When I bought my last 94Z28 the guy told me it had a complete forged bottom end. To make a long story short I was running 8lbs of aftercooled boost for about 25,000 miles. After the car was totaled I pulled the motor apart and found that the rods were stock and twisting and tearing up the bearings. The crank was stock and cracked. The pistons were TRW forged flat tops at 10.25 CR and were fine. I had about 500 rwhp with good tuning and if the car wasn't totaled the engine would have blown shortly. Bottom line is I wouldn't go with stock rods and crank with more than 400 rwhp for reliability. You may get lucky but why take the chance.

 

100% positive that they are not forged At high horsepower/boost levels, I was more afraid of the block coming apart than the pistons....

 

These motors just do not like boost. If you drop the Cr, it might be safer, but most people pop stock motors with 8-10 psi of boost after some time. I would save up some rebuild money just in case, if you run over 8 psi, even if you drop the Cr.

I see some people trying to compare Buick pistons to LT1 pistons.. I would have to say don't bother. Totally different engines. Lt1 pistons have proved themselves weak, and detonation is not necessary to wipe out the ring lands. Most people do have detonation when blowing these pistons out, but I have seen one car in particular with a real conservative tune crack 4 pistons with absolute no detonation at all. It was on a dyno and the snapshot info showed no detonation when it popped.

Some people do get "lucky" and run 10 PSI on these cars stock for thousands of miles.. The question you want to ask yourself, is .."Do you feel lucky or not"

 

If you need to save money for a rebuild then the only way to really enjoy the blower is to put it on your desk and polish it once in a while.

Hypereutectic pistons are strong, but also very hard and brittle. Boost + perfect tuning and you won’t hurt them. The first time your tuning gets messed up, you get a load of bad gas… and that LT1 will be doing a choo choo train imitation if you’re lucky (If you don’t know what I’m talking about the next time someone hurts a piston/ring land pull the oil fill cap while it’s running an watch, it looks like an old steam locomotive).

At that point (if you were lucky) you’ll probably just need a bit more machining then normal to rebuild it. If you were unlucky you’ll probably need a new block if the bore where the ring lands fell apart can’t be cleaned up. If you’re really unlucky, the piston will come apart, jambing things up, sending parts through the side of the block… and you’ll likely need a block, crank and quite likely work to or replace the heads.

 

9-PSI on a "perfect" tune with no detonation and pistons went bye bye

Sometimes pressure alone will destroy these pistons from what I have seen.

 

Yes, but what compression ratio? If that was on stock 10.4:1 pistons, 9 psi is surely too much. This thread began asking if the stock bottom end at 9:1 compression could take 8 psi with hypereutectic pistons. The answer is a resounding "possibly". Other factors could be if it is intercooled or not, and also, how much it is abused. And, a 'perfect' tune might not be the easiest one on the engine. I ran mine with a little richer than perfect tune for safety's sake.

 

Well...it may have been the stock 10.5 to 1 ...but no matter what....our pistons still blow donkey *****. You can't argue with that.

Joe

 

Joe,

Yes, you can argue that. I made over 500rwhp, as have plenty of other people, with the stock bottom end, AND put tons of reliable miles on it. That's 600 crank hp - for factory pieces, that's not all bad. Sure, you are asking for trouble running 10.5:1 CR and boost with the stock pistons, but I'd be reluctant to run that high of a compression w/ boost on any pistons.

 

Okay....similar comparison. When the Hollywood people were on tv talking smack about bush and the war....did you think that was the opinion of the majority?...hell no. Same thing with pistons....I seriously doubt that the number of people with no problems (500rwhp) is very high....that's plain crazy. Just using common sense here by the way. Hell....I know plenty of people doing crazy crap with no problems so far.....there is a thing called luck.....and all of it can be argued. Thank god everything here...even my opinions of course....is an opinion and not fact.

Joe

 

I know at least 2 local guys (who's cars I worked on so I know that they're not just talking smack) who are in the 10's with stock pistons..., one has been running on the same short block for over 4 years now. How much HP does it take to run 10's in an f-body?

 

It takes more with a blower than N/A or nitrous that's for sure. The power comes in alot higher rpm than with nitrous.

Joe

 

A poor analogy, at best... regardless of whether you realize it or not, the people that have the 500 hp setups on the stock bottom end generally know more than the poor saps that blow up their 350 - 400 rwhp blower setup and then cry foul. This isn't always going to be the case, and there is always going to be some degree of 'luck' to it, but I don't think luck isn't as big of a factor as you're making it out to be.

Anyway, I stand by what I said- if properly setup (low compression), the stock pistons will work fine with the amount of boost the orginal poster wants to run.

 

My whole thought behind this was the life of stock pistons on lower compresion.

Many people bolt up superchargers to totally stock motors and they have 1-5 years life with them. So i though, 8# or less with stock pistons on lower compression has to be better then the people running totally stock motors and superchargers.

 

you are probably right.............BUT, there is no guarantee.

have money saved for a rebuild, cause it might last 2 years, or it might blow up in 2 weeks.

 

That's the point we've been trying to make, but some people won't listen. They keep saying our pistons are weak "just because (so-and-so) blew thier stock engine with boost in X,XXX miles." Then they turn around and say they were on stock compression. But practically NO ONE has dropped the CR before on our stock bottom ends and run boost. Dropping the CR by 1.5 points takes A LOT of stress off the pistons. Why do you think the Top Fuel guys run 6.0:1 compression? That's right, so they can run massive amounts of boost (over 50#s) using nitromethane without blowing the engine into a million pieces.

I think it takes about 500-550rwhp to get your average full-weight f-body into the tens. 125 traps maybe? I know a local guy that runs 10.90s at 125mph, but he has yet to dyno the car.