custom forged pistons

[brian89gp]

I'm looking for suggestions on the design of some forged pistons for a turbo application. The design would be based on the stock cast pistons of course, but what improvements to them?

Only thing I got is a full float larger wrist pin that can take the stock 327 rod without bushing. The top will also be dished slightly to drop the compression, but how far?

[Dave]

do the calculations and set it down for 8.5:1 with valve releifs for those folks who'd like larger cam's with less worry about taggin' the valves upon the timing belt going out, even at HIGH rpm's.

stronger skirts, STRONGER skirts, I don't think I could emphasize this any more.

I've seen people talk about 3 compression rings and then the regular oiling rings, not sure how well this would work, but it may be something to look into...

--Dave

[SappySE107]

I would deal with quench over worrying about compression. I have no idea though what shape or anything, but you would want to take into account rod stretch for whatever RPM you wanna run to. Boost should help buffer the rod though as well with the right overlap.

[Guest]

I would look into a slightly thicker first ring land or the top ring land on the piston.

If you can have that thicker then a stock piston. You want to try and keep that top compression ring farther down to help keep it cooler and it also adds a bit of thickness to the piston.

If you look at a turbo piston compared to a n/a piston the top ring land is thicker on the turbo one.

shaun

[brian89gp]

How much would a custom set of rings cost?

[RacerX11]

I picked up a set of Hastings rings for ~$115. They are from a Holden V6 race application (I think touring cars). They have a 1/16" top and second ring, which is just slightly thicker than the 1.5mm standard 60degV6 rings, and a 3/16" low-tension oil ring. I don't remember the exact specs off the top of my head, but I spent a lot of time on the phone with an engineer from Hastings motorsports department, and these were the rings they reccomended for a FI or nitrous application. They were very helpful with discussing my alternatives. The Hastings part number is 2M4949. I will try to find the other info I have on them.

The 92mm standard bore is 3.622", which is kinda oddball, but if you bore/hone your cylinders out to 3.625", this is very common, and there are quite a few off-the-shelf rings available. When you get the cutom pistons made, they can cut the ring grooves to whatever dimensions you need.

Marty

[34T]

no comments or experience with "gapless" rings here? I was hoping someone would post something on that. It seems to me that they are quite common in a lot of racing applications......? and so they must be able to hand high cylinder pressures etc.
Anyone with any input on this?
I have been thinking of going that route when I build up my spare 3.4 for turbo use.

[SappySE107]

I have them in my 3.1, and the DOHC. I dont really have much input though because its hard to compare them to an identical engine with just that for a difference. They work, thats about all I can say.