I'm replacing the head gaskets on my '99 Suburban. Seems one of them failed and was filling #6 with water when cold. My question is actually about the head gaskets themselves. I noticed that even though the heads and block all have large water passages the top passages through the head gasket were only 1/8" in diameter. This was particuarly alarming as the gasket was balloned in at the water passages as though water was trying to force it's way through way too small an opening. The new head gaskets are identical to the factory ones in regard to water passage hole size. Why are the head gasket holes so much smaller than the block and heads water passages? Can or should I drill the gasket water passage holes to match or even just a little bigger to allow more water through to the head?

 

The small holes are just there to let the air out of the block when you fill it with water, and steam out when youare running it.the reason they were ballooned is because the gasket was sandwiched between the block and the head everywhere but where the big hole is, thus making that shape. I've built so many SB Chevy enginesI cant even remember how many and have never had to drill out the head gaskets. with the exception of the 400 Ci SB Chevy where the cylinders are Siamese and these holes are not even in the same place as the ones your talking about. you should be good to go as long the block and heads are flat and clean

 

Thanks. That helps. Guess I'll go ahead and put it back together the way it is then.