my primary throtle blades when closed are open about 1/8'' is that to much?car runs rich at idle just going by smell and it will burn your eyes if you squat behind the exhaust.runs going going down the road and dosn't fall on it's face when you get on it even from idle. by the way it's a 750 dp 69 and73 jets and the power valve cheks good and is a 6.
holley q?
- Thread starter dartbob
- Start date
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A 750 double pumper is a pretty big carb for most small blocks. It may be too big for a 383 unless you've got compression and a big cam. Holleys are noted for the metering block gaskets shrinking and drying up after the carb sets for a while. Is it a fresh carb or a swap meet find? It may need a overhaul. Have you adjusted the idle mixture? They are the little screws on the side of the metering block (the 1" thick blocks between the float bowls and the main body). A tune-up tech would have a tach and a vacuum gauge but you can help it by ear. Slowly screw one screw in no more than a half turn at a time. Listen to the
engine . If it starts to smooth out turn it in another 1/2 turn. adjust side to side until it runs its best. The adjustments may make it idle too high which you can adjust by loostening the idle speed screw( near the throttle cable). If the engine runs worse or doesn't respond to adjustments it needs rebuilt. If you have a stock 273 or 318 a 600 or 650 is plenty. Bigger engine and more modifications/ bigger carb. An engine usually runs better with a smaller carb jetted up yhan a large carb jetted down. Hope this helps! Toolmanmike
engine . If it starts to smooth out turn it in another 1/2 turn. adjust side to side until it runs its best. The adjustments may make it idle too high which you can adjust by loostening the idle speed screw( near the throttle cable). If the engine runs worse or doesn't respond to adjustments it needs rebuilt. If you have a stock 273 or 318 a 600 or 650 is plenty. Bigger engine and more modifications/ bigger carb. An engine usually runs better with a smaller carb jetted up yhan a large carb jetted down. Hope this helps! Toolmanmike
dusterdon
Well-Known Member
My guess is that this motor doesn't have a stock cam. You need to turn the idle screw in to much. It is idling on the main circuit. There are 2 ways around this. My favorite is to take the carb off and turn it over. in the baseplate on the secondary side you'll see a set screw that controls the opening for the secondaries. Take a small screwdriver and turn this in around 1 turn. It will be very stiff. You'll probably need to put a wrench or something on the screwdriver to help turn it. Put the carb back on and fire it up. It will probably idle rather fast. Now you can close the primary butterflies with the idle screw. This works the same as drilling holes in the secondary butterflies, but much easier and not permanent. If you need more adjustment go ahead, but don;t go more than 1/2 turn at a time. This has always worked for me.
don
don
moper
Well-Known Member
dusterdon said:
what Don said. 1/8" means you're not on the idle circuit anymore. Also, make sure your timing is set where you want it, maybe want to add some initial to help the idle characteristics, then crack open (very lightly like Don said) the secondaries with the set screw. Then slow it down and readjust the mixture screws.
thks guys i guess i chould have added more on the motor.it's a magnum head la 360 with 9.8 comp.292 comp extreme hy.cam tti headers.air gap intake.it made 400hp on the dyno and the jets where tuned there.on yeah tq.was 425lbs. motor run goods just fouling plugs.i'll check out that ajustment on the secondarys.and see how that goes.also changing coils if you read my msd post.hope it all helps i'm tired of cleaning plugs.good new is my buddy who runs a race engine shop just put in a chaiss dyno.10 mins from me. life is good sometime.
BJR Racing
Well-Known Member
Holleys are known for being rich from the factory, make sure that the air bleed holes in the top of the carb aren't blocked as it doesn't take much to block these. If they are blocked by dirt or what ever the carb will run rich no doubt about it. I generally open these up a bit and it leans the carb out when small jets dont do the job.
BJR Racing
BJR Racing
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