SB 400 Heads

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May 2, 2009 | 11:01 AM

Fscott

Thread Starter

Instructor

Joined: Jun 2005

Posts: 156

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From: Liverpool NY

SB 400 Heads

Is it mandatory to drill the steam holes on my 350 heads that I'm putting on a 400 block? I'm getting mixed information on this. The guy who is building the short block says he had the same setup and didnt drill his and is confident I wont have any problems. I know this isnt a big process (seemingly) but I broke a bit off while doing it and I would prefer to leave them as is if I can.
Thanks

May 2, 2009 | 11:05 AM

MotorHead

Race Director

Joined: Apr 2000

Posts: 17,676

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From: Who says "Nothing is impossible" ? I've been doing nothing for years.

I would not build 400ci based motor that had steam holes in the block without having the steam holes drilled in the heads

May 2, 2009 | 11:23 AM

gerry72

Safety Car

Joined: Aug 2000

Posts: 3,711

Likes: 43

From: San Antonio TX

A factory 400 block has to have the holes in the block and the head. If you don't you'll have low-rpm cooling problems. Not much of an issue for engines that spend their life over 3k rpm, but under that, you'll have problems. Has to do with the way the water jacket is cast between the bores. Aftermarket blocks do not have this problem because they use a different jacket design.

May 2, 2009 | 11:01 PM

Fscott

Thread Starter

Instructor

Joined: Jun 2005

Posts: 156

Likes: 0

From: Liverpool NY

Thanks guys.
I'm gonna take the heads down and have the holes drilled. No sense messing around with this.

May 2, 2009 | 11:34 PM

73, Dark Blue 454

Melting Slicks

Joined: Mar 2005

Posts: 2,838

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From: Austin TX

If the engineers at GM thought they were needed on Granny's 75 Caprice, you can bet they're sure needed once you start adding compression and HP (which means more heat).