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post #1 of 8 (permalink) Old 07-09-2010, 12:20 PM Thread Starter
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1972 Vette hard starting

I have recently purchased a 72 vette with a 350 engine. (Not original). After driving it in the hot weather it is sometimes hard to start after sitting for a few minutes. I will have to crank it for 5 to 10 seconds and floor it to get it to start. I have tuned it up with plugs, wires cap rotor, etc. It always starts fine when cold. Any ideas out there? has anyone else experienced this problem?
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post #2 of 8 (permalink) Old 07-09-2010, 12:34 PM
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It's somewhat normal for a hot engine to take alittle bit longer to start than a cold engine. When hot the fuel will vaporize at a faster rate below the carb in the intake manifold. 5-10 seconds is a bit long though. If you could tell us whether the engine is all stock or if the carb and intake have been changed that would help in giving better suggestions.

Mine takes 3-5 seconds to start after driving for 10 miles or more then stopping to go into a store for a few. Usually a shot or two of fuel and it fires up but not instantly. I have changed alot of things from stock so that contributes to my starting.

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post #3 of 8 (permalink) Old 07-09-2010, 12:38 PM
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Quote:
Originally Posted by backriverman View Post
I have recently purchased a 72 vette with a 350 engine. (Not original). After driving it in the hot weather it is sometimes hard to start after sitting for a few minutes. I will have to crank it for 5 to 10 seconds and floor it to get it to start. I have tuned it up with plugs, wires cap rotor, etc. It always starts fine when cold. Any ideas out there? has anyone else experienced this problem?
If flooring it helps, it sounds like your choke is sticking partly closed and holding it to the floor opens the choke the whole way so that could just be all that is wrong . What kind of gas mileage are you getting ? You need to check that first, then proceed to other areas.
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post #4 of 8 (permalink) Old 07-09-2010, 02:00 PM
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Quote:
Originally Posted by backriverman View Post
I have recently purchased a 72 vette with a 350 engine. (Not original). After driving it in the hot weather it is sometimes hard to start after sitting for a few minutes. I will have to crank it for 5 to 10 seconds and floor it to get it to start. I have tuned it up with plugs, wires cap rotor, etc. It always starts fine when cold. Any ideas out there? has anyone else experienced this problem?

I assume you have a Quadrajet carburetor? The Quadrajet's have two "well plugs" in the bottom of the float bowl. They are aluminum plugs that are pressed in then crimped. Often these well plugs leak and the contents of your float bowl will drain into your intake manifold; leaving your float bowl completely empty and fouling your rear spark plugs. There are two fixes. One is to put a rubber "gasket" under the plugs (usually included in a carburetor rebuild kit), and the other fix is to remove them and seal them with JB-Weld or other epoxy. As it is a permanent fix, I prefer to use the epoxy method. To remove them, drill them in the center then use a dent puller to pluck them out. Then once they're out, you can fill in the drilled hole with epoxy. It sounds like your float bowl IS getting drained and causing your slow starting as it takes several seconds worth of cranking to re-fill your float bowl.

Last edited by toobroketoretire; 07-09-2010 at 02:03 PM.
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post #5 of 8 (permalink) Old 07-09-2010, 02:58 PM
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It sounds like a flooding issue, if it a Holley , your float levels may be to high,or you make have a boiling issue when you shut down..it may require an insulator between carb and manifold
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post #6 of 8 (permalink) Old 07-09-2010, 07:30 PM
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Originally Posted by fishslayer143@yahoo.com View Post
It sounds like a flooding issue, if it a Holley , your float levels may be to high,or you make have a boiling issue when you shut down..it may require an insulator between carb and manifold

Rochester Quadrajets are well known for boiling over in the summer months because their fuel bowl is so small and their zinc body retains so much heat. A real thick mounting gasket helps to keep them cooler. Just be sure to only snug them down and NOT over tighten them.
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post #7 of 8 (permalink) Old 07-10-2010, 11:48 AM
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I agree with Toobroke and Fishslayer, sounds like the fuel is expaning under heat and flooding, check the float levels, thicker gasket and DO NOT over tighten if they are Rochesters. Mine came with a rebuilt Qaud and the old one, both of which had been over tightened which I realised after many hours of adjusting and rebuilding to try and make them run. It warps the base and turns them into junk. Put on a new Holley and run perfect ever since.
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post #8 of 8 (permalink) Old 07-11-2010, 07:36 AM
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Quote:
Originally Posted by toobroketoretire View Post
I assume you have a Quadrajet carburetor? The Quadrajet's have two "well plugs" in the bottom of the float bowl. They are aluminum plugs that are pressed in then crimped. Often these well plugs leak and the contents of your float bowl will drain into your intake manifold; leaving your float bowl completely empty and fouling your rear spark plugs. There are two fixes. One is to put a rubber "gasket" under the plugs (usually included in a carburetor rebuild kit), and the other fix is to remove them and seal them with JB-Weld or other epoxy. As it is a permanent fix, I prefer to use the epoxy method. To remove them, drill them in the center then use a dent puller to pluck them out. Then once they're out, you can fill in the drilled hole with epoxy. It sounds like your float bowl IS getting drained and causing your slow starting as it takes several seconds worth of cranking to re-fill your float bowl.
Yes I agree this is a common problem w/ the Q-jet. You may also get an occasional miss or rough idle as the fuel drips off the well plugs and gets sucked into the intake manifold. I've seen kits that replace the lead plugs by drilling and tapping the passageway and inserting a small allen head set screw and then epoxy in place.

Did it many times with about a 50% success rate.
Holley , yes Holley will rebuild a Q-jet carb for you and repair this fuel well plug problem also.
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