Where is your distributer vacuum connected to? I accidentally (read
stupidly) connected the vacuum advance to manifold vacuum rather than the
carb pre butterfly outlet. It killed the engine response like yours.
Have you checked your ignition timing at idle (about 8 degrees) then up to
3000 rpm to see what the advance is doing - should be about 30 deg total
advance or so?
My rule in troubleshooting - if it looks like a carb problem: check the
ignition system. If it looks like an ignition problem: check the carb.
Works 90% of the time.
You never said if you have a HEI distributer or points. If it's points
check
the gap.
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
--
Eugene Blanchard
http://www.catsasskustoms.com
Parts, Performance, Passion
News for Motorheads
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