You might have seen my posts under Engine re Holley secondary power valve plug, but now I just want to get the #%*& thing running right before this weekend for the Goodguys show.
350, seems like a moderate build (but internals unknown). Holley 4150, List 9379, 750 CFM. Sits on a Holley intake manifold. Yes, it's over-carbed, so I just want to make it run as good as it can.
Engine was running real rich at idle and under power. I rebuilt the carb and noticed that it had size 70 jets - stock is 68. I now have the following jets: 64, 66, 68 and 70 to play with.
When I got it back together, I first adjusted the float levels, then the idle mixture screws (vs the idle speed and vaccume). Then I tried several different primary jet sizes (currently at 66) and adjusted the timing to where it seemed to be best (20)
The engine now backfires out the carb just off-idle when I goose it. Screwing in the idle/mixture screws INCREASES the idle speed and vaccume. It seems like it likes 1/2 turn out from bottom. 68 jets don't make a difference.
So none of this makes sense to me. Unless I didn't adjust the float levels correctly. Just how much fuel should be coming out of the check hole? I set it so there was only a VERY faint drip, which in hindsight could have just been caused by vibration of the motor and thus be way too low.
So I'll adjust them up to higher levels tonight. IF that doesn't work, what else should I try to adjust?
[ 03-25-2004, 05:12 PM: Message edited by: Luke68ss ]
'68 SS<br />350, Holley<br />4 sp M21 <br />12 bolt posi<br /><br />My first 'real' muscle car