Builder

A friend has an SBC with a blown head gasket at 9k miles. I told him to take the heads and get them checked to see if they are warped. What would be an acceptable amount of surface variation? I am guessing 0.003", but would like to hear from those with experience.

Also, what can cause a blown head gasket (besides bad torque, a broken bolt, and overheating)? A compression test showed 175 psi. Valves, piston, and cylinders show no visual sign of damage. The gasket on the opposite side shows signs of break-down in exactly the same place.

Who make the best gaskets for an SBC?

Thanks,

johnjzjz

fel pro gasket is the best all around and have machine shop take .010 cut off head and if it cleans up stick it back on no other mods required jz

Builder

Thanks, John. I will pass that along. Do the heads need to be stripped of valves for the milling?

johnjzjz

if you dont want the chips in the cylinders the real small ones

Builder

Having the valves lapped, too.

Craig@ETPerformance

iTrader: (1)

You will need to have the heads taken apart, you might create more issues down the road. Having the valves lapped is not a bad idea, just to see how everything looks. make sure the block is flat in those spots where the gasket looks bad. A clean up cut should all that is needed which is around .003 to .005. I would just check everything, it might be just installed wrong or not torqued right.

Builder

Thanks Craig. I will pass that along. I don't think he's pulling the engine, though.

I advised cutting a few thou of the top to be the best route. Basically, I said a complete rebuild would be the right thing to do since the engine needs to come apart...may as well let the machine shop work their magic.