Boiling Gas
Thread Starter
Melting Slicks
Joined: Oct 2005
Posts: 2,114
Likes: 0
From: upstate N.Y.
Boiling Gas
After taking the 76 for a ride after a restore within a quarter mile it hesitated alitle while going about 20mph. and then ran allright for 3 miles and died. I thought ,out of gas. Got gas and on the way home ,it died again. Took off air cleaner and gas in the carb was boiling. Is this a float sticking problem or over heating. Didnt blow any water out overflow.After sitting it started back up and ran fine. I am afaid to drive it too far from home till I figure this out. Any thoughts guys. THanx in advnce.
Drifting
Joined: Oct 2004
Posts: 1,496
Likes: 1
From: Lafayette Louisiana
I think its referred to as vapor lock. You may need a thicker carb gasket, heat shield or spacer to insulate the carb from the engine heat. I have never experienced it while driving but have had trouble restarting one after it sat for just a few minutes. Holley sells a heat shield or you can make it yourself.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
The vapor lock usually occures at the fuel pump.The pump gets an air lock and it cant pump air very well.This causes the engine to stop.Is your return line hooked up?
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
No-the return will help with that not happening.Is your heat riser stuck?How old is the gas?Could it be winter gas with fuel line freeze additive.How thick is the carb gasket?Did it do this before the restore?
Last edited by ...Roger...; Aug 16, 2007 at 11:25 PM.
Thread Starter
Melting Slicks
Joined: Oct 2005
Posts: 2,114
Likes: 0
From: upstate N.Y.
No heat riser. Fresh gas.The carb gasket is the stock one that came with rebuild kit. Ran well before this happened. after it stalled you could look down the carb and see the gas boiling. the motor wasn't overheating and turned over normally.just wouldn't start up until it cooled down.
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Thread Starter
Melting Slicks
Joined: Oct 2005
Posts: 2,114
Likes: 0
From: upstate N.Y.
When looking in carb I could see it actualy like boiling.After thinking about it i wonder if it isn't water that was boiling. seems like the gas would have evap. The shop where i had the paint done put 3 gal. of gas in it.Maybe had water in it. A quater mi. down the road from my house it sputtered and then was allright for 3mi.Put dry gas in maybe it will work. Just worried if it was gas about having a fire.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Dale - Check this thread and see if your gasket looks like Pauls under his carb.Dry gas will also make fuel boil sooner.Can you show us a pic of your setup?
http://forums.corvetteforum.com/show...t=boiling+fuel
http://forums.corvetteforum.com/show...t=boiling+fuel
Le Mans Master
Joined: Jul 1999
Posts: 9,206
Likes: 17
From: Sewell NJ
You didn't mention what type of carb it is. If its the stock Q-Jet you should have it mounted to the manifold with an insulating gasket. This was stock on most Q-jets and cured the problem of gas boiling. If its an aftermarket carb you can get an insulating gasket for those also. My Edelbrock came with a divided insulating gasket and I've had no problem with gas boiling. Here's a pic of the thick carb gasket for 74 to 81 Q-Jets. You can see the torque limiters around the bolt holes. This prevents you from overtightening the gasket.These run around $8~$10.
Drifting
Joined: Jul 2006
Posts: 1,871
Likes: 6
From: Sault Ste. Marie Ontario
I brought this up a few weeks ago. I've got a buddy with a 454 Chevelle doing the same thing.
The culprit was the intake gaskets. He did not install the metal port reducers over the exhaust cross-over ports. These ports allow hot gases to run under the carb to actuate the choke and improve warm up in cold weather. He's running an electric choke now and only runs the car in the summer months so he changed the gaskets and the problem is solved.
I made the same mistake with mine and have installed a set of gaskets that completely close the openings. Hopefully I won't have that probelm when my car hits the road.
The culprit was the intake gaskets. He did not install the metal port reducers over the exhaust cross-over ports. These ports allow hot gases to run under the carb to actuate the choke and improve warm up in cold weather. He's running an electric choke now and only runs the car in the summer months so he changed the gaskets and the problem is solved.
I made the same mistake with mine and have installed a set of gaskets that completely close the openings. Hopefully I won't have that probelm when my car hits the road.
Instructor
Joined: Nov 2004
Posts: 189
Likes: 0
From: Somerville NJ
On my 74 in hot weather it would smoke after sitting for a while when the engin was hot. I blocked off the exhaust crossovers in the intake man. it is now good. I thought it may have been boiling. 
Thread Starter
Melting Slicks
Joined: Oct 2005
Posts: 2,114
Likes: 0
From: upstate N.Y.
Thanx A Bunch Guys. That Gasket Is The Same That I Have .it Boiled For About 5 Minutes Or More . Would Gas Do That Or Would That Be Water?it Is A Q-jet With Edelbrock Intake. Never Had This Problem Before.
Drifting
Joined: Jul 2006
Posts: 1,871
Likes: 6
From: Sault Ste. Marie Ontario
I suspect it's gas. My buddies carb was so hot he could not hold his hand on it.
Thread Starter
Melting Slicks
Joined: Oct 2005
Posts: 2,114
Likes: 0
From: upstate N.Y.
Just an update.Put 2 bottles of dry gas in a full tank and drove for about 45 minutes with no problem.Hope thats the end of the problem. Only thing i can figure is the shop where i had the body work done put gas in it that had water.Keeping my fingers crossed.Thanks for all the input guys......Dale
