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ss wannabee 02-09-2013 07:23 PM
389 Pontiac?
 
How far can you safely bore a 389 block? Also turn down the crank?

1965 vintage...and for the street. (Asking for a friend.)

Hudlow66 02-09-2013 10:58 PM
Re: 389 Pontiac?
 
Ive gone to std. 400 bore before. Then again, I just got done boring one to .040 and ran into water in one of the cylinders. Best to have your machinist sonic test it. That way there's no suprises.

Paul Precht 02-09-2013 11:20 PM
Re: 389 Pontiac?
 
Quote:
Originally Posted by Hudlow66 (Post 368517)
Ive gone to std. 400 bore before. Then again, I just got done boring one to .040 and ran into water in one of the cylinders. Best to have your machinist sonic test it. That way there's no suprises.
Back in the mid 70s, I was boring a Chev 350 block .020" for a SS build after a few hours of deburing and one cylinder opened up into a large air pocket. The block was scrapped.

Hudlow66 02-09-2013 11:24 PM
Re: 389 Pontiac?
 
Yup! Ive had that happen to me before, too

Dwight Southerland 02-10-2013 08:51 AM
Re: 389 Pontiac?
 
I have a couple of similar stories and it has always left me scratching my head. How did an engine survive 80k miles being driven every day for years with a cylinder wall that was less than .050" thick?

Jeff Lee 02-10-2013 11:53 AM
Re: 389 Pontiac?
 
Quote:
Originally Posted by Dwight Southerland (Post 368538)
I have a couple of similar stories and it has always left me scratching my head. How did an engine survive 80k miles being driven every day for years with a cylinder wall that was less than .050" thick?
And the opposite; how can I have a passenger car 390 AMC engine and the factory TSM's of the day said "Do not overbore more than .022" and I'm at +.070" over?
Different day, different mold at the foundry I guess. That or the factory had a huge supply of +.022" pistons they needed to unload!


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