Oversize pistons?

[TAK65]

Hi all,

had the engine lifted out yesterday (1963 slant 225). There is a ridge in upper cylinder walls, the guy who will do the rebuild said it will probably need to be bored .030 over (is now std), the machine shop will tell later if this is right.
I just would like to know beforehand, which sizes are easily available? And what would be the wisest choice for a dependable stock(ish) engine?

Thanks,
Tina

 

[xLURKxDOGx]

Usually it depends on the manufacturer but most common ones are .20-.30-.40.-.60

Jake

 

[65 Dartman]

I bought 30 over Sealed Power pistons and rings through Amazon

 

[BillGrissom]

30 mil over is pretty standard, since I see pistons for that regularly. The risk is going so far that the cylinder walls get too thin, which requires ultrasound testing to determine, but not usually an issue for a slant as I understand. We assume the guy determined the ridge was actually metal and not just carbon. You can tell when you use a "ridge reamer" to remove it so you can slide the pistons out. Besides the ridge, they must overbore to make the cylinders round and so the centerline is in the correct place.

 

[Charrlie_S]

I would recommend either .030 or .060 over size. The rings are easier to get. Personally I would go .060 if the cost of the machine work is close to the same. That way you don't have to worry that .030 would leave a small area, that didn't clean up properly. Slants can go more that .060 safely. Many have been bored to more then .100 over.

 

[KosmicKuda]

My 97,000 mile 225 is .040 over. Why? Because when I used a brand new ridge reamer I rented for free from Autozone, it damaged that area too much to clean up at .030. My machinist said I should have just pounded the pistons out from the bottom since the pistons were getting replaced anyway.

Pistons are Silv-o-lite, rings are Hastings, and bearings are King. All were in the all in one rebuild kit. My excellent machinist who was doing this since 1962 said those were all good parts and I trusted him explicitly. One problem with going directly to .060 over is that it leaves little metal for the next rebuild. The added displacement between 40 and 60 is negligible.

Hey, we're not building a class racer here, just a car to drive on sunny afternoons.