Hesitating Holley

NOCOPO · #1 06-24-2002, 05:05 PM

Marlin, Just my 2 cents on hesitating holleys.(1) Power valve, make sure its not blown out. even the smallest backfire can ruin one. (2) The old fuel gyser out of the vent tube. If the float level is just the slightest bit high, when you jump on it, the fuel sloshes up and out down into the primaries giving you a hesitation. just my $.02 [img]/ubbthreads/images/icons/grin.gif[/img]

**YENKO DEUCE REGISTRY** · #2 06-24-2002, 07:49 PM

Thanks for the tips!! I purchased a pump cam kit and found a graph for their parameters, putting the orange one in Friday night. I found that the Pink one that was currently in there didn't activate the acc. pump until the throttle linkage moved almost a 1/4 in" [img]/ubbthreads/images/icons/shocked.gif[/img] It runs much better now, but still needs some more tweaking. I will have to try some of the others to find the one that works best.

I believe that this 780 Holley is too big for the LT1, especially with stock manifolds and smog system. We know for a fact that they run quicker in the 1/4 mile with the secondaries disconnected, (as do the '66 L79 Novas). GM put 780's on the solid lifter big blocks, and our theory goes that they just tossed one on the LT1 knowing that most would have headers installed anyway.

Pete, what did your dyno guy use on your 427/425 test from MCR? I thought he started with a 750 shop carb, and then went to ??

COPO PETE · #3 06-25-2002, 03:33 AM

Marlin. I am running the clear (no colour) cam with a 31 squirter. 72 primary and 82 back jets. And sorry, don't agree with you on the 780 being to big. You need it to run 106 mph through the traps! My car revs like a motor bike with the 780 on. On the 427, we stated with a 650. Way to small. Then we tried two different 780's on it. Oh ya, are you running a vent baffle on the metering block...that can help stop the stumble.
Peter

**YENKO DEUCE REGISTRY** · #4 06-25-2002, 01:09 PM

Thanks for the info Pete, will try the clear one next.
As for the 780, Neal and I accidentally disconnected his secondaries and he ran 102mph!! I plan on keeping my secondaries connected, putting a plugged power valve in there and bumping the jets up - - after I get the stumble ironed out.

When will we see the silver bullet again??

**YENKO DEUCE REGISTRY** · #5 07-01-2002, 01:37 PM

Hey Pete;
Tried the clear pump cam, good call!! This woke the car up a bit, still a little stumble left so I'm going to put in the jets that you suggested. Thanks for the advice [img]/ubbthreads/images/icons/smile.gif[/img]

**YENKO DEUCE REGISTRY** · #6 07-02-2002, 02:32 PM

Pete;
What's a vent baffle?
[img]/ubbthreads/images/icons/confused.gif[/img]

Chevy454 · #7 07-02-2002, 03:10 PM

Not to "interrupt" here, but what Pete is talking about is a brass(?) piece hangs on the 2 studs near the top of the metering block, and keeps fuel from exiting out the vent. I have one in my pocket (don't ask![img]/ubbthreads/images/icons/grin.gif[/img]), and I will try and nab a picture here in a second.

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