Hesitation problem.

[Dibly74]

Just wondering what causes the car to hesitate and stumble if I slam the gas from idle. Restristed exhaust due to cats being clogged from running rich for a couple thousand miles? Misadjusted carbureator?

[hrmwrm]

many things, but quite often it's from a lean condition. is this only at startup or anytime? from startup, improperly set choke. anytime, vacuum leak, accelerator pump going, bad carb. i am assuming this is a carbed engine. could also be late timing.

[Dibly74]

Well I just set the timing correctly a couple of weeks ago. And it does it anytime but especially when its cold. About one year ago the carb was rebuilt according to specs. Also when I coast down from speed, letting my foot off the accelerator, it does a small pop pop pop from the exhaust like a small backfire. Thats whats leading me to think about clogged cats maybe.

[pro-five-oh]

I'd check all the adjustments on the carb first, the fuel (sticky accelerator pump?) sounds like the problem.

[gadget73]

sounds like your accelerator pump isn't working properly. A backfire out the carb is normally a lean condition. Entirely possible the pump shot needs to be increased.

[hrmwrm]

clogged cats show up more with power loss at rpm. did this happen also before you set the timing? if not, i would guess late timing might be a factor. if you're sure about the timing, then it is a lean condition.

[Dibly74]

Yeh, it did this before the timing. I actually was the first person to touch the timing on the car, which was off by two degrees. The pop pop pop sound is comming from the exhaust I think. Im pretty sure the pump is working good because it gives a nice shot when I push it. I guess its probally a lean condition then. I haven't driven another one to know if its loosing power at higher RPMs. Thanks for the suggestion and I will try to adjust it this comming weekend when im off.

[hrmwrm]

also search and be sure there are no vacuum leaks. they are usually responsible for a lean condition. (intake gaskets, vacuum lines, carb gasket, open ports at the carb, open pcv, badly worn throttle shafts/bores, loose intake bolts, etc)

[Steve Moran]

Often times Ford products of that era have a problem with the Power Valve blowing out when the engine backfires through the carburetor.
when that happens they exhibit the same problems you describe
They have came up with a blowout resistant valve that is put in most carb kits now days, If you do rebuild yours you should ask if your kit comes with one.

[Dibly74]

My rebuild kit did come with a new one. I didn't ask if it was blowout resistant or not. It was a Tomco kit.

[Steve Moran]

My rebuild kit did come with a new one. I didn't ask if it was blowout resistant or not. It was a Tomco kit.

Tomco should have one in it, they are a good carb kit company and IIRC they and Holly where one of the first to do it