Just confirming: I'm running .030 pistons on my rebuild: bores check out at 3.43 . I'm thinking minimum ring end gap for the top ring should be approximately .013, with the lowers at .017.

What would be a comfortable range for both compression and oil rings? Just to be content that I'm not butting ends and yanking this thing apart again, I'd prefer to run with a slight extra gap to be sure.

What do people recommend?

I wouldn't go under .015 on the top ring personally. Or a little more. Too much gap is much better than too little. On the second you might shoot for closer to .020. With the 100mm bore turbo motors I'm used to building (non slant) I use .020+ on the top ring.

As an FYI...
Ring gap applies to the top & second rings only. (compression rings)
Oil ring (sets) are set by tension ratings.
The standard tension should be fine for your application.
DD

Got it. Thanks robertob. And Doc for the FYI: needed to think about that and I was forging ahead without thinking.

So the FSM states compression rings should be anywhere from .010-.020. I assume this spec relates to stock 3.40 pistons, not oversize.

I guess being in the .015 range on the top and .020 range on the bottom would set me up ok. Any scenario where I might need a little more than that on top and bottom?

http://www.enginebuildermag.com/Article ... _gaps.aspx

these guys reckon .0035" gap per inch of bore diameter minimum.

Brendan.

_________________
1963 AP5 Valiant 225 PB 904 Stock except extractors & 2 1/4 inch exhaust.


1962 S series valiant 225 PB auto. factory every thing. Full restoration job.
Currently on hold till AP5 is on the road.

You will be fine at .015/.020.