Max bore on 389?
 

What is the max bore on a 66WS 389. What does it cost to resleeve one?

What bore size are you at now?
Core shift could leave 7 of the 8 cylinders good to go .060” over ( which I have done without hard block) and that 8th one even if you offset bore could still be to thin on the thrust side.

Some 65-66 389 blocks were thin wall castings and will not tolerate more than .030 over bores, some of them will tolerate .060 over bores. There is no way to know which is which. My advice would be to sonic test the block before committing to what your block will tolerate.

In 1972 I bought a 65 GTO that was bored .060 and the cylinder wall collapsed. I ended up with the TRW piston in the water jacket, and a completely destroyed engine, so I speak from experience. A $1200 mistake in 1972 money. After The demise I read in a car enthusiast magazine that 65-66 blocks were changed from the 64 heavier cast blocks and were called "thin wall castings" by Pontiac, and that they were only safe for a .030 over bore. That is what is known as being, a day late, and a dollar short with the pertinent information. As far as cost of sleeving a block. it all depends upon what portion of the country the shop is in doing the operation.

If you could find a low mileage 67-76 400 block with standard bores, they are already .060 oversize from a 389, no overbore required, but to keep the valve reliefs at the proper angle and position as the 389 heads, you need 389 + .060 pistons. You can bolt 389 heads to a 400 block with the 400 pistons, but the valve lift has to be limited to .450 so that the valves and pistons have no interference because of incorrect positioned valve reliefs on the 400 pistons for a 389 head.

:2cents:

Hopefully this information helps you with your choices.

With a sonic test completed, a .060 overbore would be the maximum. Just no way to know if core shift will spoil those plans. As old as these blocks are getting now, many have thin walls from erosion on the inside of the water jackets in addition to core shift. Installing 8 sleeves in an old 389 block is a non-starter as far as cost. The only exception would be the desire to retain a numbers matching drivetrain in an extremely rare model IMO. Around here in Southern, OH to have 8 sleeves installed, then square decked, and plate hone would run $2200.00-2500.00 for parts and labor including the sleeves. Once finished, you still have a block that is inferior to a STD bore 389 IMO. Even installed correctly, the new sleeves tend to move around and get out of shape as they heat cycle the first 50-100 cycles.

About a year ago we put 8 sleeves in a 1964 hemi block. That was about the cost I listed above. It came out OK. Was going into a factory lightweight trailer queen car so they just needed it to run, not leak and be reliable for car show duty.

I would add that with the availability of custom pistons these days that you are not locked into going even .030”. You may be able to do less.

I have zero knowledge on the max bore... but when I was building my .060 481988 400 stroker I asked Butler Sr on a phone call if .060 was a concern on these early 70's 400 blocks, he chuckled and said 99% of the time its not a concern, he didnt get into core shift or sonic testing, just said usually not a problem at this power level of ~500hp.

He then went on to say how back in the day before strokers were available he, Arnie B & others used to bore mid 60s 389 blocks to .090 & .100 with no real issues, and that was for hard racing use... no hard block or sonic testing, just pushing the limits of what those blocks could do.

One needs to consider the intended use of the block. A fellow that worked for me bored out his Olds 400 to 455 bore size. It left the bores dangerously thin. Yet it took 23k hard miles before the cylinder cracked and hundreds of dragstrip passes. This engine was making around four hundred horsepower. At seven hundred it wouldn't of lasted nearly as long.

I'll be the guy in left field.
For a "just get it running" build we took the original 66 WT 389 to +.090. Loaded it with SpeedPro forged pistons, King bearings, a Lunati Voodoo Roller Cam, Cloyes billet timing set, KRE 74cc heads, Melling oil pump, fuel injection, Canton pan, etc.
Intended as a "Temporary" engine, we now have nearly 30k miles on it. Primarily used for long distance touring.
Temp stays around 190* on a hot TX summer day, may creep to 212* in traffic with the AC on.
Goal is build a MR-1A to 433 with a 4.00 stroke, yes it will have to have custom sleeves.... one can dream...

Good info, thanks for posting.

All-Pontiac offers smaller bore sizes. We use them for Super Stock builds.

Anyone that is skeptical about the 65-66 blocks not having as much material as the earlier 389 engines. There is documented proof that the 65-66 blocks are possibly inferior in the amount of iron used in those castings compared to earlier castings. Having had one .060 over bore fail due to weak cylinder walls I would at the very least sonic test any of these blocks before boring one more than .030 oversize. Since there are other options for stronger castings, 65-66 would be my last candidate for a .060 overbore without a sonic test.

If you consider boring one .060 without testing it, I'll default to Clint Eastwood. famous line in the movie Dirty Harry :D

I've done the same thing. We had a 66' 389 block and some .060 400 pistons. Had it sonic checked and it was good to bore. I was really surprised!

I personally know of two ‘66 389 blocks that had .090 cylinder walls from the factory due to core shift. I own a ‘64 “big car” 389 and a ‘59 389. Of the two, I lean heavily toward the ‘59 389 after several long discussions with Bruce Wilkie several years ago. A ‘59 389 weighs substantially more than a ‘65/‘66 389.

Well, I know the 66 389s could not be all "that: heavy. When I was a teenager my dad rebuilt the 66 389 in our 66 Catalina.
I watched him grab the block by the main caps off the garage floor and pick it up and put in on a temporary bench made with saw horses and 2 x 6s.
Had had it bored, I assume .030.
That engine died from a cracked cyl wall 4-5 years later.
It had a good life, took us to Broken Bow OK twice from Cali.

Thanks for replies and good info. I was looking at a motor for sale that was 60 over. Just rebuilt but had issues. Probably sold already, Maybe good that it did.
Thanks again.

I've got 2x '65 389's here that are both 0.060" over. One of them I sonic tested and it would go another 0.020" if I got bored. One is running stock 400 bore Speedpro pistons, the other runs 389 valve relief pistons. No issues with either motor.