blu00rdstr

What are the best pistons for high boost applications?

I broke uncoated Diamond forged with detonation when I overboosted by 3psi.

I broke Mahle forged pistons before I even got home with 1/2 throttle and less than 10psi due to their design (they have no quench deck).

What's best for high boost street application? I'd like a good piston design for a 6.125" rod with:

• strong ring lands
• not too much flycutting or deep top ring down distance
• good quench deck
• about -9cc or more dish
• top and side coatings
• full floating pin

Anything I'm missing?
Suggestions?

sleepersilverado

iTrader: (1)

Je...

mattr228

iTrader: (10)

Wiseco / JE / Ross ...... personally i would of stayed away from both of those your just listed


make sure your compression height is suitable for your application

blu00rdstr

How do you do that? I had .045" GM MLS gaskets, which is good for pistons with a zero deck height. Rocked and cold, the Mahle pistons have a max of .0237", so half that is .012" deck height(rounding up). That leaves .033" clearance, correct? I've read that .040 is close for steel rods, and .060" is close for aluminum rods.

J&J Speed Shop

iTrader: (8)

I consider Diamond and Mahle both very good pistons use them from time to time at my shop. Both these pistons broke because your tune wasn't on, and you were detonating them. Even a forged piston will break no matter who makes it with continued detonation

Why would you stay away from Diamond and Mahle, FYI I built a 650whp (725-750fwhp) car a couple months ago with Mahle pistons. I know W2W made 1200 hp with these pistons also.

Beast96Z

iTrader: (21)

I would have to point fingers at the tune also. Detonation would have killed any piston if sustained long enough. Best thing to do is, get your new pistons and specify that they are for a blower application. The coatings will help also. FWIW, the GM MLS gaskets are .064, not .045.

blu00rdstr

I think those were the Mahle Turbo pistons, which are different from Mahle forged.

The problem I have with the Mahle pistons, is that I discovered they have no quench deck. Below is a pic of a Mahle Forged -9cc piston which is fully dished, and of LS1 heads. You can see where the quench deck is on the head, but there's nothing matching that on the Mahle design. Here's an article on quench: http://chevyhiperformance.com/techarticles/94138/

blu00rdstr

I measured them at .048" used and uncompressed.

Beast96Z

iTrader: (21)

I'm confused as to what your trying to say. Your pistons are out of the hole, just like all LS-1's. I'm trying to figure out what you mean by quench deck on the heads matching the pistons. That's somewhat confusing.

blu00rdstr

From what I understand, there's supposed to be at least .040" clearance between piston and cylinder head. A .045" gasket and .012" deck height leave .033" clearance, which is too close.Here's a pic of a Diamond dished piston, notice the flat quench deck between the flycut and side of the piston.

mattr228

iTrader: (10)

compression height is from the center of your piston pin to the top of the piston possibly aim around 1.250 for power adder applications

give the guys at J/E a call and see what they ultimately reccomend

blu00rdstr

The Mahle forged 6.125" rod pistons have a 1.314" compression height.

calongo_SS

iTrader: (7)

.033 is a little tight for a street motor, but will work fine. .035 - .04 is what I have heard to be ideal for a street motor.

Solid346

to me , CP pistons are the best. All bennett Racing boost engines are cp pistons included, its little bit pricey but nice pistons

Beast96Z

iTrader: (21)

You can get away with the .033 quench in a mild application. People run LS-1's pretty tight these days. As long as your static compression is ok and the tune is good, you should have been able to go with .033. Personally, I wouldn't run it that tight. I aim for about .040 to be on the safe side. I still don't know what is up with the GM gasket thicknesses. The MLS's are spec'd at .064 from GM, but yours obviouslly measured thinner. On your next round, I reccomend using a Cometic .054". At least you know your problem won't lye in the gasket thickness. Was there something in the head desighn of the Mahle that was diffrent from your Diamonds? I'm still trying to figure how you said there was no quench deck. A pic might help. You should also measure your deck height with a dial indicator on th eblock. Using the math might get you close, but the only true way to know is to measure it in in the block.

blu00rdstr

I did have .057" Cometics, but they blew out so I installed the GM MLS and have had no problems with the GM gaskets.Quench is the flat area of the head matched by a flat area on the piston. There's no flat area on the Mahle pistons, just a 3/16" ridge around the edge of a large shallow bowl. See the pic of the Mahle higher in the thread, I have a straight edge across it and the dish in between. The pic below shows squish on the left created by the flat quench area between piston and head.
I measured the deck height with the tail of my dial caliper, this is the best pic I could get.

blu00rdstr

So the top pistons so far are:

JE
Wiesco
Ross
CP

J&J Speed Shop

iTrader: (8)

There is no problems with the Mahle pistons, cause I just made 650 rwhp with them on the dyno. Quench is very important in an NA engine, less so in a boosted engine.
Having a large quench isn't what killed these pistons, it was your tune or incorrect installation

BTW factory LT1 engines had a hugh quench area, .060"+ and they ran excellent

Phil99vette

iTrader: (11)

Honestly you need to address your fuel system and tune before you start throwing money @ your shortblock. Spend alittle money there and you will be happy in the long run.
Phil

NA$TY-TA

iTrader: (21)

Exactly ...... u even said so yourself.... detination killed your first pistons........ my first thought would of been get rid of the detination... not the pistons........
Sounds to be the tune is way off and its one of the most importnat things.....