[cperform]

I've owned a couple zillion Pontiacs over the last 35 years and a pretty good percentage of 'em have suffered from some degree of blow-by...some just hazed the valve covers every few hundred miles...and some were so bad you could smell it in the car. In the old days, 455s were plentiful and you just swapped one in for a tired 389 or 400.

I've decided to finally freshen up the original 400 in my 69 GTO. It suffered from moderate blow-by...[ and a skip at idle..thinking a bad exhaust valve there]

So I'm going to whip the heads off before I ship it out to the engine shop. I really don't want to spend $3000 or a rebuild...

What are the odds I won't have to bore it? How much of a step on the top of the bore can I live with? Am I going to find broken pistons? Any advice is appreciated.

[74Grandville]

I'd say pretty slim

How many miles on the engine?

Only real way to tell is to measure it with a bore gauge.

[cperform]

I've owned the car probably 10-12 years now...yanked the mill 5-6 years a got and put a 496 chebbie in it. When I bought the car guy told me it had 35,000 miles on it with a big back story...yeah yeah yeah...figured it was 135000 more likely though nothing on the car LOOKED over 100..

Pulled the heads off...no ring ridge at all..zip, zero. [And motor was super clean inside.]

Sooooooooo I guess the 35K is real. I'll leave pulling the pistons to the engine guy but I'm guessing it must have some broken ring lands.