NotDads442

Going to pull my 67 400 in the next few weeks. After reading a tech article from Ray Bohacz in Hemmings Muscle Machines, he seems to believe all vehicles of this vintage should be punched over during the overhaul process. The local machine shop owner said he wouldn't be surprised if my 400 doesn't need it. What is the consensus on these engines with this kind of mileage?

android 211

It's a If the bore has less than a set amount of wear its OK to just hone and re ring it.

Fun71

Since cutlassefi is bringing a good set of light weight forged pistons with a modern ring pack to the market, I see no downside from boring the engine and using these superior pistons and rings over the factory stuff. Your engine should be good for another 100,000+ miles after the rebuild.

https://classicoldsmobile.com/forums...5-pistons.html

joe_padavano

The only smart thing to do is to disassemble the motor, mike the parts, and THEN decide if you need to bore it or not. Speculating is worthless and potentially a good way to spend unnecessary money.

NotDads442

Is there anything I should do to my stock C heads while they're off?
Seems a lot of guys lower the compression on purpose. Is it really that difficult to run the stock 10.5 to 1 on today's high octane fuel? Particularly when you run a high performance cam that bleeds off static compression

Please advise

android 211

The consensus on most boards is 10:1 is about as high as you can go with iron heads and even that is pushing it. Some people get away with it. You'll need to do several things to make it work. Tight 'quench': a piston to cylinder head clearance of as close to .030" as you can get. Running temps of around 180 degrees. a wide LSA cam; 114 and ICL of 110 with 230/240 timing, on the rich side not the lean side in the jetting. Conservative spark advance. Cold plugs. Blocked exhaust crossover.

Sugar Bear

Is the engine presenting problems/issues or do you just want to do a rebuild?
Many times motors are rebuilt just because the owner wishes to; but, if that is the case taking it apart may create problems. Consider doing a leakdown test before pulling it apart and you may find that the rings/pistons are fine and you could do a freshen up on the heads, timing chain etc.

About boring due to the vintage, I don't get it. It measures out ok or it doesn't and that cannot be known until it is apart. As Joe P said speculating may be a good way to spend unnecessary money, if you pull it apart measure it and see what is needed.

Boring obviously removes metal and reduces the number of times an engine can be rebuilt and it can lead to overheating.

Good luck!!!