratio from the aluminum heads makes good power The 7 deep oil pan holds 8 quarts including the filter The engine has a dual plane medium rise aluminum intake This engine weighs 400 Ibs as delivered Page 6 GM Circle Track Engines continued Notes P N 88959604 604 88958604 is rated at 400 hp 5500 rpm It makes 400 ft lbs torque 4500 rpm It fits well in late models and other classes that run on longer tracks The engine comes complete intake to pan It does not include distributor flywheel or water pump The 4 bolt block steel crank powder metal rods and high silicon pistons make a great foundation The 9 6 1 compression ratio with Fast Burn aluminum heads and roller rockers make great power and lots of torque The 7 deep oil pan holds 8 quarts including the filter This engine has a high rise single plane aluminum intake manifold This engine weighs 375 Ibs as delivered Page 7 Installation Instructions Each engine comes with detailed instruction sheets This section includes some of the information that is included in those instruction sheets It is imperative that the startup procedures are followed before starting the engine Failure to do so may result in catastrophic engine failure These procedures are designed to ensure engines are properly broke in for maximum engine life Two key factors affect engine life proper valve lash and keeping rpm s wi
43. valve spring specifications Use Moroso p n 62390 Step 1 Have the crew chief remove all debris in and around the engine Step 2 Have the crew chief remove the valve cover being careful not to contaminate the cylinder head Step 3 Have the crew chief remove both rocker arms from the selected cylinder amp make sure piston is at BDC Step 4 Slide the Moroso valve spring tester into position so that intake valve spring sits in tester pocket Step 5 Pull the handle to compress the valve spring to full compression and note the reading Repeat the test for the exhaust valve spring and note the reading Step 6 Refer to chart in rebuild section for correct valve spring pressures for the intake amp exhaust Use the space below to reference the numbers for your application Int Exh Page 34 Rocker Arm Check Procedure GM Racing designed a checking fixture for the aluminum roller rockers used on 604 engines It can be purchased at your local dealer The p n is 88958663 The GM P N 88958663 roller rocker inspection fixture is designed as a quick Go No Go gauge for verifying roller rocker arm ratio s It does not include rocker arms Both Sides of the fixture are marked for easy identification of a 1 5 or 1 6 rocker arm ratio The fixture is designed to check a GM roller rocker arm by placing the rocker arm on the stud and seating the roller tip on the pedestal then checking the pushrod to the rocker arm cup seat
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