[Goatracer1]

I can remember back in the 1950's guys over boring some of the old V8's 1/8 inch over. What is the max that a 1964 or 1962 389 could be over bored if it was strictly a street engine?

[25stevem]

I took a 65 389 out .090" over ( .060" over 400 ) and had no issues on the street, but I think that now looking back I got lucky in terms of core shift which I new nothing about 46 years ago!

I would not go more then .030" to .040" especially if you might be some day handing this motor down to someone who might need/ want to rebuild it again.

[Goatracer1]

Am I wrong, a .060 400 would be almost .120 over 389?

[b-man]

Originally Posted by Goatracer1

Am I wrong, a .060 400 would be almost .120 over 389?

You’re not wrong.

A 1962 block might be a candidate for that overbore, a 1964 I wouldn’t think so although that was supposedly the last year for thickwall block castings.

[PONTIAC LARRY]

i thinks its just 59 389 maybe 60 model can go .125 over

[hurryinhoosier62]

Originally Posted by PONTIAC LARRY

i thinks its just 59 389 maybe 60 model can go .125 over

Definitely. The ‘59 and ‘60 389s had some of the thickest cylinder walls of all the 3” main blocks. Bruce Wilkie and I once had a conversation about over boring a ‘59 389 block .125. Bruce said he had done it but his machinist recommended using Hard Block afterwards.

[25stevem]

Yup!
I am sure that since it was only making like 370 hp and never topping 5800 that it did not seem to be a issue.

[78w72]

i was concerned about going .060 on a 481988 400 block, spoke to butler about it when ordering the stroker kit & was told that he & beswick used to bore 389 & even some early 400s .90-.100 over with no issues related to the overbore, these were heavily raced engines. he said guys did this all the time before sonic checking was available. its a good idea to check that now when going to a bigger overbore, but guys did this for decades before that service was available.... used stock rods/cranks to pretty high rpms too.

[Goatracer1]

I reason that I ask is because I have a new set of 400cid 0.060 over pistons and both a 1962 389 and a 1964 389. I was wondering if I could use the pistons and one of the blocks. The engine would go into a 1962 Bonneville that will be strictly a cruiser.

[racegto65]

Originally Posted by Goatracer1

I reason that I ask is because I have a new set of 400cid 0.060 over pistons and both a 1962 389 and a 1964 389. I was wondering if I could use the pistons and one of the blocks. The engine would go into a 1962 Bonneville that will be strictly a cruiser.

I've got a 1965 389 block currently .090 over that has been street driven and bracket raced since it was built in 2007 with no issues. And no I didn't sonic check this one.

[geeteeohguy]

Originally Posted by Goatracer1

I reason that I ask is because I have a new set of 400cid 0.060 over pistons and both a 1962 389 and a 1964 389. I was wondering if I could use the pistons and one of the blocks. The engine would go into a 1962 Bonneville that will be strictly a cruiser.

You would be soooo much further ahead of the game by trading/selling the oversized 400 pistons instead of hogging out a decent block to very thin dimensions that will never be usable for an additional rebuild unless it is sleeved.

Seriously. Have a set of dished .020 or .030 over pistons made and run your cruiser for decades to come on pump gas with no worries.

[Goatracer1]

I don’t have decades for me to run so it would be the next owner’s problem. I know people don’t like buying second hand engine parts so I figured it would be easier for me to use them.