Radiator Overflow Filling Up Under Boost

[cbird77]

My overflow tank fills all the way up when I run over 21 lbs of boost on a 1/4 mile pass. Tried re-torque on the heads....same. Car runs cool all the time. Has new radiator cap. On a pass temp gets up to 190. Has copper head gaskets and studs. Done a pressure test on cooling system with plugs out...held 15 psi for 2 hours. Compression check showed 140 to 150 lbs per cyl. #5 plug looked like it may have a slight green tint to it. Should I just pull the heads and inspect? Have heads pressure checked once they are off?

 

[Squid4life]

Try the GM seal tabs?

 

[earlbrown]

Gm seal tabs can't keep cylinder pressure from going into the cooling system.

Sounds like a basic set of leaky copper gaskets to me.

 

[Squid4life]

Don't know, never used them. Know a lot of guys swear they will seal up all kinds of sh@&!

 

[cbird77]

I used to run copper gaskets on my cast iron headed 351W, but the heads were o ringed. I don't know if these heads are oringed. Thinking bout going ahead and installing some cometic gaskets. Haven't tried seal tabs. Do the seal tabs work with antifreeze? Or water only? Guess I will pull heads and inspect first. May see something obvious.

 

[earlbrown]

Oh, they seal hell out of the 15PSI of coolant pressure... but don't stand a chance of holding in thousands of PSI of cylinder pressure.