James Drinkwater wrote:
> Hi Guys,
> Got a Holley 650 double-pumper on "Dad's hotrod" with some probs
tuning.
> Upon depression of the throttle, my fuel/air ratio gauge shows that the
> mixture goes way lean and the engine goes into lean misfire and dropped
> power. Eventually it richens back up as the RPMs slowly increase. Not
> talking about the accelerator pump, just giving it a little more gas
while
> driving.
> Bought the carb from my machinist in the original box in like-new
> (visually) condition. Here's what's new and ruled out: high-volume fuel
> pump, fuel filter, fuel regulator and pressure gauge, float needles &
seats,
> jets (just to be sure), 6.5" power valve (like the original). both
> squirters appear to pump fine but the problem occurs when you slowly
roll
> into the throttle and it happens really quick (very throttle sensitive).
> It's a moderate, street performance SB Chevy that makes about 10.5"
vacuum
> at idle. I know the PV should move up to 8.5" but rolling into heavy
> acceleration (vacuum below PV opening point) doesn't overcome the lean
> condition either.
> Two last things are that idle mixture is pretty un-responsive to idle
> mixture screws, even when idle speed is as low as the engine will
reliably
> rev. Second, main jets were very, very rich at stock 67's (primary) and
> still a tad on the rich side with 65's.
> Dirty passage somewhere? Higher vacuum power valve needed and drill
the
> PVCR's? I'm a little stumped.
> Best Regards,
> Drink
>
> '87 TransAm (No computer controls)
> Holley 650cfm double-pumper
> Victor Jr. single plane
> 186 heads, fully ****ted with 2.02 valves
> 218/228 roller cam
> 1.6 magnum rockers
> 10:1 KB pistons
> Mallory Comp9000 distributor
> Hooker SuperComp headers
> 3.73 gears
>
>
Maybe you aren't talking about the accelerator pump, but you should be
looking at it.
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