Is Vapor Lock Normal With Holley Carb?

[JIm Datsko]

Having owned 5 previous Mid Year Small Block Coupes, I've accumulated over 100,000 miles driving the fantastic Sting Ray coast to coast, on Route 66 etc, over the past 30 years. But I'm always learning something new about them. Especially since purchasing my current 1967 327/300 Sting Ray; of which the adventure of driving it home were detailed in the two "Sting Ray Adventure" articles recently published in The Corvette Restorer.

Most of my miles were driving with the Carter AFB Carb equipped 1965 Sport Coupe, which made for a sweet running engine.

Since owning 1966 and 1967 Sting Rays, it seems like I've had nothing but Holley Carburerator Problems. And understand why many people say the best thing is to replace them with a bolt-in Edelbrock carb.

The biggest problem seems to be vaporlock, as when the engine coolant temp reaches 200-210 degrees [ the fan clutch is now in the process of being restored or replaced ], the engine will barely run, has no power even at nearly full throttle, and eventually dies. I replaced the used Holley Carb, with a brand new one, and the problem continues as before; even though it's installed using factory style installation re: gasket, metal fuel line routing, etc. My Carter AFB never had this problem regardless of engine temperature. Is it normal to expect vapor lock or fuel boiling with the Holley once the coolant temp exceeds 200 degrees. I'm surprised if that's the case, because the new cars all run at about that temperature.

Though I have an aftermarket copper or brass radiator, it keeps the coolant at the 160 degree thermostat temp as long as the car is moving at all. Even when I crossed the Mojave Desert and Mountains in 100 plus degree temps.

Anyone with expertise in this vapor lock area?

Thanks,
Jim
E-mail: JRDatsko@aol.com
Tel. (231) 264-0041

[Stephen L.]

Re: Is Vapor Lock Normal With Holley Carb?

Did you check your heat riser for operation? I have a 67 427/390 w/3811 holley and have not experienced your problem. Do you have to let the car cool down to get it re-fired? Do you have the stainless steel insert as well as the gasket between the carb and the manifold?

[JIm Datsko]

Re: Is Vapor Lock Normal With Holley Carb?

I should have mentioned that I removed the heat riser during engine overhaul, since I rarely drive the car during winter anyway. Removing that restriction helps the car to breath better.

Yes, it does have both the SS and the rubber gasket under the carb.

Once the car and presumably the fuel in the carb have cooled down it starts again and runs fine until the fuel gets hot again.

Thanks,
Jim D.

[Rich Puleo]

Re: Is Vapor Lock Normal With Holley Carb?

The only time I've seem vaporlock problems was when the fuel lines were routed too close to heat sources. I've seen poor octane & contaminated fuel cause similar problems, also clogging filters, colapsed fuel socks & hoses, & weak pumps. You may want to check your float level, that it's not too low. Biggest problems I've seen with a Holley is getting them to adjust right. They get tempermental & uncooperative & sometimes it could take a while. I don't live in a hot climate, someone may say differently.

[G B.]

A different perspective

Jim -

I don't consider vapor lock to be a carburetor related problem. You may have a perculation problem with your Holley, however. This happens when the fuel boils in the bowl and overflows into the venturis. There is nothing I can think of inside any carburetor to "lock" from vaporized gasoline.

The term vapor lock implies a fuel line or pump problem. If the gas on the upstream side of the fuel pump vaporizes, it won't be pumped to the carburetor. Mechanical fuel pumps can only transfer liquid gas.

If you do have a vapor lock problem, I believe it is probably between the gas tank and the fuel pump. I haven't seen this occur on a mid-year Corvette (or any other car) since the fifties. I guess it could happen if you have an exhaust leak near the fuel line though.