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 ported 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
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