View Full Version : Lowering Comp on a Nail Head

11-01-2001, 06:37 AM
Hello all. New to the Buick forum. I have quite a few questions, but I'll start with one. Are there any off the shelf pistons for the 425 available that can get me in the 9.0 to 9.5 area?

I have a chance to obtain a running 425 and would like to use it in a future project (undecided as of yet). And would like to know if there are any road blocks with building the 425. I've never run a Buick mill before, so any info would be of great help to me. I'm not looking to make a screamer out of it, just a good tractable pump gas motor. And just generally like the style of the Nail Heads. Thanks.....Los

Dr. Frankenbuick
11-01-2001, 04:47 PM
The first road block you will run into is finding pistons. No one is making cast pistons. They are available, but the price for a set of cast pistons is close to $400. Then if you machine off some of the dome to lower the compression, you could almost have a set of forged pistons made. My 425 project is on hold for that very reason. I have everything else, but can't get past the cost of custom forged piston.

Steve B.
GSCA #2173 (1986)
67 GS 525 Stg IV
66 GS Convertible
65 GS HT
63 Riv

11-02-2001, 01:10 PM
Thanks for the reply Dr. Yeah, I was looking into pistons and was of the mind I would have to have a custom set done up for it. Not cheap to say the least, but I think it would be well worth it in the long run. Besides, I've always wanted to do something with a Nail Head. And I'm getting the running 425 for $150.00, so maybe that will make the piston $ easier to swallow.

There's just so much research for me to do as I'm not at all familiar with Buicks. Drove a couple of Nail Heads, but never owned one. I Would like to mate it with a 5 Speed, but I don't know if that's an option yet. If I'm not mistaken, it's a different bellhousing pattern from the more common B-O-P bellhousings. Totally undecided as what it will be installed in. About the only thing I'm sure of right now is I will get the mill. Thanks again.......Los

11-10-2001, 02:24 PM
Hello, the infamous Jim Jacob's '34 Ford 3-window coupe had a nailhead backed up with a muncie 4-speed (built in early 70's), so there are adapters out there, but it may be tough to find one. Some companies still make adapters (Offenhauser for one), so I'd start with them. One idea is to mate up 2 adapters which are still available (nailhead to early Ford, early Ford to Chevy), but haven't seen this done. Keep us posted, I'm tempted to put a manual behind mine as well ! If I find any info I'll be sure to post.