Adjusting Holley Carb on 440 Engine with cam

[Paul Cotton]

I have a 440 CI engine with a Bullet cam, Edlebrock Performer intake and a Holley 4150 750 vacuum secondaries and electric choke carb. The motor fires right up on starting, but idles pretty rough until it warms up. Once it warms up everything is fine until I drive it. The car is an automatic with a Cheetah shift kit in it. If you get on the car a few times, after you let off the gas pedal the engine wants to die. Any suggestions what could cause this?

 

[Shorthorse]

Float adjustment?

 

[NOSTRT980]

does the choke work correctly and do you have the correct power valve?

 

[Xp29h]

Yeah, check floats make sure fuel level is right at bottom of opening. Then check air idle screws on each metering block. Use a vacuum gauge. This will really help on those.

Here's an article on adjusting vacuum secondaries
http://www.racingjunk.com/news/2015/04/21/tuning-a-vacuum-secondary-of-a-holley-carb/

Here's article for air idle adjustments
https://forums.holley.com/entry.php?429-How-To-Adjust-The-Idle-Mixture-On-Holley-Carbs

Good luck

 

[PurpleBeeper]

These guys are on the right track. ASSUMING not vacuum leaks, I'd guess timing & carburetor adjustment issues are your problem.

1. Rough idle at startup, but idles fine when warmed up
a. Sounds like your choke isn't working - check with air cleaner off
b. "could" be carburetor idle fuel mixture adjustment.
c. do you get any puffs of black smoke out of the tail pipes at idle?
d. What's your initial & total timing set at?
e. what do your plugs look like? black? white? tan? half-melted?

2. Wants to die after getting on it a few times
a. could be carburetor floats set too low
b. could be plugged up fuel filter
c. could be debris "sometimes" plugging needle/seat or it's sticking a little bit
d. could be fuel pump can't keep up - do you have a fuel pressure gage?

 

[dvw]

More info needed. What size cam. What size converter? How many turns is the speed screw turned in from the throttle plates closed? How many turns are the idle screws out?. How much RPM drop in gear?
Doug