Holley 750 Hesitation
Thread Starter
Safety Car
Joined: Nov 2004
Posts: 4,359
Likes: 57
From: Mundelein Illinois
Holley 750 Hesitation
Ok Guys,
I changed the jets to 78 and I increased accel pump from standard to 35. The hesitation is a little better but still there. Just for reference Holley part number 80508S with electric choke on a GM 385 fast burn with Hot Cam. I think Iam going to die from exhaust fumes.
Timing is 16 degrees at idle and 36 degrees at 2800RPM. Dist is shimmed per lars.
I did see accelerator pump cams, anybody try these. Holley part number 20-12
Any ideas
I changed the jets to 78 and I increased accel pump from standard to 35. The hesitation is a little better but still there. Just for reference Holley part number 80508S with electric choke on a GM 385 fast burn with Hot Cam. I think Iam going to die from exhaust fumes.
Timing is 16 degrees at idle and 36 degrees at 2800RPM. Dist is shimmed per lars.
I did see accelerator pump cams, anybody try these. Holley part number 20-12
Any ideas
Last edited by spedaleden; Dec 3, 2006 at 12:25 AM.
Pro
Joined: Jun 2004
Posts: 700
Likes: 0
From: Lantana TX
Originally Posted by spedaleden
Ok Guys,
I changed the jets to 78 and I increased accel pump from standard to 35. The hesitation is a little better but still there. Just for reference Holley part number 80508S with electric choke on a GM 385 fast burn with Hot Cam. I think Iam going to die from exhaust fumes.
Timing is 16 degrees at idle and 36 degrees at 2800RPM. Dist is shimmed per lars.
I did see accelerator pump cams, anybody try these. Holley part number 20-12
Any ideas
I changed the jets to 78 and I increased accel pump from standard to 35. The hesitation is a little better but still there. Just for reference Holley part number 80508S with electric choke on a GM 385 fast burn with Hot Cam. I think Iam going to die from exhaust fumes.
Timing is 16 degrees at idle and 36 degrees at 2800RPM. Dist is shimmed per lars.
I did see accelerator pump cams, anybody try these. Holley part number 20-12
Any ideas
Drifting
Joined: Jan 2006
Posts: 1,944
Likes: 22
From: Yooperville MI
Describe exactly where the hesitation occurs, ie: off idle, light acceleration, WOT. Trying different pump cams should be the last effort after the hesitation is gone.
1. If the 35 shooter helped, maybe you need a 37.
2. If the fumes are that bad, you might be too rich at idle so smaller primary jet size might be needed.
3. What is your vacuum at idle and what power valve are you using?
4. If the hesitation is going into WOT, maybe you need to try different secondary diaphram springs.
5. Is the secondary shaft free to move or is it binding? Sometimes if you overtighten the carb mounting the base can distort and cause the shaft to bind. Especially with certain spacers or multiple gaskets.
To famailiarize yourself with Holley's, pick up a copy of the "Holley Carburetor Handbook" for Selection Tuning and Repair of 4150 & 4160 carbs. It is the Holley bible, about 80 pages. If you study it carefully, you'll have a better understanding of how and why all the parts and adjustments work together the way they do.
1. If the 35 shooter helped, maybe you need a 37.
2. If the fumes are that bad, you might be too rich at idle so smaller primary jet size might be needed.
3. What is your vacuum at idle and what power valve are you using?
4. If the hesitation is going into WOT, maybe you need to try different secondary diaphram springs.
5. Is the secondary shaft free to move or is it binding? Sometimes if you overtighten the carb mounting the base can distort and cause the shaft to bind. Especially with certain spacers or multiple gaskets.
To famailiarize yourself with Holley's, pick up a copy of the "Holley Carburetor Handbook" for Selection Tuning and Repair of 4150 & 4160 carbs. It is the Holley bible, about 80 pages. If you study it carefully, you'll have a better understanding of how and why all the parts and adjustments work together the way they do.
Pro
Joined: Jun 2004
Posts: 700
Likes: 0
From: Lantana TX
Originally Posted by gdh
what is your a/f ratio?
Since this is all about AFR you might want to spend a few buck on a meter. Your AFR today and what it will be in the middle of the summer will be different and make your car run different. If you do decide to do this make sure and by a wideband O2 version.
