[chunky`]

2618 expands more, which generally allows them to take more of a beating, so you have to adjust your clearances accordingly. 4032 has more silicone content which allows you to run tighter clearances since the material expands less than 2618, however, at the expense of being more brittle. I've seen a 4032 piston shatter in a high hp turbo car before. Generally I'd say that 4032 is more suited for all motor applications...2618 is more suited for the abuses of a turbo car. I wonder if anybody runs a 4032 piston for methanol FI setups.

On 94 octane, you could easily run 12.5:1 reliably...just make sure your tuner knows and understands what they're doing.

As for coatings, moly skirts are nice...theoretically...wiseco shelf pistons come with these already. If you're going to coat the piston top, you should coat the chambers as well. Heat will be absorbed through the path of least resistance. Keep it off the piston tops and the head get's to absorb more. Personally, i've never seen any measurable differences. I can see how it could be beneficial, but chances are, if you're at the point where you're counting on coatings to make a difference in the overall picture, you wouldn't be asking.

You can safely go to 88mm on stock sleeves...maybe more...

I agree with that. 4032 is great for street motors and just about any all motor build. The tighter clearances should pay off with better longevity of the piston itself and the rings (they're less exposed). The Mahle pistons are 4032, have coated skirts, and generally one of the best off the shelf 4032 piston makers out there. That's what I would use if I was going to start a new build today.

2618 can take more abuse b/c it has a higher tensile strength. That means when high HP starts pounding the piston, high revs start to stretch the piston, and high heat starts to soften the piston, 2618 has a greater ability to take the load without falling apart in a catastrophic manner. The downside is that the coefficient of thermal expansion is greater meaning you have less consistent skirt profile as temperature varies. This makes it a little bit more tricky to get daily drivable longevity out of a 2618 piston versus a 4032 piston.

 

[chunky`]

You and CChang5 make good points. Since I have no plans of boost I should be fine with the 4032 pistons. Could they hold up to stress of road racing? What about nitrous? I'm not decided yet but I'm not ruling out throwing my Zex wet kit with a 50 shot in the car if I'm gonna drag race. Since "weaker" OEM cast pistons can handle moderate nitrous and aren't a major no-no with racing, I don't see why I would be assembling a "ticking time bomb".

I was looking at the Mahle pistons but they only seem to make RSX 86mm pistons. They MAY make 87mm piston, but I can't find them on the internet. Maybe I'll get in touch with their customer service.

Anyone have any experience with the Supertech pistons? They make the 4032 pistons with a 87mm bore and a 12.5:1 c/r. Thay also come with a "'phosphate dry lubricant’ coating to protect the rings against ‘micro-welding’ and enhance lubrication on the skirt/cylinder area."

You could definitely do nitrous on a 4032 piston. I wouldn't do a large shot, but 50 shot should be fine.

Mahle does make an 87mm piston. Check their website for a part #, I looked it up not too long ago.

I'm about to give the supertech pistons a whirl. I'll let you know how they run in a few months once i get some miles on the motor. The main caution with them is that the spec sheet has a clearance recommendation that is way too loose IMO. I have a lot of discussion on that in my latest engine rebuild thread, search for it.

 

[chunky`]

I looked it up and they do have one 87mm piston meant for the RSX. Its a 12.7:1 c/r with RSX so that like 13.2:1 with K24 block and K20A2 head? Too high for 94 octane?

I'm really interested to see how the supertechs work out for you. I haven't seen anyone running them. You running the 12.5:1? If you remember, let me know. I'll check out your thread for sure!

The compression ratio will be higher, but you can always remove some material on the piston or use a thicker head gasket.

Yes, I'm running the 87mm 12.5:1 supertech pistons.