351 windsor question

SPRBLKXX · #1 (**permalink**) 10-15-2009, 03:58 PM

i have a cobra 351 windsor and have a issue when heavy accel starts popping then takes off hard, ive rebuilt carb, test msd dist, replaced coil, adjusted valves, ck timing, holley carb been gone thru. what else help.

blykins · #2 (**permalink**) 10-15-2009, 04:26 PM

What are you calling popping?

What was your initial/total time set at?

bobcowan · #3 (**permalink**) 10-15-2009, 05:59 PM

You need to check fuel pressure under acceleration. That can be tough to do without a dyno, though.

If you can buy/borrow a LM-1 or something similar, you can see what the AFR is doing when it's popping. I'd bet that's well above 14:1.

Gaz64 · #4 (**permalink**) 10-15-2009, 09:53 PM

Quote:

Originally Posted by SPRBLKXX

i have a cobra 351 windsor and have a issue when heavy accel starts popping then takes off hard, ive rebuilt carb, test msd dist, replaced coil, adjusted valves, ck timing, holley carb been gone thru. what else help.

Some more info about the engine would be helpful, compression, cam timing etc and what carb you're running.

"carb been gone through"? Was it running ok before?

Continous popping? or backfire through the intake on hard acceleration?

Either way the engine's not liking the momentary incorrect A/F ratio, accelerator pump volume correct and duration too long or short (pump nozzle) or volume incorrect (pump cam).

Double pumper, vac sec?

Rick Parker · #5 (**permalink**) 10-15-2009, 10:20 PM

Quote:

Either way the engine's not liking the momentary incorrect A/F ratio, accelerator pump volume correct and duration too long or short (pump nozzle) or volume incorrect (pump cam).

Gary is on the money, check the accelerator pump circuit.

blykins · #6 (**permalink**) 10-16-2009, 05:30 AM

He needs to clarify what kind of popping it is....could be a lot of different things, including detonation if he's hammering it under a load at a very low rpm.

SPRBLKXX · #7 (**permalink**) 10-16-2009, 05:41 AM

The car is a kit car, 200 miles on it. Friends car, Engine is a summit 351w with a holley carb ,I ll get size soon. Under normal driving its fine but under heavy accel it starts popping (like its clearing it throat) then it takes off, breaks tires loose type take off. when you get towards the end of that gear starts again. fuel pressure is 6-7 lbs.

Clois Harlan · #8 (**permalink**) 10-16-2009, 10:55 AM

Sounds like you have a bad accelorator pump on your carb or you are loading up. First check your fuel bowl levels and make sure you are not getting to much gas in your carb.