I know a guy wanting to build a 4.150 or 4.250 stroke 400 block engine. I've looked at Scat and 440 Source stroker kits. I would like smaller (more modern) rings like .043/.043/2mm or 1.2/1.2/2mm. Does anybody make an off-the-shelf piston for these motors like that? I know Diamond will make customs, but $$$. Thanks.

Diamond used to do a one or 2 changes to a shelf stock for a small upcharge, I guess that is not the case anymore ?

I would try RaceTec pistons. They are extremely easy to deal with and have a lot of stuff available that may not be in the online catalog and will make a few minor changes with no or low upcharge.

AG

I'll call and ask

They have two different brands, Auto Tech and Race Tech, I've used both with no issues, so far
The owner was one of the people involved with J.E. pistons originally, he has been around a long time.

Mahle uses a metric ring stack. S/F....Ken M

I've heard of those. They look like the best of off-the-shelf so far.

Might also try JE.
Mahle has a very good rep, last I heard.

In any case, one would think that the narrower rings would almost be default for performance pistons.

Racetec may make the change for free. Post-COVID nothing seems to be free any longer.

Even still, I'd be shocked if anyone would be cheaper.

Mahle makes excellent pistons but they don't have many choices for BB Mopar engines. We push most customers into Mahle pistons if they carry a good one for the customer's application. Mahle has a very big line of Chevy pistons and they even have a lot of great Ford pistons but Mopar just isn't there thing. You can get a good 505 piston from Mahle but compression ratio choices are limited. I'm using Mahle pistons in my the Ford 521 that I'm building. They are great pistons, just don't expect a lot of choices for a Mopar.

They make a 1.12 CH flattop and reverse dome, which stroke are you running 4.15 or 4.25? Either way could work, using a BBC 6.700 rod for the 4.25 stroke and deck the block .040 or so to get the depth in the bore you want. All my 400 blocks have wound up around 9.965 or 9.960 to be square and flat anyways. S/F....Ken M

Have you checked into ring spacers, as used by superstock/stock racers to get around ring rules?

I really liked the -12.5cc dish, 1.32 CH piston that Diamond sells for the 400 with a 4.25" crank. Unfortunately the price has nearly doubled in ten years.

My current go to is Mahle and thankfully the 2023 catalog lists 1.320 CH offerings. The only dish piston I see listed is stock 440 CH.

Also of note is that Mahle makes a gas nitrided steel top ring that is sold only as a top ring package to go with the 2nd/oil ring provided in with the piston kits. This saves $100+ over buying a complete set of hellfire rings.

Here is the 2021 Mahle ( pronounced mah-la) offerings for mopars

In comparison here is the 2023 mopar section. All B and RB pistons are 1.5/1.5/3.0mm

What I don't get with nearly all Mahle pistons is that they yield a way too high compression ratio for pump gas if building a stroker. The only option is to use iron heads with 88+ cc chambers. They completely ignore all engines that use modern aluminum cylinder heads which have combustion chambers between 72 and 84cc.

That 1.320 is a great CH for the low deck ... to me anyway ... you can use it with multiple strokes all the way up to 4.25 with just a rod change. That's a great street piston , would be nice if they made it as a flat top to get a little more squeeze ...

What is too a high compression ratio for you in Europe, I don't really see an issue with 10/11 with a good closed chamber design aluminum head here in the states , I could run something like that all day on 93 ?

Thanks for everyones ideas. The Mahle looks the best off-the-shelf but the ring spacer idea sounds good too. I'll check the Diamond price but I've got a bad feeling about that. I'll look at these ideas. Thanks

Check Mahle!

I'd call Racetec. They'll give you options for minimal cost. Or, just buy the Mahles as they have clear advantages in a shelf piston. I don't think you can go wrong either way. Diamond is going to be quite a bit more expensive.

https://www.lsxceleration.com/search.php?search_query=Mahle+pistons&section=product ofttimes has deals on Mahle pistons for the LS guys(I got a smokin' deal on two sets I bought there) I'd call them with the Mahle part umber and the best price you've found and see if they'll beat it. Great no BS shop.