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Old 06-26-2008, 03:43 PM
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Originally Posted by Curtis Thornton
I am getting different feed back from folks about whether of not I should drill the steam holes in the new heads I just purchased. I bought a set if heads from Jegs (world sportsman). I have spoke to a friend of mine whom has built several small block chevy 400 and he stated that he has never drilled the steam holes out on his 400's and it they have never ran hot.

Are there any pros out there on sb chevy 400 that can give me some insight before I put this thing together
They don't run hot where you can see it, that is the engine temp doesn't increase where the temp gauge sender is.

What happens without the 400 drill is that coolant can't escape from the top of the closed area where the siamesed cylinder bores meet the deck. This coolant turns to steam which is a poor conductor of heat. The local area at the top of the bore overheats and distorts. The likely outcome is cylinder wall and deck cracking in this area, especially around the normally hot running center cylinders on each side and or head gasket failure in this zone.

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