389 Pontiac?

ss wannabee · 02-09-2013, 07:23 PM

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

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

Quote:

Originally Posted by Hudlow66

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

Yup! Ive had that happen to me before, too

Dwight Southerland · 02-10-2013, 08:51 AM

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

Quote:

Originally Posted by Dwight Southerland

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!

02-09-2013, 07:23 PM	#1
ss wannabee Senior Member Join Date: Jun 2005 Posts: 663 Likes: 0 Liked 7 Times in 7 Posts	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.)

02-09-2013, 10:58 PM	#2
Hudlow66 Junior Member Join Date: Apr 2011 Location: Spokane Valley, WA Posts: 59 Likes: 0 Liked 1 Time in 1 Post	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. __________________ Phil Hudlow 6678 (S/C, S/G, ET-PRO)

02-09-2013, 11:24 PM	#4
Hudlow66 Junior Member Join Date: Apr 2011 Location: Spokane Valley, WA Posts: 59 Likes: 0 Liked 1 Time in 1 Post	Re: 389 Pontiac? Yup! Ive had that happen to me before, too __________________ Phil Hudlow 6678 (S/C, S/G, ET-PRO)

02-10-2013, 08:51 AM	#5
Dwight Southerland VIP Member Join Date: Dec 2001 Location: Arkansas - In the middle of everything. Posts: 2,001 Likes: 64 Liked 780 Times in 194 Posts	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?