Stumble off idle -

[blykins]

Originally Posted by Grubby

No need to change carbs. I have put almost 8,000 miles on this car - most with the Holley 750. I drive it down to about 40 degrees. The cold did not have this much impact on the other carb for the last 3 years.

Reconfirmed no vac leaks. I used the propane torch method along the intake gaskets, carb base and carb fuel bowl gaskets. A leak on the inside of the intake is possible but i doubt it.

Quickfuel tech support suggested going down a few sizes on both IAB and HSAB. After reading up on the air bleeds; my guess is the IAB is the most likely. Decreasing the size of the IAB will richen the mixture at the high RPM range of the idle circuit (up to 2500rpm) and raise the RPM the carb transitions to main metering. The worst lean surge is between 1600 and 2000rpms in 5th gear.

I am inclined to drop IAB next. How many sizes? How many different sizes should I order and in what ranges? I assume the IAB change should be made to the primary side of the carb only. At least initially. Quickfuel tech says it is likely that with this change I will need to go down a few sizes in main metering jets.

I have been reading everything I can find to get up to speed on Holley 4150 tuning. I am feeling more comfortable.

I missed Brent today. So I will catch up with him or his carb builder later.

John

John, do you have different contact info that I can use? I tried returning your phone call just a few minutes later yesterday and couldn't get an answer or a voice-mail. I also sent two emails without a response.

I guess I mis-read, or couldn't remember, but I thought your problem was on tip-in at a higher cruising speed. 1600 is pretty low.

I would give Scott a call today. I told him that I would probably put you in touch with him. I imagine that he will tell you to do some air bleed swaps as the carb is probably a little lean everywhere with the temp changes outside. It's about 38° right now.....a little different than several weeks ago when I sent you the carb.

Let me know how I can help, but I'd say you're not too far away from getting it nailed.