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I am looking for a rebuild kit for a 425 ci motor.
I want to do it from the ground up, (if it needs bored out, piston, rods, you name it)
any suggestions?
Last edited by Dave Wilcoxon; Dec 30, 2024 at 05:58 PM.
Parts aren't that hard to find. The only real 425 specific parts are the crank, rods and pistons. (and possibly the block/cam) The rest is standard big block Olds - 455.
You need to figure out which 425 block you have. Is it a 39 or 45 degree lifter bank angle? Is it a .842 or .921 diameter lifter bore? If the block is 45 degrees then your looking at a non-standard cam grind. If the lifters are 0.921" then you'll have a harder time finding a quality lifter in either hydraulic or hydraulic roller.
For the 425 I found that good piston selection is limited to .030 over. (Mahle Pistons 197816355) You can go .060 but hard to find a real nice piston unless it's custom.
There are some places that will sell you a rebuild kit, but the reality is your better off sourcing your parts individually from places like Summit, Jegs and specific quality Oldsmobile vendors.
I built one with Mark's help sourcing some of the parts. Mahle pistons, Rocket Racing rods, internally balanced, Edelbrock heads, roller cam, Performer intake, Sniper EFI...
Its what I wanted at the time, and don't get me wrong, its a good engine for what it is. But if I had to do it over again, I wouldn't. Its a hell of a lot of money and it doesn't make the power a more common 455 would, much less a stroker kit in a 455. Unless you're really looking to keep the car original, I'd go for a bigger big block. It'll cost the same and make more power everywhere. Even if you don't want more power, it'll have better street manners for the same cam. There's nothing a 425 can do that a 455 (or bigger) won't do better.
Last edited by Bubba68CS; Dec 30, 2024 at 06:13 PM.
What is the reason for the rebuild/what are your goals? Is it a high compression motor?
Selecting individual components suggested by our CO member engine builders will result in a more powerful and drivable engine vs. a kit.
I'm doing a complete rebuild on the 442, I bought a Roadster Shop frame and suspension, I really like the 425, my wife and I are going to drive the car across country as a road trip car.
I bought the car in 1979,the gentleman pulled the 455 and put the 425 in it to drag race. I did a partial rebuild in 1985, then put it in storage for the last 20 years.
I wanted to restore it before I got too old.
I'm doing a complete rebuild on the 442, I bought a Roadster Shop frame and suspension, I really like the 425, my wife and I are going to drive the car across country as a road trip car.
That's a hell of a lot of money to invest in mediocre performance. Your car though. Talk to Mark (cutlassefi). He can set you up with rods, pistons, cam...hell he can build the engine for you if you're close or willing to ship to him.
You have been around this site for a while so what I can offer you probably have already seen but here goes! If truly a 1967 motor, it will have the more common 39 degree lifter bank angle. If it is a Toronado engine block, it will have the 0.921" diameter lifters versus the more common 0.842" diameter lifter. These are/were great motors and you have the option of keeping the 425 crankshaft and/or since you will be changing pistons and rods you could put a 455 crankshaft, pistons, and rods in it; maybe even a stroker kit. As mentioned in previous posts, contact Mark, cutlassefi on this site, or one of the other Olds gurus such as BTR or Rocket Racing for your build. Good luck and keep us posted!
I will keep you all informed as I buy parts and get the motor done,
I fell in love with this car the first time I saw it. Hence the reason I still own it after 45 years.
(the color on the car is Bamboo Cream)
