hesitation from a stop


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By cbass139 - 16 Years Ago
I got and installed the MSD dizzy and man what a difference.  It starts right up with no problem and idles right around perfect.  I set the timing with the vacuum and idle with the vacuum advance disconnected and plugged.  When I took it for a drive it ran great with snappy accelleration, except from a start it hesitates just a little.  If I start out really slow and give it plenty of gas before starting up then I am fine but if I try to accelerate too quickly it bogs.  This would be fine but I am afraid that some day I will go to turn out on to a street and hesitate and put myself in a bad situation.  The carb has new accelerator pump that is gapped correctly, and a new power valve.  I pulled it into the garage and when I give it gas I can hear the air suck in when it hesitates.  Any ideas?  Oh it is a '58 f100 292 with a holley 2300, msd dizzy, flamethrower III coil, new plug wires and plugs.
By Ol'ford nut - 16 Years Ago
Where are you pulling your vacuum advance sorce from? If not the manifold give it a try.
By cbass139 - 16 Years Ago
No I am pulling it from the holley port and as I write this I realize that I never hooked it back up after tuning the timing and idle.  Will this make it hesitate from a start?
By Ted - 16 Years Ago
cbass139 (9/16/2009)
No I am pulling it from the holley port and as I write this I realize that I never hooked it back up after tuning the timing and idle.  Will this make it hesitate from a start?

Many of the Holley carbs come with multiple vacuum ports so you’ll have to sort out the ‘direct’ from the ‘ported’ hookups.  For carbureted vehicles, the use of 'ported' vacuum to the distributor was the norm from 1957 and on for all makes and manufacturers.  If the intial timing is properly set with the vacuum unhooked from the distributor, you’ll have no hesitation with a properly tuned engine.  Only on some of the emmissions vehicles was direct vacuum used and that was used in conjunction with temperature or other sensors to allow direct vaccum to the distributor only under controlled conditions.

 

If you’re setting the accelerator pump linkage with the throttle in the idle position, you’ll get a hesitation when attempting to accelerate from an idle.  With the throttle wide open, you’ll want ~0.015” freeplay before the diaphragm bottoms out.  If you have free play in the accel linkage in the idle position, you’ll likely have a hesitation when first giving the engine a quick blip of the throttle.

By cbass139 - 16 Years Ago
So, I was going to start working on the truck and systematicly go through the suggestions I got here, the ford-trucks.com guys, and a great carb site I found. One of them suggested starting by making sure I have the carb tuned correctly with max vacuum from the idle mixture at idle speed. So I did that and bam the problem was solved. So how I had the screws out different amounts, and by a lot. The one was set correctly but the other was like a full turn and a half to far out. I have no idea how I messed it up that much but it is fixed and man does it run nice. I can jam the gas any time I want and instant power. I used the timing suggested on Timmy's Y-block page (http://m571.com/yblock/index.htm) and I couldnt agree with him more on the tuning of the dizzy. I used his exact numbers and again the engine runs like a champ. Thanks all.