434ci smallblock steamholes?? - Team Camaro Tech
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post #1 of 4 (permalink) Old Mar 23rd, 01, 03:53 AM Thread Starter
Join Date: Mar 2001
Location: UK
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You know when building a street 400ci chevy from a street block you should drill 6 steam holes in the heads to match those on the block..???

Well, what are you supposed to do with a Bow-Tie 400ci-type block ??(GM10051184) (where there are no steam holes in the block between siamesed bores anyway ..)
I guess the block was designed to be travelling at speeds above 3500rpm all the time so you always had enough circulation to avoid needing these holes..Should I drill holes in the block & the heads using a gasket as a template..??
Help..!!??? - (I am building a 434ci smallblock motor - mostly street performance use.....)
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post #2 of 4 (permalink) Old Mar 23rd, 01, 03:44 PM
Join Date: Apr 2000
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I would, Ed. You might want to drill 1/16" holes instead of the 1/8" and 3/16" holes that are stock (I think). That way you will have max deck strength and still bleed the steam out. But do drill the heads w/ stock holes. That way they will still line up. IMHO! pdq67

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post #3 of 4 (permalink) Old Mar 25th, 01, 01:52 AM
Join Date: Nov 2000
Location: Chandler AZ USA
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I run a 400 in circle track aplication, I always drill and tap them. A 434 is hard on blocks, the plugs help stiffen the web son you don't get the hair line cracks that are common from the steam holes
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post #4 of 4 (permalink) Old Mar 25th, 01, 05:12 AM
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Join Date: Jan 2000
Location: Wilton, Ca. USA
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I'd also check with the head manufacturer you're going to use. Edelbrock on their Victor Jr. heads only wants the bottom three holes drilled in the heads; they say to leave the top three blocked. I've used them on two different 406's with no heating issues.

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