Mike
If ya are running a short compression height the ring pack may not have enough room to put the thickness needed to support your rings in the pressure you are giving them.
If ya can't get it solved,call Probe industries and talk to Shaun and see if he can help. He is in charge of the piston making process out there.

 

I would be willing to bet almost anything that your car would be fine with good engine management (FAST/BS3/etc), and good fuel (race fuel).

It's really no suprise to me that you are destroying engines with pump gas/methanol/stock pcm/crane hi-6/superfuelers/impedence converters/etc/etc........

 

Correction: I don't have the Superfueler anymore. Replaced with 84 lb/hr injectors.

Also, I simply refuse to run race fuel in a true street car. There are turbo cars in the mid 8's on pump gas.

 

Ya could put it on fuel until ya got the tune sorted then put it on pump gas. Might save ya some parts.

 

Okay, but from my perspective it doesn't seem to be working out too well for you. (and I know the cost of fuel is high, but probably still cheaper than pistons).

JMHO

 

So how's the BS3 working out anyway?

 

Don't want to hijack this thread, but basically it's working great

Cruise on pump gas, with race gas on demand.

 

Mike being too lazy to search, are you running a 5.7 or 6.0" rod? if its a 5.7" rod, you have some extra meat, but with the 6" rod, you are really fighting space to get some strength between the ring lands, I think if that is the case, maybe you should investigate the shorter throw rod and different piston. otherwise maybe go back to a 355? I know its kind of drastic, but if you are running felpros, you are gonna be able to afford a new rotating assembly just in gasket prices.

Chris

 

I'm running 383/5.7" rods. Next time I pull the motor, I'll probably switch back to a 355 for meat on the pistons. Not to mention, there doesn't seem to be any power advantage to running a 383 with a T-76.

 

Headers seem O.K.... but, my crappy welds will probably not hold up. I do have a couple of leaks around my welds. Never did get it on a dyno and only got it to the track once. Only did 2 runs at 19psi or so and it did a 11.1 @ 133mph in a full weight convertible in August. With the 6 speed it is such a dog off the line and takes a few seconds before the turbo gets spooled up. With an auto and some tuning it would probably be a low 10 sec car I hope.

 

I gotta say that doesn't make sense to me. He knows it wasn't going lean, so what are you getting at?

Have you called SRP and sent them one of the destroyed pistons?

Rich

 

What I'm getting at is exactly what I said. I think the car would be fine with good engine management and fuel.

Methanol injection is crude (and hows distribution through an LT1 intake designed for dry flow?) , so is adjusting timing with a crane hi-6. Air fuel may have shown 11-1 on the wideband, but how much is it skewed by the methanol that likes to run at 5 or 6-1 air/fuel?

 

Abviously you gonna buy new piston. Try JE heavy duty piston. I have run this piston on my 383LT1 with chilled water to air intercooler boost 20psi, no problem.

 

FYI, you should not be breaking pistons due to the 383 piston height, even with the 6" rod setups. Never broke an SRP yet.

How did you document your 11:1 wideband reading? Was this a datalog from the actual pass when the pistons broke?

With a stock computer, a dyno tune means little unless you race under the exact same conditions. The weather drops a few degrees & you pick up boost with no computer compensation. With the MAF maxed, you have no additional correction. This should happen on your motor at 4500rpm or so.

I have gotten to a point that I will not build a serious engine for a forced induction application with the stock computer. 8-9# boost is one thing, but once you start maxing the MAF out, it is a crap shoot after that. I've tuned many stock computers in the past, but I can honestly say, it is not the proper way to do things. I'm sure some here will want to differ on this opinion, but if they haven't already learned the hard way, they eventiually will. Once you buy an impedence converter, tuning software, a wideband & pay for dyno time, you are only a few hundred $$ from a good aftermarket computer. Pistons, head gaskets & the torturous hours of replacing these parts will justify the extra cost.

Trust me, if you are breaking these pistons with under 800hp, something is wrong.

 

It's not skewed at all. A TechEdge wideband reads lambda from the O2 sensor. It then converts it to A/F ratio assuming gasoline. So, a lambda signal of, say, .8 would correlate to an A/F ratio of 11.6 on gasoline. Now, if you were to run straight Methanol tuned properly, the lambda would still be .8, but the reading would still be 11.6 even though the actual A/F ratio is around 6. You see, as long as you tune for lambda, it doesn't matter what fuel you run. You just have to understand that the readout is meant for gasoline.