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Another hard starter with a gas smell

sunger

Well-known member
Joined
Jan 14, 2007
Messages
57
Location
Southern California
Corvette
1968 427 convertable
I have a 68 427/400, and have a problem with starting and a gas smell also. It starts easily (fires in about 1 second) when the car sits overnight, but it is slow starting when I restart after driving for a while. If I restart right away, like stopping for gas, it fires right up. If I let it set for 10 minutes plus, it takes about 5 seconds of cranking to fire. I also get some backfires through the carb. occasionally as soon as it starts. Not frequently, but just now and then. I have tried pumping the gas heavily, not at all, and just a few times, but no change.
I also get a strong gas smell when I shut it down, but I can not find any gas leaks. I doubt the center carb is draining because it starts quickly when cold.
I would appreciate any thoughts.
And yes, it does have tri-power.
Thanks
Steve
 

minifridge1138

Well-known member
Joined
Feb 2, 2007
Messages
908
Location
USA
Corvette
1982 Black Fastback
you may have 2 separate issues.
The only time i've ever had mine backfire through the carb was when my timing was off (way off).
But I don't think that timing would cause the starting problems you're describing.
Still, i'd check my timing and make sure that it is set correctly.
 

MikeMc71

Well-known member
Joined
Apr 30, 2007
Messages
100
Location
Tucson, Arizona
Corvette
1970 Roadster, 1971 LT-1, 1971 Coupe
I have had a similar problem in the past. I believe mine was also a combination of problems. Timing slightly off, choke adjusted a little too rich, and HEAT. Being in So Cal, you probably have the same heat issues we dio here in AZ. On very hot days, I believe the gas vaporizes in the carb, just from the heat off the intake, when you try and start it, way too much vapor gets to the cumbustion chamber, and it acts like its flooded. As far as the backfiring, I would first look at the timing, lookk for a vacuum leak, and have a compression test done. I have a '75 I am rebuilding, and one of the valves sticks, and causes fire through the carb.
 

minifridge1138

Well-known member
Joined
Feb 2, 2007
Messages
908
Location
USA
Corvette
1982 Black Fastback
Carb Backfire:
The only cause I know of (and there may be more that I am unfamiliar with) is that the spark is firing when the intake valve is open. When the intake valve is open, the exhaust valve is colsed, so if it fires at this point, the exhaust has no place to go except back into the intake manifold and out the carb.

Personally, I would start by setting the engine timing. It is easier than adjusting idle mixes or checking valves.

After you KNOW that timing is not the problem, you can start looking for other problems.

Good luck!
 

sunger

Well-known member
Joined
Jan 14, 2007
Messages
57
Location
Southern California
Corvette
1968 427 convertable
I will check the timing, but do you think it will wander due to how long it has been parked?
Thanks for the help
steve
 

jims427400

Well-known member
Joined
Jun 7, 2005
Messages
763
Location
Temperance Michigan
Corvette
67 427 tripower,68 427 tripower,04 Z16, 62 340hp
Just cureous, are you still running a tripower setup. If so, are you sure your secondary linkages are set up properly and not closing off when your rpm's are low.
 

Tepot

Well-known member
Joined
Sep 13, 2005
Messages
307
Location
Moncton, NB, Canada
Corvette
1974 Metalic Blue L-48 Coupe 4 speed
Mine did the exact same thing recently. I don't have a Quadra jet carb no more. I'm using an Edelbrock performer 600cfm. But Quadra jet's would give same problem. Timing is good. idle mixture screw are set ok. The problem was the floats on the carb. they were not properly adjusted. So when the gaz got warmer. The gas would get dumped into the carb and would flood the engine. so would take me alot of cranking to start the car and would backfire and smell gaz like crazy. And always when go on a drive to the store and letting it sit for 10 minutes. Have someone check the floats in your carburator. could need adjustment or they could leak.

good luck
 

minifridge1138

Well-known member
Joined
Feb 2, 2007
Messages
908
Location
USA
Corvette
1982 Black Fastback
just sitting will not effect timing.
The only way for your timing to be off is:
1) slipped chain (gear is worn or chain stretched)
2) distributor moved. (this can happen if it isn't bolted down tight enough or if the clamp is bad. My cousin has a 1968 Camaro RS and his distributor slips no matter how tight you have the bolt. He just needs to replace the clamp)

Again, i'd make sure timing is right before you look for anything else because using a timing light is so easy. MUCH easier than adjusting carb settings.
 

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