vapor lock on a 1969 300 hp

[Mark Niksic]

My 69 vapor locks when hot. I believe it had a plastic spacer under the factory carb originally, but is not currently there. It also has a Holly bolt on replacement carb instead of the factory carb. On my 65 I plugged the manifold heat holes but do not see a way to do it on this car. Should I install the spacer.Any suggestions would be greatly appreciated, Mark.

[Joe L.]

Re: vapor lock on a 1969 300 hp

Mark-----

No black plastic spacer was originally used for your application. There was originally an asbestos-type gasket, GM #3884574, and a stainless steel heat baffle, GM #3884576. The heat baffle is used on TOP of the gasket.

The carb heat groove in the front of the manifold carb flange can be plugged in exactly the same way as you did the 65 manifold. I HIGHLY recommend doing it and eliminating the carb pre-heat.

[Jim T.]

Re: vapor lock on a 1969 300 hp

Mark if your car still has the original intake are you using the Holley 6210 spreadbore carb? I have been using this carb on my 68 327/350 since 1974. I use the gasket on the intake first then the stainless steel block off gasket to prevent crossover exhaust from directly contacting the carb just like the original factory installation. I have never had any vapor lock problems.

[Mark Niksic]

Re: vapor lock on a 1969 300 hp

Thanks for the input! My car does use the 6210 spread bore. I will review gasket/heat shield installation. I will also look again at plugging those holes.