Thread: Need Help Finding Forged Pistons

Okay, Stop right there. If you read the title and immediately though Diamond Forged, then please dont post. I am aware of the Diamond Forged pistons and am not crazy about forking out the money for them particularly when I can search and find other forged pistons that are considerably cheaper that are extremely close to what I need.

What I need right now is two things. First, complete specifications. I'll list what I already know below. Second, if you know of a forged piston that is a direct replacement for ours and is not a Diamond Forged piston, post that up.

Sock Piston, Connecting Rod and Engine info:

Compression Height: 1.205" (What happens when this number goes up or down?)
Wrist Pin Diameter: 0.905"
Ring Widths: 1.5mm, 1.5mm, 3.0mm
Bore Size: 3.800" or 96.5mm
Stroke: 3.400" or 86.5mm
Connecting Rod Length: ?, L32 Rods in particular
Block Height: ?
Deck Clearance: ?
Stock Head Gasket Thickness: ?

Im having a hard time coming to terms that a Diamond Forged piston is the only option out there for us. The 3800 has been around too long for that to be the case. And even if I have to customize a set I think I would still come out cheaper.

At any rate, I just wanted to see what options there were out there that maybe someone knew about and to get some of the information that I am missing.

I have found a couple pistons that match up nearly identically except the Wrist Pin Diameters. I dont think that would be a good place to use bushings so Id like to see if I can find the correct size.

Thanks in advance for your help.

Have you heard of Diamond pistons?









j/k just had to on that one.

But seriously, there are other forged pistons out there other have used. They don't make them for our cars, but given the specks, they can custom make them for you, and it doesn't really cost all that much, since they make them any size all the time for most every engine out there that uses a piston.

I know I have seen others builds on "the other forum" but cannot remember what company they were going through. But the bad thing is...there is no real R&D on them once they are made, so your the tester, and hope they know the expansion rate of the aluminum they are using and can figure that into the bore size for a cold motor as well as a hot motor. Thats why I went with Diamond...a good known direct replacement upgrade over stock.

~F~

What are your plans? Car's pushing 600+hp are able to run stock pistons.




















Did someone say diamond pistons?

Thanks Farns. I REALLY REALLY would like to use Diamond pistons but after you figure the cost of the pistons, L32 rods, then Ive got a handfull of money into it. And I dont mind that, but I had budget goals for the whole project I had hoped to stay within.

Im hold out hope that someone here has some additional information and short of that I guess I'll save for a set of Diamond pistons. Its overkill for what I really have planned for the car, but I like that safety margin.

After the research I have done so far, I have come to the conclusion that it will probably be a set of customized pistons, but to do that I also need more information about everything so that they get the dimensions right.

Oh, dont get me wrong, I know stock pistons are holding a lot, but they dont like knock very much. Which Im sure all pistons are like that but I want a bit more thermal stability and more resistance to shatter from knock. Obviously I plan to tune and eliminate knock, but I need to plan for something going astray.

And all of this really started from my pursuit of fuel economy and wanting to cryo treat the block, crank and so forth. And if Im going to open up the block, then I might as well take advantage of the opportunity and upgrade things.

However, as I think about it, cryo treating relieves stress in metal, so having a new set of stock pistons treated may also give me what I need. These are things I have to weigh and consider.

yah, sorry I have plenty of time to help look for other similar projects but work just blocked the clubgp message forum, my best bet.

I'll probably get on there later on and see what I can find.

Ross racing has the specs for our pistons, bored .30 over.

Might want to talk to them. I have 13 forged Ross Racing pistons here I'll PM you some pics and specs if I can find the damn extra piston ...

PS. The rings SUCKED ! One of the motors drank oil, and dropped a vavle (crappy Comp cams spring) and the other spun a bearing and popped a ring AND bent a vavle.... The pistons themselves are very strong, the one that had a vavle dropped on it survived and shot the vavle through the TOG's .... The motor was actually still running okay with the dimpled piston ....

oh well, that's what you get for 6,700 shifts and a 7,000 redline .....

I wasnt exactly excited about boring 30 over, but if that gets me what I want, then I suppose thats what I'll need to do.

Man, this little ant hill project with not a lot of cost is turning into Mt. Everest, LOL.

Others have also used JE Pistons and Wiseco Pistons but like Farns said, they are custom made pistons and no R&D so you may be buying paper weights for $500+! I wasnt really crazy about Diamond pistons for a long time either but learned a lot of thigns about them since. I wouldnt buy them coated as Diamond isnt who is putting the coatings on them and I feel that because of this clearances arent properly set and the side skirts wear excessively. Every set of used Diamond pistons I have seen have worn side skirts and all of the ones I saw WERE the coated pistons, while lots of guys have thousands and thousands of miles on uncoated parts. I also feel that people / machine shops arent properly checking or finish honing the cylinders for the right clearances and this is a larger contributor to the problem. Those pistons will take a lot of beating for sure and I cant say I have seen one with a chipped ring land. Scotty I am in the same boat as you are but decided to face reality.... I dont care if there are cars out there making 600+ HP, HOW LONG do they last in real world conditions with thousands of miles of daily driving? Big deal if a car runs 10s or 9s, thats a weekend pass but means nothing to me as that says nothing about longevity under those conditions. Anything at all could go wrong with the fuel system and stock pistons dont like lean at all or they chip. Diamond pistons uncoated from Intense are $699 and include Total Seal rings. My local machine shop deals direct with Diamond and they can be bought a little cheaper but there isnt much markup on them. You can also get near whatever bore you want whether it be stock, .010, or .020 which is really all you need.

Thanks for that info Trannyman, very much appreciated. I wasnt real crazy about getting coated pistons as it was because I plan to have them cryoed and that would serve the same purpose of having them coatd (abrasion resistance) and Im not totally sure how the coating would hold up under the treatment to begin with.

My main goal is fuel economy and durability with occasional track outings. The focus obviously going more to the daily driver aspects. If that means I got beefier parts in there than it really needs then that is fine. But I feel pretty convinced at this point that forged pistons are a necessity as an extra guard against lean conditions.

I havent decided yet on overboring. Im into areas I have not traveled before so research is needed, questions asked and so on. I plan on taking my time doing everything possible I can find out or know of to do things as perfectly as possible cause I dont want to have to yank out either tranny or engine for an extremely long long time.

Since I have the L36, something will probably happen to my bottom end one day if I push her too hard. So, with that in mind, a backup fund is being setup to purchase a L32 bottom end and swap my top end onto it. Seems much simpler and reliable than rebuilding the bottom end or having it built.

That would be an option except I want to open up the block and have it all treated in hopes of reducing friction and installing forged pistons. Im playing in territory I have not ventured in before and so I have an emphasis on making sure my info is spot on and possibly documenting things enough to do a few write ups.

Originally Posted by SyntheticShield

That would be an option except I want to open up the block and have it all treated in hopes of reducing friction and installing forged pistons. Im playing in territory I have not ventured in before and so I have an emphasis on making sure my info is spot on and possibly documenting things enough to do a few write ups.

I'm still learning too, and that's why I will just leave it at "You have larger cajones than I".

Nah, I just care less, LOL. Im not afraid of failure. I dont like it, but Im not afraid of it and when I come out on the other side and everything works but I dont get the results I hoped, then it will be all good. If it fails, I'll try and determine why and correct the issue and try again until I either determine its not going to happen or it cant be done or something along those lines.

But Im never going to learn anything by pondering on paper and theorizing as to possible outcomes. You can speak of many fabulous things, believe in great possibilities or theorize to awesome outcomes but it means squat unless you willing to get your hands dirty, put your money where your mouth is and put it all into practice.

I would try Keith Black I used their Hyper pistons on my last build and ran No2 no problems,I know they make Forged pistons at reasonable prices so try contacting them.

Thank you chico, that name has come up a couple times now, so I'll probably give them a call and see what they have.

I went with a standard bore because the block was in dang near perfect shape, and the cost of running over sized pistons, and paying the machine shop to bore each cylinder did not offset how much more horse power I would make. For somebody right off the bat trying to get every little bit of power out of their engine, and has endless funds to do so, ya, that might work for them, but I could not justify the extra funds for THAT.

When I built my engine, the machine shop measured each piston and machined each cylinder to specks of that piston. Each piston was numbered for that cylinder.

The main caps were installed, with the ARP studs, and then the block was line honed.

The crank was polished.

The L32 rods had the stock bolts and "sleeves" removed and ARP bolts installed, and then the rods were line honed as well.

The balance shaft was removed and they drilled and tapped the rear oil feed hole for me for free, simple task takes 5 minutes.


Machine shop cost for me was $200.00

The shop that did all the balancing of the rotating assembly was local as well. Everything was balanced 50% and I had very little material that was removed from the crank weights compared to others who's ended up looking like swiss cheese. I believe this cost me $100.00 or maybe $200.00 I cant remember. But worth it.

For diamond pistons, like trannyman said the side skirts will be worn regardless after use. This can either come from poor machining and the bores being too big, or just the side effect of running them. Meaning, the Diamond pistons are designed to swell as they warm up. They are cold, and under sized, and as soon as you start your car, sometimes they will knock, and slap the side skirts against the cylinder walls only at the base of the bore when the direction is changed. As they warm up, they will swell, and increase in size, and the piston acts as normal.

Total seal rings, I used the ones that came with the pistons that were already cut to fit a 3.8 motor standard bore. The second time around they were file to fit, so I had to set the gap in them which required me to buy a ring grinder. No big deal it was easy to do after the first couple rings. Just takes a while to install measure, remove, cut some more, install check, remove some more, install measure etc. 24 rings total.

If you go with custom pistons, you also must make sure they, who ever makes them, are aware that these pistons are offset, and are directional. Trust me, it makes a difference.

~F~