Engine starts/idles fine for about 15 sec and then... - Pontiac GTO Forum
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post #1 of 3 (permalink) Old 04-05-2016, 04:56 PM Thread Starter
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SOLVED - Engine starts/idles fine for about 15 sec.

I hope someone can help me...I have a 467 Pontiac engine (71 455 engine with butler performance internals). When I start the engine, it'll run/idle for about 15 to 20 seconds fine and then run rough for a sec or two before cutting out. Here's the background...when I bought the car, it had a fuel regulator on it. After sitting for a few months during the winter, I removed the fuel regulator and tried starting the car. It ran for about 15 seconds before running rough and cutting out. I've cleaned the plugs, let it sit and started it again...same thing, it runs for about 15 seconds and then turns rough before cutting out. I can only keep it running if I keep my foot on the gas to keep the RPM's up. Now I've tried it with the fuel regulator connected and it does the same with or without the fuel regulator. I've tried new spark plugs gapped at .040-.045 (what the gap was on the original plugs), same thing. The latest attempt was gapping the plugs at .060 which seem to have it run a few more seconds before turning rough and cutting out (maybe it just seemed longer). When the fuel regulator was connected, it was running at 5 psi, but of course I forgot to check the fuel pressure (under hood) today without the fuel regulator...I'm guessing it's higher. Here are the details...

-Holley 830 Classic HP Carburetor
-NGK-R5674-6 spark plugs (currently gapped to .60)
-MSD Digital 6AL system

UPDATE: I installed the Fragola PTFE 6-AN hose, fuel pump and fuel sending unit. After reviewing a lot of videos on YouTube, I set the Holley carb fuel levels (they were a little high) and idle mixture screws. Finally got it running again. Eventually I'll get it to a shop that can double check the tuning, etc...but for now it's good to go.

Last edited by aeconfidential; 04-24-2016 at 03:11 AM.
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post #2 of 3 (permalink) Old 04-06-2016, 07:54 AM
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Sounds like it might be flooding out (bad needle and seat?). I'd remove the air cleaner and look down the inside of the carb while it's running to see if it's getting too much fuel.
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post #3 of 3 (permalink) Old 04-06-2016, 10:15 AM
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5/16" fuel line.... sounds like chassis is an early base engine Tempest or LeMans. With near 50 year old steel fuel line, how old are rubber hoses back by the tank and leading into fuel pump? The last decade's ethanol laced junk gas destroys old rubber hoses and old stock fuel pumps. Not a Holley guy, but would pull float bowls and ck needle and seat for rubber debris.

With what ought to be a strong engine under the hood, will second, its well past time to get a 3/8 fuel line routed and clipped onto the frame. Depending on chassis, a preformed line can be swapped on with only loosening body bushings on passenger side and removing bolts on drivers side and carefully lifting up drivers side of body a few inches.
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance

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