350 SBC in 1963 impala HESITATION!?

Question

ok...i traded my holley 600cfm in on a brand new 750cfm carb :) it runs OK but not right, it has a little hesitation on slow acceleration and i can here a very faint sputtering sound when i mash it to the floor, it feels like if something was adjusted a little bit it was really hawl *** down the road, not sure what it is, was thinking my timing or spark advanced, i didn't adjust anything on the carb but the idle s***w, put a brand new fuel filter on, i have a 350 engine (supposed to of been rebuilt along with a 400 turbo tranny rebuilt) suppost to have a 292 or 294 cam in it, no headers (just the old type exhaust manifolds) mechanical fuel pump (looks used) vacuum type distributor, holley street dominator intake manifold... was just looking for some help before i take it to a speed shop and have then diagnose the issue, (saving money) i have replaced all the vacuum lines also (PCV and distributor)

Answer 1

My guess would be the carb too, I wouldn't adjust on anything if it was running ok before the carb swap.

Answer 2

belive it or not your Holley is too big for that engine. And espcially  with an automatic. You also probably have 3:23 gears on your differential and that is too high of a gear for the cfm on your carb. Another thing you can check is that the accleraton pump on your 750 is working right and squirting gas when you step on the gas.

Answer 3

it sounds like the acc. pump is a little out of adj. the squirt of gas is off.

if you call the edelbrock tec. line they can tell you how to tweak it.

good luck  

Answer 4

did you upgrade the intake manifold to handle the increase in air flow?

Answer 5

Couple of things...

1.  That mechanical pump may not be able to feed enough to a 750 cfm carb.

2.  You need to change over to an electronic ignition system (I'd recommend MSD performance ignition parts).

That's a place to start.  Adjust your timing before you do anything to make sure that the problem can't be solved easily.