2004 Impala 3.4L

[AllGM]

New to this site. NEED HELP!
I'm replacing head gaskets. When I took the heads off I saw erosion on the deck of the block. I took the short block to a mechanic to look at it. He said he decked the block .006". Now as I put it back together I see the pistons at TDC are above the block deck about .025". He said the engine is designed that way and the pistons are suppose to rise above the deck. Are the pistons on this engine suppose to protrude ABOVE the deck of the block?

[neophile_17]

Yes, but I don't know if .025" is too much. If memory serves the head gasket is .060" thick when compressed leaving you .035" of clearance. .035" is the old school recommended minimum FWIW. Hopefully some one with experience on this platform will chime in. Good luck!

[Guest]

Yes, in stock form the 3400 pistons come proud of the deck by .020", so your mechanic (who I hope is also a machinist), did deck the block close to what he said he did.

[AllGM]

Thank you very much for responding. Now I know.