Ok I blew another engine last night...bad juju. Wierd thing is I was only pushing 2psi! (only about 1000 on this set of rings, so I didn't want to screw them up). So I pull off my turbo pipes and I find a TON of oil in my intake. Not just a bit on the intake, but a TON like it was puddled up on my throttle bodie. I thought at first, bad pvc valve. But It is fine, Next thought is...blown turbo seals. I have no way to prove this, but I am suspcious. I know I have a blown ring land, but what the hell? Stock piston's can only hold up to 2 psi? So if I was getting oil from the turbo in the intake. Could the oil from the turbo break the ring land? The car never smoked, until the ring land broke. This is totally fucked up.
Here were my conditions
Fuel Pressure @ 40 idle.
a/f never left .96-.98
one range colder plugs
and boost only set at 2 psi MAX!

WTF and I doing wrong here? I am tired of rebuilding engines. Tired of this car breaking every 1000 miles or so..

Must have been a bad piston. Why are you rebuilding with stock parts anyway. Throw in some JE's and some eagle rods and you wont break any ring lands anymore. And dont feel so bad I have blown a couple engines my self.

are you checking the ring gap on ALL rings? The rings on the bottom are scraper rings still need to be within spec. That could be your problem. I'm gonna guess that the ring gap clearence was too tight and under that little bit of pressure it broke the land. Make sure that you put the rings inside the cylinder first w/o a piston to be sure that they don't need to be filed.

Wish I could afford to put in some better equipment. But till this winter when I save up enough money. This will have to do......almost ready to pull the piston's now, but it is break time...and time for some lunch. Im gonna set it at 0 boost this time and just run with it like that for the winter. Next spring my plan is to rebuld with forged internal's.

If you blew the motor at 2 psi, then detonation did it, not running 2 psi. Our stock pistons can handle a lot of boost, they just cant handle detonation very well. If you were driving around with a cracked piston ring landing, then oil may have been getting into the cumbustion chamber, which that alone will promote detonation if the oil is great enough. Do you have your breather line off of the valvecover going into the air filter intake? If yes, then all of that blowby from the broken piston is forcing pressure and oil out that line, and into the intake pipes. I would never drive much or very far with broken piston ring lands. I'd be willing to bet your piston is in very bad shape. You need to look into why you are getting detonation also. I'm sure the oil that was getting by the already broken piston is what caused more detonation and prob did even more damage to it. Add a little boost pressure to that, and kaboom.

Ok edit: are you saying you were driving with a blow ring land, or thats what you think happened? Oh, and you can break forged pistons just as easily as the stock ones, just they are a bit stronger and can resist a little more detonation.

dont wanna sound like a ass, but maybe you should have it built by someone who knows alot more then you next time you rebuild so maybe it will last you a bit longer. not tring to be a ass but trying to let you drive your car a bit more.. i hate to see people without there car due to little things not done right...
good luck

Michael 99gs
HRC Stage 2
Stage 3 process begins anyone got a 420a block thats not spun/head for sale?

http://www.dreamwater.net/purplebeast

No offence taken at all, but I do know how to rebuild this thing. Not even a mechanic would have been able to prevent this problem.
And Yes I had to drive quite a few miles after the ring land broke. So your probly right about the oil being in the intake.
So I have the engine completly apart. And I have 3 bad pistons. I dont' know why. My only reasoning is that, the three that broke are the originals with 100+K on them, The one that survived is one I bought from another member.
I am looking into a new fuel setup, This is most likey the reason that it blew.
I alway check my FPR about once a week to make sure that it is still sitting at 40psi at idle. I have never had a problem with my cartech unit. I am going to have to look at how I have it set up, mabey I have it connected wrong....I'm going to post a thread about it later today.

Did you ever check what your fuel pressure was under boost? How about your egt's? Running the stock pistons that had 100,000+ miles on them may not have been too good. Previous detonation events on the other motors may have weakened them, and could have put very small fractures in them that you couldnt have even seen. This worries me, as i know i detonated pretty good at times on my "good" pistons. The little bit of boost, and possible light detonation you got could have done them in..just a theory anyway.. Oh, and ditch the Cartech, its too bitchy ;)

Can you get some pics of the pistons? What exactly happend to them? Broken ring lands?

fuel pressure under boost was about 80 psi. Im gonna try to load up some pics tonight.

holy shit dude! you were at 80psi of fuel with 2 psi of boost on the T-25??? Am i gettin that right? If so, then thats what caused your detonation for sure. Detonation can also be caused by a very very rich fuel mixture also. Once you get to about 10:1 air fuel ratio, and below, detonation can happen too. On a S16G turbo, 2 psi of boost on stock injectors needs about 65 psi of fuel. I wouldnt think you would need any more fuel than that for the airflow at 2 psi on the T-25,as it flows less air at each pound of boost than the 16g.Get rid of the cartach!!!! A SFMU will be money well spent. Trust me. Its so versitile and holds rock steady pressures.

alright then what should my fuel pressure be at for 2psi? Im gonna look for corbin's site and do some math I think.....