350 Sputtering On Bottom End
Posted in Fuel Systems & Components | Asked on Apr 21, 2011
Below is the question about 350 Sputtering On Bottom End, I have 94 gm crate 350 in my 88 s10. I have put an edelbrock torker 2 intake and a lunati voodoo cam in it but other than that its completely stock. when i let it idle (800rpms) and then hit thegas it sputters alot. I can press gas slowly and it revs fine. I have put new hotter plugs in it check all of my super stock spark plug wires checked under the distrubutor cap (the distrubutor is a new accel dist) and everythings fine my timing is where it ought to be and my vacuum advance is working. I had a qaudrajet on it and i put a edelbrock 600 cfm on it to see if maybe it was the carburetor but it does the same thing? Please Please help? thank you!
It just started. I replaced the distrubutor a while back because the springs broke on my old one. The vacuum advance is running to a port on the carb and its advancing like its supposed to.
I also think its ignition related but yes i have removed the vacuum advance and it still sputters. ALSO it runs Great at high rpms it just that initial bump of the gas pedal that makes it skip and sputter.
There are 4 Answers for "350 Sputtering On Bottom End"
Check your PCV Valve. Had that same problem in a couple of Suburbans, new PCV Valve cleared it right up.
Has it always done this or did it just start? Like when you put the distributor in? Do you have the vacuum advance hose running to manifold vacuum, or to ported vacuum? If you have the vacuum line running to manifold vacuum, you are running advanced at idle, then losing the advance when you hit the gas, killing your timing. That alone could be the issue…..
Have you tried dis-connecting the vacuum line at the distributor to see if it still breaks up on accel? It certainly sounds ign related, since the carb swap changed nothing. A floating plate in the distributor would cause this issue. If it broke up at high rpm I would suggest coil. Or carbon tracking. But since it happens with initial accel, that is when the vac adv is applied to the dist……just a thought, at least…
Are you sure the carbs aer getting good fuel delivery? Every time I had a little dead spot like that it’s been that the timing was off just the littlest bit. A little to hot or to cold
Sounds like the leather plunger on the accelerator pump is worn, or the foot valve at the bottom is leaking. Also, float level is critical in these conversions.
Also, make sure you have fairly high, steady vacuum, as the intake manifold gaskets could be leaking causing this problem.
This sounds like an accelerator pump problem to me.
When the throttle plates are suddunly opened the manifold vacuum will go to near zero, this causes the atomized fuel to immediately condense on the interior of the intake manifold. this results in lean misfires and hesitation. make sure that the accelerator pump is working and if need be enlarge the acc. pump outlet port.