Hard starting after the car is at operating temperature - Page 2 - Pontiac GTO Forum
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post #11 of 14 (permalink) Old 10-26-2019, 08:18 PM
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Also, with a '67, there is a one-year-only heat passage in the intake under the carb for quicker warm-up. The factory installed a stainless steel plate under the carb gasket to block raw exhaust from boiling the underside of the carb. Many of these plates have gone missing over the years. Mine was when I got it. The plate is MANDATORY with a '67. I used two base gaskets and installed the plate in between like a sandwich. No more percolation or flooding. And I live where it's HOT. On my '61 Corvette, I had to make Masonite spacer plates to install under both carbs to insulate them from engine heat. It solved 90% of my percolation problems. Today's gas is formulated for fuel injected engines, not carburetors, and boils off very easily.
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post #12 of 14 (permalink) Old 10-31-2019, 05:37 AM
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Originally Posted by integrity6987 View Post
When I read this - I interpreted as similar to a hot start issue I have.

So to clarify - is the engine cranking rate the same when cold has hot?

If the heat from the engine transfers to the starter wiring and starter motor - this dramatically increases the resistance in the circuit causing slower cranking. On very hot days (~90) and driving for ~25 mins, mine will not crank at all for ~15mins. I have to pop the hood and wait it out.
A little off topic but I wanted to share that I had the same issue. I installed larger battery cables and a Powermaster mini starter and it solved my problem.
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post #13 of 14 (permalink) Old 10-31-2019, 10:03 AM
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I had similar issues with my Buick 350 at one point. I added a carb spacer to keep the carb from getting too hot and boiling out the gas that was in the carb. Additionally I wrapped the fuel lines with an insulator to keep the fuel in the lines from also getting too hot.

Another thing that could help with the issue of vapor lock ( if that is actually what is happening ) would be to add an electronic fuel pump. If your fuel is boiling out of the carb when it sits this means your fuel pump has to pump gas back up to the carb. Adding an electric fuel pump would ensure your carb is getting fuel before you turn the key. Just my .02 Cents

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post #14 of 14 (permalink) Old 11-07-2019, 10:19 AM
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It’s a carburetor. They do that. Hot start procedure from the owners manual probably says to slightly depress the accelerator. Hold it open until the engine clears it’s throat. DON’T pump the pedal.
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