I have a 389 ('66 GTO) that needs cylinder boring to clean it up, but it is at .060 over already. Can I safely go bigger? Will I need custom made (expensive) pistons for this?

Thanks
Ken

I have a 389 ('66 GTO) that needs cylinder boring to clean it up, but it is at .060 over already. Can I safely go bigger? Will I need custom made (expensive) pistons for this?

Thanks
Ken

I'd look for a new block, It sometimes runs hot at .060, I wouldn't want to go bigger,

http://kurtspontiac.homestead.com/Pre1964Pontiacs.html

4.0625 + 0.060 = 4.1225
Maybe you could use custom 4.125 pistons. At least it's a common ring size.

http://fiedlerh.home.att.net/

Are all 389's alike? I can get my hands on a 65 Catalina with a 389.

Theres very little difference in a 65 and 66 389 block

http://kurtspontiac.homestead.com/Pre1964Pontiacs.html

If it a matching no 389 for your GTO don't throw it away. Get it sonic tested and check the cylinder wall thickness.I have gone .90 on 400 blocks with no problems.You probably could use a .40 or .60 over 400 piston and be ok.

wanna race? gimmie the move--

Since I'm working with '66 GTO heads, and '66 everything else for that matter, are '65 and '66 389 blocks the only years I can use? Or is any 389 block useable? Does it matter if it came out of a GTO , Catalina or something else?

Thanks
Ken

The '64 GTO and GP have a compatible 389 block (starter mounts to block), the other '64 389s and earlier 389s won't work in your '66 GTO. Any of the '65 and '66 389 blocks will work.

Let's go racing!
www.outlawpontiacs.com/members/B-Man2.php
www.outlawpontiacs.com/members/B-Man.php

When looking at a core block, what do I look for to tell if is is set up to have the starter mount to the block?

At back of the block on the drivers side,outside
the back lip of the oilpan there should be 2 holes tapped.That's where the starter bolts up.

Eric