I get nervous about recommendations based on someone's idea of what "should" be ok. But I do agree that detonation is a major cause of piston damage in a blower setup. Heat is the other. On that basis, I guess 8psi on a stock bottom end with low compression would be "safer" than 8psi on a motor with higher compression.

But is it "safe" enough for the original poster? Without data to back me up, I would want to be pretty conservative and say "I'm not sure". I know of no one who has tried it. If one were to try it, being sure it was rich (AFR not >12.5:1) and without much timing (maybe 28-30 degrees) would be important safety measures as would using the best gas available. But I wouldn't place any bets on longevity, especially if it were beat on a lot.

Rich Krause

 

My whole idea behind this was to enjoy the blower while i saved money for the rebuild. I just wanted to see if i might get 50,000 miles out of this setup. It is not a daily driver, nor serious drag. Just wanted to spend some money have a seriour car to drive around it and save money for the rebuild.

It was this idea or go straight to rebuild with high compression and nitrous. Boost is much more better to me but don't think i could fund it all in one project and feel it would cost too much to rebuild then later add boost.

 

My results may be atypical, but I had 108,000 miles on my completely stock (except for injectors and MSD BTM) engine, 90,000 of it with a 7 psi ATI procharger with the 2 core intercooler. I'm currently rebuilding it, but only because the crank shout got fubar'd because the center bolt was left out 2 summers ago when the optispark was replaced, and the cast hub worked its way off the end. Even though the crank snout was scored, I didn't have time for a rebuild, and just put a keyed billet hub on there. It held fine for 2 years, but finally mangled the crank keyway, and cracked the billet steel crank hubs. Had that not happened, I bet I could have gotten another 50,000 miles easy. The crosshatching is still visible on the cylinder walls, and the bearings show very slight wear. There are zero signs of detonation on the pistons, just even carbon soot buildup. If you're at 9:1, and don't get greedy and keep the boost below 10 psi, you should be fine. Go above that though, and if the pistons don't break, it may be the rods. Keeping the RPM reasonable helps a lot, too. I never went much over 5500 rpm. And I have to give credit to Mobil 1.

 

I respectfully disagree. ALL turbo buicks come with hyper pistons with 8.5:1 CR. I regularly turned 25psi on a near 100K mi engine before my trans blew. And I know of a few approaching 200K mi on the stock shortblock and turning deep in the 11s and upwards of 30psi with not problems. Hypers are not as good as forged obviously, but they're certainly stronger than cast pistons. Just stay away from detonation.

And from looking at the two, the LT1's pistons seem to be a much tougher design than the buick's.

Get that CR down and I believe it will last for a long time, pending on how your mains hold up to the added pressure.

 

Not sure why turbo buicks are so tuff, but in 90 percent of the boosted V-8 cars i see run forged pistons for a reason. Hyper pistons are suppose to have a longer life, but you see them blown up all the time. Not to many blown forged on 9lbs. So i would do it right and spend the money to not worry.

 

Hey, that reminds me - I had almost 140k miles on my T-types completely stock long block, and there was rarely a day that went by without 18+ psi of boost going through it. C-16 in the tank? 26-28 psi. I've talked to Jack Cotton (big turbo buick tuner) a few years back, and he insists that forged pistons aren't needed in the turbo regals unless they are into the 9's

The hypers blow up because people detonate them, or the gap closes/butts... there is no magical relationship between hypers and boost that will make them break no matter what the conditions. You see a lot of people running forged, because they probably blew their hypers up because of too much compression, and blame it on the pistons. Guess what, it's not the piston's fault! You're asking for trouble with 10.5 to 1 and boost, forged or hyper...

 

He said he doesn't want to tear the shortblock down right now, and lowering the compression should let him run boost without it blowing up anytime soon. It seems that when the LT1 hypers let go, 90% of the time it is the ringlands and not the face, skirt, or pin supports. Maybe the buick ringlands are better, I don't know.

Hypers are light and make good blower pistons in a street car, as long as you take care of them (low CR, no detonation). But when it comes to serious racing or extreme boost, I agree with you 100% about going forged. You can't beat it.

 

I wonder if perhaps since the Buick hypereutectics are specified for a factory boosted engine, that the rings are further down the piston, so they have thicker top ring lands. IOW - hypereutectics are ok, as long as they are designed for the intended application. What about all the other factory supercharged cars? Surely they don't ALL use forged pistons. In fact, I'd be willing to submit that most of them do NOT use forged pistons. Anyone know?

 

I'm no expert or try to be, but I've been around boosted engines for a while.

I've seen both pistons and they have about the same ringland thickness. If 1BadBrd doesn't want to go into the engine just yet, there shouldn't be a need to if he lowers the CR to the 9:1 range. Dropping 1.5 compression points takes alot of pressure off the pistons, even if you do put a *little* boost through it. 6-7#s on a 10.5:1 setup, as we all have seen and heard, is pushing it a little too much. Some last a couple thousand, others go tens of thousands problem free. The same boost should be cake on a 9:1 engine, IMO.

 

Well you have to retard so much timing the gain of 6lbs would be less than just runing a good NAed setup. If you spend 3k on a blower, 2k on heads, $xxxx on other parts why slack on a set of pistons its just half a$$ed. With the power he would be making he better think about saving money for a tranny and rear instead of a time bomb motor. Sorry but 400bucks is not worth all the time.

 

I'm not sure where you're going with this. 1BadBrd's first post:

I thought about getting AFR heads with bigger combution chamber, that would lower my CR. Don't know what CR is best, but somewere around 8.5-9.5

I was thinking of Procharger P1-sc or D1-sc, with innercooler. More then likely P1sc.

Will this combo work until i have money to stroke out and really build a serious motor.

I was thinking of only 8 psi on the stock parts with lower CR.

How well would the stock bottom with lower CR hold up to 8psi?

OK, Just 8# of boost with stock parts. What would the life be like.

Then he later said this:

My whole idea behind this was to enjoy the blower while i saved money for the rebuild. I just wanted to see if i might get 50,000 miles out of this setup. It is not a daily driver, nor serious drag. Just wanted to spend some money have a seriour car to drive around it and save money for the rebuild.

He isn't building the shortblock yet. Apparently he fully intends for this to be a blower set-up. What's wrong with getting the blower and heads now and save for the stroker build later? He could do the tranny and rear now like you said, but that isn't what was asked here. Many people say do the shortblock first, but if he wants to do it this way, so be it. If it does blow, then he has a perfect excuse to do the build then.

 

That is simply not true. For 90,000 miles, on a stock LT1 bottom end, hypereutectic 10.4:1 and all, I ran 7 psi of intercooled ATI boost. Total mod cost was $3000. It would still be running now, but the crank snout got screwed up by unrelated problem. I was putting out ~425 rwhp, and 475 rwtq, and that was around 4500-5000 rpm, and that was through stock manifolds, intake, etc.

As long as you keep detonation under control, and don't get greedy with boost and try to go for 'just a little more', 9:1 will be very safe. And as for the $400 for new pistons, you have a lot more to buy than just the pistons. There's rings, bearings, hell, the gasket set is $200. And while you're in there, you might as well upgrade the rods, etc. It costs more than just a new set of pistons. Run it until it blows, then pay for the rebuild.

 

Well never mind then i was trying to give some advice i should have taken when i did my project. This advice can save money and time in the long run. So for the question no a stock short cant handle the type of power he will have with boost/big heads/../... Will it work yes will it last no.

 

I was pretty sure the turbo buicks have forged pistons, not cast. GM was more conservative back in the 80's. They put forged pistons in that motor for extra protection in case of some bad gas, etc. The first motor I built was a Buick V6, it was not the turbo motor though. Stuck it in a Vega.

With the low price of forged pistons these days, it would be stupid not to put them in. IMO, the same goes for the connecting rods. The crank seems to hold a lot of power though.

You can chance it and run hypereutectics, but if they break, you will never forgive yourself.

Forged pistons are recommended for anything over 400 horse.

Ed

 

They're hypers, trust me

They were conservative. If you ever see the dash of a turbo regal, you'll see a dummy light that says "POWER INJECTION." That was for the factory water injection system they almost put in it before production. Considering not many people out there had the sense to use it, they didn't go through with it.

Many of the guys out there are wireing their water/alky system to it so it lights when the pumps are on. Looks really cool.