High Toned SOB

How much can you go with cast pistons, and what is the biggest killer of them? HP, cylinder pressure, or RPM?
Would like to use forged but not sure if they are necessary for what I am looking for. Single Turbo 350 around 350-400 hp.

thanks

B4Ctom1

the P1sc kit that people put on thier 3rd gens makes around 9 psi and peaks to 11-12. that is stock cast pistons setups. it is intercooled. the head gasket is usually the first to go too.

what kind of compressionare we talking about here?

I have seen some 142 blowers on GM replacement motors too.

89JYturbo

Detonation kills the pistons, not the boost!

Also, if the rings butt ends, that can pull the top of the piston off (so I've heard).

High Toned SOB

Hey guys,
It is a 1990 non roller 350 truck motor. Originally TBI, but now I am still up in the air with the fueling part. I would like to try injection, and as a matter of fact I have a slew of PCM's I went to the junkyard and got, but I don't have the tools to program or burn. My other option is the Megasquirt.
Anyways, the engine is the 90 TBI truck engine. I have it all apart right now, the stock compression ratio is 8.2:1 so the compression is right. I have a older set of 2.02/1.64 mildy ported heads at 72cc, the factory cam is tiny at around .380" lift. I think I will change the cam, not sure yet. If I put a set of 1.6 rockers on it, it puts the lift up around .420", but still not sure if that's gonna be enough.
I was wanting to run a non roller solid cam around .500" lift, cut on 112 or 114 LC, but still unsure about a good one to top off the combo.
Anyways, I am looking for a street friendly 400hp/400tq turbo engine that is "FUN" to drive. Getting tired of trying to drive 12:1 engines around alot.
Thanks for any info and advice.
Mike

B4Ctom1

sure

but I think a 10 pound piston is much too heavy for such a small engine. Heck you will have 80 lbs of piston by the time you are done

High Toned SOB

That's OK, I can mill about 9 1/2 lbs of carbon off. Boy, if you think about how fast a piston travels, and the fact that it has to come to a stop and reverse direction, it's amazing they stay togather. The ideal engine is rotary.

So the general consensus is cast pistons can handle 10lbs, and up to 13, given the timing and fueling is correct?

One more ?

Has anyone PERSONALLY ran a cast pistoned 350" SBC around 400 hp, (naturally aspirated or forced induction) in a street machine for 30K+ miles?
Looking for some personal experience on longevity and issues.
Thanks again guys,
Mike

B4Ctom1

I can tell you that if you replace that 8.2:1 compressiont TBI 350's 64cc heads with some 72cc units you won't have 8.2:1 anymore.

POS350Z

Mike I have an L98 with around 400hp...my car has about 65K on it and runs fine....I'm running 58cc AFR heads (10.1 comp???)...my car has no power adders...and the factory cast pistons....I've been told if your gonna get blown get the right engine pieces first....... BTW your pretty close to where I'm from!

350Z

High Toned SOB

Ok, I bought some 2256 F .040" over's. Thanks for the info guys, any advice on a good cam?

POS350Z, where are you at?

83 Crossfire TA

iTrader: (2)

The 1500 TBI engines were 9.1-9.3:1 and the HD (2500 and 3500) trucks got 8.9:1

B4Ctom1

based on that information, it would give him a ratio range of 8.43-8.59 for the 1500 TBI and the HD (2500 and 3500) engine would be around 8.21-8.26 theoretically by switching the 64cc to 72 cc heads.

anesthes

iTrader: (12)

I used to run 2256s. They held up to 8psi for a while, but 12 killed 'em. Ran 72cc heads too, which came out to around 8.96:1 compression.

My new setup uses a inverted dome piston, and a 64cc head. 9.3ish:1 compression.

-- Joe

B4Ctom1

if your TRW's died at 12 psi I would look elsewhere for a failing.

timing, a/f ratio, or not destroying quench with big chamber heads to reduce compression, or maybe some ring issues.

those piston's reputation speaks for itself in applications nastier than that which 12 psi boost can deliver.

anesthes

iTrader: (12)

I think the problem lies in "intended application".. The pistons were designed for 11:1 tops compression ratio. Not 14:1 under boost.

"Blower pistons" have inverted domes to match the chamber, the ring sits lower away from the fire, and they're usually lighter.

The good thing about a 2256, which is why I always used them, was they are one of the cheaper forgings available, and the weight is similar to a stock cast piston, so you can get away with not balancing the engine.

-- Joe

B4Ctom1

it wasn't an attack, just seeing them in nasty applications with heavier boost or nitrous without failures is what I mean.

Then again it could have been a forging failure.

I have heard about some wierd things going on since federal mogul did their big change over.

Nothing I can substantiate, just heresay at this point. If this is the case then I suppose then there could be cig problems with running this piston with heavy boost.

when you say 12 psi, were you talking nominal or peak?

Beast5spdGTA

I have ~8-10K miles and a little over a year of everyday driving at 10+ psi, but lately been max ~7 psi (due to belt slip) on a stock rebuilt LO5? (swirlport heads and roller cam) 350. That should be 9.3:1 comp with iron heads and cast pistons.

The car ran 14.1 @98 mph at 3600+lb race weight before the boost, so it's probably near the 400 hp mark now.

BOTLFED

Like everyone is saying, detonation is what kills them.. Before getting my tune "right", I broke some ring lands and rings..

So far, my cast pistons have held up to tons of 10psi blasts and a few 16psi blasts..

Stock short block with cast flat tops and 74cc heads..

Cheers,