Instructions - Demon Fuel Systems
Contents
1. 7 HouanestnedetdueTustsescudesadetdvssesssncseduetuGuaasrsterticscdetncseecte 7 8 Priming the Carburetor e ra A aa aoaaa E a oaaae aa dn i iata aeaa 8 Mechanical Fuel a AAE AA 8 Electric Fuel PUMP 8 Ladies and Gentlemen Start Your 8 Preliminary Tuning Adjustments 8 Curb Idle Speed and Mixture 8 PuehiPreSSure EEN 9 PERFORMANCE TUNING AND 10 Secondaty Air Valve baad 10 Accelerator Pump Tuning 10 Main Metering TUNING Sec face coos oad enol fede case teed ened ARETE RA RAAE E hectare 12. 4 Repair as necessary 5 Secondary Air Door or Goggle Valve stuck or partially open 5 Find cause and repair 17 Warm Engine Hesitation under 1 Defective accelerator pump 1 Look for dirt in pump nozzles swollen cup from bad gas or check ball missing or stuck 2 Metering rods sticking or binding 2 Repair as necessary 3 Vacuum leak 3 Locate leak and repair heavy throttle 4 Float level setting very low 4 Reset to factory specs Condition Dead spot amp Cont stumble May backfire or spit 5 Plugged up fuel filter defective 5 Inspect and repair as necessary back fuel pump or swollen or kinked lines 6 Secondary air valve set wrong 6 Check amp adjust the secondary air valve spring 7 Ignition timing retarded 7 Set to factory specs Make sure advancing correctly 1 Plugged exhaust 1 Check exhaust Look for plugged catalytic converter bad muffler baffle kinked or crimped pipe dirt or other foreign matter in pipe 2 Clogged gas tank vent or fuel 2 Remove gas cap amp see if performance improves If so clean venting system or replace the gas cap Check the charcoal canister hoses to it amp any check valves Check the electric vent valve on the carb if there is one amp make sure it is getting power at the right time 3 Ignition timing retarded 3 Check timing at idle and also for full adv
3. CARBURETION STREET CARBURETOR INSTRUCTION MANUAL LIT701 nt D Table of Contents duanestnesdanstedsctesereececetbeedensentecnteniyeent ees 3 Recommended Parts and 3 Removal of Existing Carburetor 3 Installation of Street Demon Carburetor c ssssssssssssssssssesssssesssssssssesssssscssssscsssssesesesasssesassscsussossuesovesesosenesasesensassseasseseassess 4 Connecting the Throttle 5 Connecting the Transmission 5 GM 50 20084 700 4 2 2 2 anaana rme aeaaeae aaraa enaa kaa ea suetcetedeudcnsessencebseetudeansvetcstidetdenawcseset 5 Ford resenteesdenciessevecueessencdiesevenneedeencdesedecberteceauerreseetes 6 Chrysler amp sccccesceeresscercctiesedteccelesduteecenecceceeteutnesucecetatesissneshendescuetsiunesteluesaceadetsastsuceedeutsduaasveteehiceadeaccvende 6 Va umi LINGS A
4. This can damage the floats and cause flooding Remember to check for leaks The engine should now be ready to start with a minimal amount of cold cranking Ladies and Gentlemen Start Your Engines Get a helper Unless your car can be started from the engine compartment starting your engine for the first time should always be performed with an assistant A second set of eyes to watch for fuel leaks can be invaluable Before engaging the ignition depress the throttle fully and release once or twice Now attempt to start the engine If the engine does not fire under reasonable cranking stop cranking and repeat the process once again Each engine may require a different number of pump shots to ease starting Determine what is best for your engine Allow the engine to achieve normal operating temperature before attempting final adjustments to the idle speed or idle mixture settings It is however acceptable to make fuel pressure adjustments during the warm up period Preliminary Tuning and Adjustments The following preliminary adjustments should be made prior to attempting to drive the vehicle Curb Idle Speed and Mixture Adjustments Fine tuning of the idle speed and mixture must be done with the engine at or near operating temperature A good rule of thumb is to not attempt adjustments until the engine has achieved 160 degrees water temperature Adjusting the engine cold will usually result in a rich mixture at normal operating temperatur
5. 14 4 Disconnect the choke linkage by carefully removing the E ring retainer from the choke rod Fig 22 5 Disconnect the accelerator pump rod from the pump arm by carefully removing the c clip Fig 23 4 Figure 22 Figure 23 6 Remove the six Phillips head screws from the bottom of the carburetor as circled in Fig 24 7 The carburetor air horn may now be carefully removed from the main body fuel bowl assembly 8 Invert the air horn to access the primary and secondary metering jets Fig 25 9 Re assemble in reverse order of removal Figure 24 Figure 25 Winter Fuel Different fuels are used in the United States in the summer and winter These fuels can even differ depending on what part of the country you are in Winter fuels have a higher Reid Vapor Pressure than summer fuels In other words the fuel boils at a lower temperature than that of a summer blend Most of the time this does not cause issues with drivability however in early fall or late spring when summer temperatures may still be present and winter fuels are in use it may cause drivability issues The most common problem observed is the fuel boiling in the fuel bowl and percolating out of the vent tubes after the engine is shut down after a drive Another less common issue is the fuel evaporating in the fuel line or also known as vapor lock The best thing that can be done if this is experienced is to isolate the fuel lines
6. a weaker spring A heavier spring will allow the piston to rise in its bore sooner therefore placing the rich step of the metering rod into the jet orifice eliminating the lean spot The chart below outlines the available step up springs Spring Color Blue Yellow Orange Green Silver Rating in Hg 3 Hg 4 Hg 5 9 6 9 8 Hg Wide Open Throttle Tuning See next page for instructions on changing rods springs and jets Wide open throttle WOT tuning is best performed after the steady state cruise and part throttle acceleration is complete WOT tuning is best performed using a dyno or at the drag strip DO NOT attempt to perform wide open throttle tuning on the street Using a helper AFR or vacuum gauge readings should be taken at WOT to determine if the engine is running rich or lean Tuning the WOT is done by changing the secondary metering jets If the engine is to lean go up a couple of steps in the secondary metering jets if it is too rich go down a couple of sizes in the secondary metering jets It is not recommended to go more than two sizes at a time so that it is easier to monitor the changes 13 Long Duration Camshaft Tuning Long duration or radical camshafts generally need more idle air than a stock or mild camshaft and require the throttle plates to be opened more than that of a stock or mild engine Excessive throttle opening at idle coupled with low manifold vacuum makes it possible that
7. and carburetor from excess heat by using a phenolic spacer under the carburetor and insulating the fuel lines If you store your vehicle over the winter it is highly advised that a fuel stabilizer such as STA BIL is added prior to storing 15 Street Demon carburetors do not require extensive maintenance They are made from aluminum so over time the shiny Care and Cleaning appearance can dull Any quality aluminum cleaner and polish can be used to bring the shine back to as new condition Always clean the part first with a mild soap and water or non vinegar based window cleaner then polish as instructed by the polish manufacturer Always use a new microfiber cloth for polishing or unwanted scratches can occur The composite fuel bowl on the part 1902 Street Demon does not require any type of polishing cleaning with a mild soap and water will bring it back to new condition Troubleshooting PROBLEM CONDITION POSSIBLE CAUSE CORRECTION 1 Choke not closing 1 Inspect choke adjustment and for something binding Adjust if necessary 2 Choke linkage binding 2 Lube with WD 40 and check for something bent Adjust if necessary 3 No gas carb 3 Check fuel delivery Look for plugged filter or clogged lines Engine cranks but bad pump stuck needle amp seat and fuel pressure will not start 4 Accelerator pump defective or 4 Replace the pump Problem
8. factory recommendations amp check float weight replace if necessary 17 Ignition problems or needs a tune up 17 Do complete tune up amp physically inspect the cap rotor wires coil plugs points etc in addition to checking on the scope 18 Gas pours out when engine turned off 1 Charcoal canister is saturated with gas 1 Replace the charcoal canister 2 Winter fuel 2 Isolate heat to carburetor or get summer fuel is possible 3 Kinked hoses in venting system 3 Replace the kinked hoses with correct kind 4 Stuck or blocked check valves in the vent hoses or elsewhere in the system 4 Replace the check valves 5 Gas tank vent is blocked 5 Fix or replace the gas cap if vent is in the cap 6 Gas line located too close to a heat source such as a radiator hose or exhaust manifold 6 This causes the fuel to expand amp be forced past the needle amp seat Also fuel can boil in the carb if there are improper or missing gaskets or spacers between the carb amp manifold A heat riser stuck in the closed position will also cause boiling and flooding 1 Dirt stuck on tip of the needle 1 Clean the tip off carefully or replace the needle and seat amp Flooding amp seat clean the entire fuel system out Check for defect canister causing debris or fuel contamination 2 Idle speed is set too fast 2 Reduce
9. is usually caused by bad gas worn out dirt in gas or vacuum leak or ignition problems 5 No spark or engine problems 5 Diagnose amp correct the problem such as bad compression 1 Choke not closing properly 1 See notes above Adjust choke if necessary 2 Big vacuum leak on engine 2 Use vacuum gauge to check Fix the leak You may have put somewhere the base gasket on wrong or it is the wrong one for this carb amp engine combination Engine starts then dies within a few 3 Fast idle RPM set too slow 3 Adjust to recommended RPM Cold Starting seconds 4 Low fuel delivery 4 Correct delivery to carb Usually it is a plugged up filter 5 Electrical or compression 5 Do complete tune up amp diagnosis Fix the problem problems on the engine 6 Float level set very low 6 Check amp adjust float level to factory specs Engine normally 1 Choke setting too lean 1 Richen choke by adjusting cap counter clockwise starts OK but then dies backing out driveway or at first stop sign After that it runs OK Engine starts OK 1 Choke set too rich 1 Lean choke by adjusting cap clockwise increases RPM then gets too slow 2 Slow flooding 2 Fix cause of flooding with 3 Float level very high 3 Rare Set to factory specs Engine starts then 1 Big vacuum leak somewhere n ee ea ns forgotten to raGes tora few up a hose somewhere Base gasket may be wrong one or on wrong seconds and then
10. otherwise transferable There are no warranties that extend beyond those stated herein Demon Carburetion offers no other warranties expressed or implied beyond this Limited Warranty In the event of an alleged defect in material or workmanship the responsibility of Demon Carburetion is strictly limited to the repair or replacement of the defective product Demon Carburetion has no other obligation expressed or implied Final warranty determination will be in the sole discretion of Demon Carburetion Demon Carburetion shall not be responsible for a actual or alleged labor transportation or other incidental charges or b actual or alleged consequential or other damages incurred by use of any product of Demon Carburetion To initiate the warranty process the consumer must return the alleged defective product to the place of purchase with a dated receipt and completed applicable warranty claim tag Warranty claims will be rejected if the date of purchase cannot be established by the consumer Do not send products directly to Demon Carburetion Demon Carburetion assumes no responsibility for products sent directly to Demon Carburetion This Limited Warranty sets forth specific legal rights The consumer may have other rights as a result of variations in state laws or provincial laws This Limited Warranty supersedes all prior warranty statements DEMON CARBURETION NEW PRODUCT Demon Carburetion warrants its new
11. products to be free from defects in material and workmanship for a period of 90 days from date of purchase Demon Carburetion Limited Warranty specifically does not apply to products which have been a modified or altered in any way b subjected to adverse conditions such as misuse neglect accident improper installation or adjustment dirt or other contaminants water corrosion or faulty repair or c used in other than those applications recommended by Demon Carburetion Demon Carburetion also does not warrant and disclaims all liability for products used in racing activities and or applications other than those specifically recommended in the current brand catalog NOTE IF YOU HAVE ANY QUESTIONS ABOUT THE SETUP OR TUNING OF THIS CARBURETOR PLEASE CONTACT THE DEMON CARBURETOR TECHNICAL DEPARTMENT DIRECTLY AT 270 901 3346 Return Address amp Contact information Demon Carburetion 1801 Russellville Road Bowling Green KY 42101 Ph 270 901 3346 www demoncarbs com 2012 Demon Carburetion All rights reserved LIT701 Revision Date 5 17 12 20
12. 1 Operathon ice ccsat ck sist lca cele eet 11 te eis dees Ste tarsi bei aes isles 12 steady State Cruise a a tient onal nila li ili ileal ar 13 Part Throttle Acceleration Tuning 25 to 75 throttle een neaeeeseeeeeseaeenaeeeseeeenseneeneees 13 Choosing the Correct Metering Rod and Step Up 13 Wide Open Throttle TUMing c ccccsccesseeceseeeeeseeeeeneeeseaeenseeeeneeeesaaeseaneeeneeeeseaesesaaesganeeeeeeessaaesaseeeeneeeeseaesaseaesaseeeeeenaeas 13 Long Duration Camshaft 14 Elevation ee ce nore eens 14 Removal and Installation of Metering Rods Step Up Springs and 14 Metering Rod and Step Up Spring 14 Primary and Secondary Jet 14 Winter PUG aa a te cet ce dente ds cue ew cuneate enticed an dV EE a dv endaen ie cuseeveetaded a A 15 C re and Cleanings st
13. 3 16 vacuum port located on the front of the baseplate is timed ported above butterflies vacuum Ported or timed vacuum for spark advance to occur with throttle opening Hi iy a Direct manifold vacuum 1 4 pipe plug for power for diagnostics brake application Direct manifold accessories or PCV vacuum accesories Figure 8 Electric Choke 1 Connect the electric choke lead supplied to the positive terminal of the choke cap The other end must be connected to a good ignition activated 12 volt source Hookup of this wire is not optional WARNING Connecting the choke cap to the ignition or ignition coil could result in unacceptable choke operation poor fuel economy and possible engine misfiring since the voltage delivered to the spark plugs will be severely reduced by the drain imposed by the choke cap Suitable ignition activated 12 volt sources are most electrical relays as well as the leads to accessories such as windshield wipers DO NOT connect this wire to the original equipment electric choke source This may not be a 12V source 2 Check the voltage source with a volt ohm meter to assure proper voltage and choke operation Provision of a good ground and 12 volt source that can supply enough current to the choke cap is essential for proper choke operation 7 Air Cleaner 1 With some air cleaner configurations it may be necessary to use an air cleaner spacer to provide adequate clea
14. an be run either at idle or wide open throttle at these pressures Be sure your fuel delivery system is properly adjusted and able to maintain volume flow at these pressures Improperly adjusted or inadequate fuel delivery will result in poor performance and possible engine damage Complete the following steps to tune the electric choke j e D 4 LOOSEN THREE SCREWS NEGATIVE POSITIVE Figure 11 Figure 12 Figure 13 1 There are two primary adjustments the fast idle adjustment screw and the choke timing The fast idle adjustment screw controls how far the primary butterflies are open when the choke butterfly is closed or partially closed It controls how fast the engine will idle during cold engine warm up The fast idle adjustment screw is located on the bracket that is screwed to the throttle shaft behind the choke housing Fig 11 Fast idle can be increased by turning the fast idle screw clockwise or decreased by turning it counter clockwise It is important to note that when the choke butterfly is open completely vertical up and down the fast idle adjustment screw must not be holding the primary butterflies open at all In other words when the fast idle adjustment screw is at the lowest step on the fast idle cam it must not be touching or making contact the fast idle cam See Figure 12 for a view of how the fast idle screw rides on the steps of the cam 2 Rotati
15. ance when revved up Look for bad or loose hose hose hooked up to wrong pipe on distributor bad thermal switch leaking vacuum advance can on the distributor a worn breaker plate worn distributor shaft sticky weights point gap closed up etc 4 Clogged air filter 4 Replace air filter 5 Choke not opening 5 Fix choke or power source problem 6 Secondary not opening 6 Check for sticky or bent shaft or linkage Check secondary air door check the spring tension amp metering rods for dragging or sticking 7 Wrong main jets or rods 7 Check and replace as necessary Poor 8 Dragging brakes 8 Fix brake problem Performance No power or bad or Gas gas mileage 9 Low tire pressure 9 Increase tire pressure to factory specs Mileage 10 Automatic Transmission malfunction 10 Diagnose amp fix automatic transmission 11 Wrong or malfunctioning thermostat in cooling system 11 Replace thermostat 12 Blocked or leaking exhaust heat passage in intake manifold 12 Remove manifold amp fix it 13 Defective accessory power steering pump air conditioning compressor etc causing drag on engine 13 Diagnose amp repair or replace the accessory unit 14 Wheels out of alignment 14 Have wheels professionally aligned 15 Poor driving habits 15 Reduce speed quick acceleration screeching around corners etc 16 Float level too high or float partly sunk 16 Set to
16. dies every time 1 Carburetor flooding 1 Fix cause of flooding 2 Choke is closed when engine 2 Find amp fix cause for choke staying closed Check power and is hot ground make sure power wire has a full 12v or something 2 jammed bent check choke linkage to air cleaner clearance Warm Starting 3 No fuel 3 Check fuel delivery volume and pressure Look for clogged Engine cranks but lines filter or pump Check for kinked or swollen fuel lines will not start 4 No air 4 Check for clogged air filter especially after driving through muddy or dusty area 5 Too much air 5 Look for big vacuum leak such as broken hose blown gasket bad power brake diaphragm bad PCV valve Rough Idle 16 Warm Starting Engine starts then dies within a few seconds 1 Choke is staying closed 1 Diagnose and fix choke problem 2 Carburetor flooding 2 Fix cause of flooding 3 Venting system failure 3 Check out entire fuel system venting system including the vent valve on the carb the charcoal canister all hoses amp check valves in the system and any solenoids that trigger the vent system to operate 4 Step Up Piston up in bore 4 Remove step up piston and fix sticking issue or use a lighter Cont step up spring Engine starts then 1 Big vacuum leak somewhere 1 Find the vacuum leak amp fix it Also look for wrong base gasket races for a few or o
17. e It is also helpful to use a tachometer and or a vacuum gauge for setting the idle speed and mixture to obtain the highest idle RPM or highest vacuum reading without adjusting the idle set screw Ensure the engine is at idle with the choke fully open and at operating temperature You may now evaluate the adjustment of the idle mixture screws Fig 9 Turning the screws in clockwise reduces the amount of idle fuel and leans the idle air mixture Backing the screws out counter clockwise increases idle fuel and enriches the idle air mixture The idle mixture screws are preset at the factory and SHOULD NOT need any adjustments however some engines may require more or less fuel at idle To adjust the idle mixture begin by lightly seating both screws and then turning out 2 full turns as a beginning point Next turn each screw 1 8 to 1 4 turn at a time alternating between each screw If idle speed decreases back the screws out 1 8 to 1 4 turn Turn them equally until you achieve the highest possible manifold vacuum or highest idle RPM reading Adjusting the screws to less than 1 full turn open can result in an off idle stumble Once your idle mixture screws are adjusted properly you can now adjust the idle set screw to achieve the desired idle RPM Fig 10 IDLE SET MIXTURE SCREWS ARR SS Figure 9 Figure 10 Fuel Pressure Demon recommends between 5 and 6 PSI fuel pressure at idle Gasoline carburetors c
18. eady state cruising there is enough vacuum to overcome the step up spring tension so the rod is in the down position and the lean step is in the jet It is best to drive the vehicle at a steady state and record the AFR or vacuum gauge reading in 10 MPH increments Once you have the readings you can then determine if the engine is running rich or lean For steady state cruising you should target an AFR of 13 5 to 1 Part Throttle Acceleration Tuning 25 to 75 throttle During part throttle acceleration vacuum in the engine drops and is no longer able to overcome the spring tension and the step up piston will rise as will the metering rod At this point the rich step of the metering rod will be in the jet Have a helper record the AFR or vacuum gauge reading during part throttle acceleration For part throttle acceleration you should target and AFR of 12 5 to 1 Remember if using a vacuum gauge you are tuning to achieve the highest vacuum reading At first it may be a guess whether it is too rich or too lean Once you make a change you will be able to tell by the new vacuum reading if you went the wrong way or not Choosing the Correct Metering Rod and Step Up Springs See next page for instructions on changing rods springs and jets Once you have the readings from the steady state cruising and part throttle acceleration you can now choose the proper metering rod For example your carburetor currently has a metering rod with a 060 lea
19. ealing plate and second flange gasket provided with the carburetor in the proper position on the intake manifold Fig 1 NOTE The sealing plate is required for the proper function of the idle circuit which aids in idle fuel atomization along with a reduction in heat transfer from the intake manifold NOTE If installing the Street Demon a factory cast iron spread bore style manifold a spacer may be required for proper throttle opening 3 Place the carburetor on top of the flange gasket on the manifold Install the hold down nuts and snug down progressively in a crisscross pattern 60 80 in lbs 4 Open and close the throttle a few times to ensure the throttle operates smoothly with no binding or sticking WARNING Over tightening may result in a warped or cracked carburetor throttle body WARNING Any sticking binding or other interference in the throttle linkage could result in uncontrolled engine speed This could result in engine damage or personal injury 5 In some cases the existing fuel line will have to be cut and connected with a length of rubber fuel hose and a clamp The Street Demon carburetor comes with three fuel fittings 5 16 hose barb 3 8 hose barb installed and a 3 8 inverted flare fuel fitting for a hard line Select the appropriate fuel fitting and install into the carburetor making sure to use the new fuel inlet fitting gasket also supplied in the kit Figure 1 Optiona
20. emon is also included in this section Secondary Air Valve Tuning The secondary air valve door is designed to dampen the transition from primary to secondary operation Controlled by a torsion spring the secondary air valve door is tunable to permit seamless primary to secondary throttle response regardless of the throttle rate opening Lock Nut Adjusting Screw amp 5 N F Figure 14 The factory setting for the secondary air valve door is the most common setting which is one full turn counter clockwise after the air valve door is completely closed If tuning is desired using a flat blade screwdriver engage the adjusting screw then loosen the lock nut If the locknut is loosened before engaging the adjustment screw the spring tension will be released Fig 14 turn the adjusting screw counter clockwise to increase spring tension on the door and delay opening Turn the screw clockwise to decrease tension and allow the door to open sooner Tighten the lock nut to hold the adjusted position It is not recommended to go beyond one turn more than the factory setting As an example you experience a hesitation or backfire when the secondaries open This means the secondary air door is opening to quickly so it is necessary to adjust the door tighter counterclockwise until the hesitation disappears It is recommended to only adjust the door turn at a time an retest for the condition CAUTION Adjusting the secondary a
21. erate properly The extra fuel needed by the engine is provided by the metering rods step up piston springs and step up pistons Under a heavy load condition there is not enough vacuum available to overcome the step up spring pressure therefore the piston rises in its bore and in turn raises the metering rod When the rod is up the smaller step or rich step of the rod is in the main jet orifice allowing the extra fuel needed to pass or richen the air fuel mixture so a desirable air fuel ratio is maintained 11 On the other hand when the engine is under a light load such as idle or steady state cruising the engine does not need extra fuel Under light load there is adequate vacuum to overcome the step up spring tension therefore the step up piston stays in the bottom of its bore which also positions the metering rod at the lowest position When the metering rod is down or at its lowest position the large step or lean step of the metering rod is in the main jet orifice restricting fuel flow or leaning out the air fuel mixture so a desirable air fuel ratio is maintained Figure 18 is a cutaway view of the enrichment circuit in a light load condition such as idle or steady state cruising The step up piston is in the bottom of the bore and the lean step of the metering rod is in the jet therefore restricting fuel flow so the desired air fuel ratio is maintained Figure 19 represents the enrichment circuit in a heavy load condition such as wide open t
22. etestacestccuepsetiestenducuensteudsdues Sedeeasteatecteets 16 TrOUDIGESNOOUING aaa a asa a se a a a a a 16 Demon Carburetion Limited Warranty 20 INTRODUCTION Street Demon Carburetors have many unique features that make them one of the best performing carburetors in the market Whether it is street strip performance or just getting the most out of your hot rod the Street Demon will give you optimum performance This manual will discuss the special points and unique features of the carburetor and the correct procedures for proper installation and tuning The goal is to help you understand the thoughts behind the Street Demon and to increase your knowledge of carburetion Please read and understand this manual completely to assure that you get the most out of your new Street Demon carburetor If you experience any installation questions problems or issues please contact our technical service department between the hours of 8AM and 5PM CST M F 1 270 901 3346 DO NOT RETURN TO THE PLACE OF PURCHASE unless instructed to do so by technical service Recommended Parts and Accessories Part Number Description 1921 Street Demon calibration kit 1950 Idle kick up solenoid and bracket 1951 Street Demon TPS kit for use with electronic transmissions requiring a TPS signa
23. fuel into the venturii The Street Demon comes with a 028 discharge nozzle from the factory If more fuel is needed a larger discharge nozzle can be used If less fuel is needed a smaller discharge nozzle may be used Larger camshafts bigger cubic inch engines or Air Gap style manifolds may require a large squirter ad Accelerator Pump Nozzle Figure 17 To remove the accelerator pump nozzle use a 5 32 Allen wrench to remove the screw from the accelerator pump discharge nozzle Fig 17 Using a pair of needle nose pliers the discharge nozzle and screw can be removed from the choke tower area There are two gaskets used one under the screw head and the other under the discharge nozzle Use extreme caution so the gasket or nozzle is not dropped into the venturii Re assemble in the reverse order of removal Main Metering Tuning Theory of Operation Unlike a traditional Demon carburetor the Street Demon carburetor uses step up pistons and metering rods for enrichment The metering rods protrude through the primary metering jets restricting the amount of fuel flow available The metering rods have two steps that are used to restrict fuel flow under various driving conditions Manifold vacuum is routed to the step up piston and that vacuum works to overcome the step up spring pressure to hold the piston in the bottom of its bore Under a heavy engine load such as acceleration the engine needs more fuel to op
24. hrottle The step up piston is in the top of the bore and the rich step of the metering rod is in the jet Step Up Piston Step Up Piston Piston Spring Step Up Piston Spring Metering Rod Main Metering Jet Main Jet Figure 18 Figure 19 Tuning Tuning is best completed by using a wide band oxygen sensor to monitor air fuel ratios however tuning can be performed by reading spark plugs and taking vacuum readings Manifold vacuum will increase the closer you get to an ideal calibration it will fall off once you get past this point The ideal color for the spark plug porcelain is light brown or tan A color lighter than this indicates that the carburetor is lean a darker color indicates that the carburetor is rich There a few different areas that need to be looked at separately when it comes to tuning a Street Demon carburetor These areas are steady state cruise part throttle acceleration and wide open throttle NOTE Before making any tuning changes it is recommended that all test drives for steady state cruising and part throttle acceleration are completed before making any changes to the metering rods or jets WARNING Always take a helper with you to watch and record vacuum or AFR readings Never try to drive and write at the same time as it could result in an accident 12 Steady State Cruise Tuning Earlier the theory of how the main metering system works was explained During st
25. ir valve door too loose can cause the door to open a small amount at idle or low RPM cruising resulting in an undesirably rich condition Accelerator Pump Tuning and Adjustment When the throttle plates are in the closed curb idle position there should be no play in the accelerator pump connecting rod The pump lever should begin compressing the pump stem as soon as the linkage begins to move Incorrect adjustment of the pump arm linkage will delay the fuel discharge and the result is usually a stumble or hesitation as the butterfly begins to open 10 Bend here to set pump stroke 15 PUMP SETTING Figure 15 Figure 16 The accelerator pump stroke is set at the curb idle position to the dimensions show Fig 15 If you are experiencing a stumble or hesitation on initial acceleration it is possible that more or less fuel is needed for your particular application The connecting rod is positioned in the center hole 2 from the factory A faster discharge rate is possible if the connecting rod is relocated to hole 1 A slower discharge rate is possible using hole 3 This requires the rod to be adjusted to reset the pump stroke Fig 16 to the dimension shown in figure 15 If after adjusting the accelerator pump stroke a stumble or hesitation is still being experienced it may be necessary to change the accelerator pump nozzle Located under the choke flap the accelerator pump nozzle has two calibrated holes which discharge the
26. kage If running a Ford automatic and the kickdown linkage is needed a spring and perch kit Part 1954 is required NOTE Street Demon Carburetors will not work with a Ford AOD transmission 1 Press the screw retainer into position Fig 3 2 Remove shipping screw Fig 4 3 Install adjustment screw and locknut Fig 5 Consult the Ford Service Manual for proper setting 4 Install the mounting bracket and return spring Fig 6 pa 4 Figure 5 Figure 6 WARNING Install the transmission kickdown adjustment screw retainer adjustment screw and locknut as correctly indicated Failure to attend to this detail may result in a sticking wide open throttle or dangerous uncontrolled engine speed Chrysler Applications If installing on a Chrysler it may be necessary to purchase and install a Chrysler throttle stud part 124007 onto the Street Demon carburetor as in figure 7 below Throttle Stud Part 124007 f Figure 7 Vacuum Lines All Street Demon carburetors have four vacuum sources on the baseplate that can be used for PCV distributor vacuum diagnostics or any other vacuum operated accessories Fig 8 The large 3 8 vacuum port as well as the small 3 16 vacuum port located on the back of the baseplate is full below butterflies manifold vacuum There is also an optional 1 4 NPT provision if an additional full manifold vacuum source is needed The small
27. l 1952 GM throttle linkage cable attachment bracket 1953 Throttle cable and transmission kickdown bracket 1954 Ford kickdown spring and perch kit 160049 Universal carburetor installation kit 124007 Chrysler throttle stud 786004 Demon chrome 14 air cleaner assembly 1920 Street Demo rebuild kit Removal of Existing Carburetor 1 Remove the air cleaner exercising to carefully detach any vacuum lines from the air cleaner and marking them so they can be reassembled to the air cleaner in the same manner 2 Remove the existing carburetor by the following procedure A Carefully disconnect the fuel line WARNING Carefully protect the open end of the fuel lines so that no foreign particles can enter Wrap the end of the fuel line with a clean lint free cloth B Disconnect and mark all vacuum lines and wiring if any to the carburetor C Disconnect the PCV hose D Disconnect the choke rod or heat tubes if equipped 3 E Disconnect and remove the throttle linkage and automatic kickdown linkage Save all retaining clips F Unbolt and remove the carburetor from the manifold 3 If the intake manifold is being changed at this time install the new manifold according to the manifold manufacturer s directions Installation of Street Demon Carburetor 1 Install the carburetor mounting studs provided in the proper location on the intake manifold carburetor flange 2 Place anew carburetor flange gasket s
28. l Fuel Inlet Fittings Street Demon 9 16 24 threaded fuel inlet boss accepts the following optional fittings FITTING TYPE MANUFACTURER PART NUMBER SNIPER 60406421 BLUE 6 INLET BERFORMANCE 60406423 BLACK 6 MALE INLET BG FUEL SYSTEMS 142113 6 STANDARD EARL S 991942ERL If installation requires cutting the metal fuel line cut the fuel line with a good tube cutter This will minimize the chance of producing metal chip particles lf hacksaw must be used then metal chips must be removed WARNING During the fuel line installation DO NOT allow any foreign particles to enter the fuel lines which could then cause flooding and may result in a fire WARNING Keep the fuel line away from the EGR valve if equipped on the intake manifold WARNING In all cases where the fuel line has been cut it is essential that it be clean to ensure that no metal particles enter the fuel bowl after the new carburetor installation Remove the fuel line at the pump and blow the line clean with compressed air DO NOT use the procedure where the coil wire is disconnected the engine cranked for a few revolutions and the fuel collected in a container This procedure is unsafe because sparking can occur either at the coil or at the distributor end of the coil wire and ignite any fuel spilled in the engine compartment MAINTENANCE WARNING Fuel system components including fuel lines and the carburetor should be ins
29. n step and a 052 rich step During testing it is determined that during steady state cruising the engine is a little lean and during part throttle acceleration the engine is also a little lean A metering rod with a lean step of 058 and a rich step of 050 can be used to richen both of these areas up Remember from the theory of operation the steps in the metering rod go into the jet orifice essentially restricting fuel flow So to richen the mixture a smaller rod step is needed to allow more fuel to pass through the jet and to lean the mixture a larger rod step is needed to restrict the fuel passing through the jet If the desired result cannot be achieved by changing metering rods a larger or smaller jet can then be used to richen or lean the mixture in combination with the metering rods If during part throttle testing an issue such as a stumble or hesitation is encountered that goes away upon further throttle opening The engine may be experiencing a lean condition It may be possible to correct the lean condition by going to a stronger step up spring Step up springs are color coated and are rated by inches of vacuum of Hg The bigger the vacuum number the heavier the spring is For example a spring with a rating of 8 Hg means that it takes 8 inches of vacuum or more to keep the spring from raising the step up piston A spring with a rating of 3 Hg only takes inches of vacuum to keep it from raising the step up piston so it is
30. ne that is installed wrong If engine has been spitting back it seconds and then may have blown out the base gasket or a gasket in the carb dies 1 Slow flooding 1 Fix cause of flooding Engine staris OK 2 Step Up Piston up in bore piston and fix sticking issue or use a lighter but then gets real rough Lots of black 3 Venting system problem 3 Check entire venting system amp repair smoke 4 Fuel dripping from secondary 4 Tighten secondary air door 14 turn counterclockwise nozzles 1 Fast idle RPM incorrect too 1 Speed up the fast idle to factory specs slow Engine stalls when transmission is put 2 Engine running too lean 2 Check for vacuum leak Flow test carb to check jetting into gear because of vacuum leak or dirty jet 1 Vacuum leak 1 Check for vacuum leak amp repair 2 Ignition timing retarded too far 2 Reset timing 3 Accelerator pump nozzle has 3 Clean out the nozzle tip dirt in it Cold Engine Drivability 4 Accelerator pump cup swollen 4 Replace the pump cup Condition Hesitation stalling up from contact with bad gas or stumbling dead spot during acceleration Backfiring or spit back through carb chemicals 5 Secondary air door opening too quickly 5 Adjust air door 6 Vacuum hoses hooked up wrong 6 Connect up right Be especially careful of the EGR amp Dist connections 7 Distributor timing not advancing properly worn breaker plate worn shaf
31. ng the black choke cap controls the choke timing To rotate the choke cap loosen the three screws that secure the choke cap to the choke housing Fig 13 Rotating the choke cap clockwise will decrease the amount of time it takes the choke to open while counter clockwise will increase the time it takes This adjustment will depend on your climate and the vehicle it is installed on The factory setting can be referenced by making note of where the index mark is positioned in the cap in reference to the marks on the casting 9 3 The 14 Demon air cleaner Part 786004 is designed to clear the choke plate linkage on all Demon carburetors If you use another brand of air cleaner air cleaner gasket or air cleaner spacer it is necessary to make sure that the full range of motion of the choke shaft and butterfly are realized Failure to do so could result in the choke not operating properly This may cause an overly rich condition and or a high idle condition which could make the vehicle hard to control and stop CAUTION As with any modification inspection of the part after completion is a must Before use check the linkage for freeness of operation Your safety depends on it PERFORMANCE TUNING AND ADJUSTMENT Once you have completed the initial installation and preliminary adjustments you are now ready to test the vehicle and evaluate any other possible tuning adjustments Information on changing the configuration or fuel metering of your D
32. pected periodically to assure no fuel leakage and to ensure the soundness of the hoses Today s clean emissions engines provide higher temperatures in the engine compartment These high temperatures promote faster aging of non metallic materials Hoses that exhibit surface cracks when bent to 180 should be replaced The presence of liquid fuel demands tightening of fittings hose replacement and re torquing of the fuel system component flange nuts Connecting the Throttle Linkage NOTE Before connecting the linkage operate the throttle lever to assure the correct travel no sticking or binding by opening to wide open throttle and back to closed throttle several times Correct any sticking or binding conditions before proceeding NOTE If installing on a GM vehicle where the throttle cable needs to utilize the large hole in the top of the throttle lever a part 1952 GM throttle linkage cable attachment bracket will be needed With the pedal held firmly against a stop or the floorboard pull the carburetor to its wide open position Adjust the linkage rod or cable to the proper length and then attach it to the baseplate linkage Remember the pedal should make contact with a positive stop just as the carburetor gets to wide open throttle With the linkage rod or cable attached to the baseplate make sure the carburetor can return to its curb idle position Install your return spring s to the bottom of the throttle lever as shown in Figu
33. rance between the carburetor and the air cleaner Depending on the overall height obtain the proper length 1 4 x 20 stud supplied and install in the carburetor air horn and trim as necessary Close the hood slowly to ensure adequate clearance between the air cleaner stud and the hood If a longer stud is needed 14 20 All Thread can be found at most hardware or home improvement stores and may be cut to length WARNING Inadequate clearance between the air cleaner and the throttle lever could result in throttle sticking and uncontrolled engine speed Check the clearance between the throttle lever choke linkage and air cleaner for proper operation Check the clearance between the air cleaner and the hood before closing the hood completely Priming the Carburetor Mechanical Fuel Pump Crank engine for no more than 30 seconds and then pump the accelerator pedal twice Have an assistant observe to see that fuel is being discharged from accelerator pump nozzle when accelerator pedal is pumped If fuel does not discharge from accelerator nozzle wait 60 seconds and crank engine again Note Engine should not be cranked for more than 30 seconds at time to prevent possible damage to the starting system Always wait 60 seconds between each attempt to crank the engine Electric Fuel Pump On vehicles equipped with electric fuel pumps bump the pump switch on and off to fill the bowls a little at a time Avoid an abrupt surge of fuel into an empty carburetor
34. re 2 and check again for smooth operation to wide open throttle and then closed again TH350 _ Return Spring Hookup Point 200R4 700R4 4 Figure 2 Connecting the Transmission Linkage GM TH350 200R4 700R4 Attach the transmission kickdown stud supplied into the proper hole location on the throttle lever as seen in Fig 2 Attach the TV cable to the stud and adjust per transmission manufacturer s specifications using Chilton Motor or other repair manual designed for your specific transmission WARNING If you are unfamiliar with overdrive transmission TV cable adjustments consult a qualified transmission expert Failure to properly adjust the TV cable on overdrive transmissions can lead to poor shifting and or transmission failure Demon Carburetion assumes no responsibility for transmission damage or failure caused by improperly adjusted TV cables NOTE _ If this carburetor is to be used in an application utilizing an electronic transmission that requires throttle position sensor signal to operate properly Demon has you covered Part 1951 Street Demon TPS kit is designed to bolt directly to your new Street Demon carburetor to provide the needed TPS signal to an electronic transmission Consult the installation manual for the 1951 Street Demon TPS kit for installation and adjustment instructions Ford Kick Down Linkage All Street Demon Carburetors come with a Ford kick down lin
35. t pin hole in distributor diaphragm cracked hose etc 7 Check distributor and all related systems carefully Replace defective parts Warm Engine Drivability Condition Hesitation under light throttle dead spot amp stumble 1 Vacuum leak somewhere or hose off or hooked to wrong vacuum port 1 Inspect hoses Route and lead the hoses correctly Look for leaks caused by the wrong base gasket or if it was installed upside down 2 Accelerator pump problems 2 Inspect and adjust pump stroke pump plunger discharge nozzles and check valves Inspect the accelerator pump look for swollen pump cup 3 Float level set very low 3 Set float to factory specs 4 Ignition timing retarded 4 Set to factory specs Make sure advancing correctly 5 Idle speed set too fast amp mixture is too lean common 5 Richen up the idle mixture reset the idle speed to factory specs then reset the mixture using the lean drop method 6 EGR valve stuck on or coming on too early hose on wrong 6 Inspect hose routing to EGR valve amp inspect valve Replace as necessary Doggy runs rough lots of black smoke at idle 1 Choke staying closed or partly closed 1 Fix choke or heat source 2 Slow flooding 2 Fix cause of flooding 3 Step Up Piston up in bore 3 Remove step up piston and fix sticking issue or use a lighter step up spring 4 No power to choke
36. the idle speed to factory specs If it will not idle slowly the mixture is set too lean or there is a vacuum leak somewhere usually not in the carb 3 Fuel pump pressure too high 3 Check pressure Use a regulator to control the pressure or Gas pours out t don t high t when the engine is put on a new pump don t use high pressure type running 4 Gas is very gummy old or has 4 Clean bad gas out of carb Clean out of fuel system Use only too much alcohol or other good quality gas chemicals in it 5 Choke not working 5 Check cause of choke failure choke pull off failure or loss of power to the choke 6 Needle not seated properly 6 Try tapping the fuel inlet or needle amp seat area with the during initial fill handle of a screwdriver 1 Fast idle RPM incorrect too 1 Speed up the fast idle to factory specs slow Engine stalls when transmission is put 2 Engine running too lean 2 Check for vacuum leak Adjust idle fuel mixture Check for into gear because of vacuum leak or vacuum leak misadjusted idle fuel mixture 1 Vacuum leak 1 Check for vacuum leak amp fix it 2 Ignition timing retarded too far 2 Reset timing 3 Accelerator pump nozzle has 3 Clean out the nozzle tip dirt in it Hesitation During 4 Accelerator pump cup swollen 4 Replace the pump cup Acceleration Hesitation stalling stumbling flat spot or dead spot during acceleration Backfiring or spit back up thro
37. the metering rods are in the up rich position at idle If your engine has a radical camshaft check the manifold vacuum at idle if it is above 10 Hg the stock step up springs will work fine If the engine vacuum at idle is less than 8 10 Hg it will be necessary to change to a lighter or lower vacuum rated step up spring It may be necessary to try a couple different springs to determine which is best for your application Tuning for Elevation Street Demon carburetors are calibrated at sea level When going up in elevation the air is thinner and the carburetor may run rich As a general rule of thumb for every 2 000 ft in elevation the metering rod diameter should be increased 002 on the lean and rich steps Removal and Installation of Metering Rods Step Up Springs and Jets Metering Rod and Step Up Spring Replacement Loosen the step up piston cover screws Twist the step up piston cover plates to the side Fig 20 Remove the step up piston metering rod and spring FON gt Re assemble in reverse order of removal wt Step Up Piston A Jj amp Metering Roc Figure 20 Primary and Secondary Jet Replacement 1 Remove carburetor refer to removal of existing carburetor on page 4 2 Remove the metering rods and step up pistons as outlined in metering rod and step up spring replacement 3 Remove the two Phillips head screws from the top of the carburetor Fig 21 Figure 21
38. ugh carb up from contact with bad gas or chemicals 5 Vacuum hoses hooked up wrong 5 Connect up right Be especially careful of the EGR amp Dist connections 6 Distributor timing not advancing properly worn breaker plate worn shaft pin hole in diaphragm crack in hose etc 6 Check distributor and all related systems carefully Replace defective parts 7 Secondary air door adjusted too loose 7 Tighten air door turn counterclockwise 8 Incorrect accelerator pump nozzle 8 Install a larger accelerator pump nozzle 19 wot 1 Defective electric assist on 1 Replace it Hesitation Hesitation dead choke During spot or stalling that 2 Defective accelerator pump 2 Replace it Acceleration only seems to low output Cont occur after the first mile of warm up 3 Float level setting very low 3 Adjust to factory specs 1 Run a compression check 1 This will isolate bad rings or valves worn cylinder walls defective cylinder head or gaskets and excessive carbon Compression or deposits Misfirin 9 2 Check dwell variations 2 Check at variable speeds for excessive distributor shaft wear faulty For further questions please contact our technical department at 1 270 901 3346 Demon Carburetion Limited Warranty All Demon Carburetion Limited Warranties are extended to the original consumer only This Limited Warranty is not assignable or
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