Sorry for the loss Jetpilot...

 

crap - what were the build specs? No chance of a measurement error? jeeez - so what is the diagnosis given the relatively good compression #s? Did you hear where the leak is for 2 & 3? No coolant overflow issues, right? 2 and 3 are way apart - little chance of a hg problem. with compression good - leaky intake or exhaust valve?

 

This thread made me sad. Don't give up Jet...

Very informative posts. Makes me scared of built blocks.

 

No chance of measurment error. I did all the cylinders and then went back to check cylinders #3 and #2 and got the same readings as before. #2 and #3 are leaking from the rings. I could hear the air comming out of the drivers side breather and when I removed the oil cap I could feel a large amount of air comming out. I had the plenum off and stuck a hose into the intake runners of the cylinders to check the intake valve seal. They were quiet.

This is where my crankcase pressure problems are comming from.

I did have some coolant oveflow issues recently, but the coolant is clean with no contamination. I can't explain that.

 

Sorry to hear that Jet

 

So you just have to replace the rings on #2 and #3 pistons correct? Shouldnt be that big of a deal right?

 

If the rings collapsed then the pistons will likely be scuffed and have to be replaced and depending on the condition of the bore the block may need to be replaced or honed. It could be a bid deal.

 

wow this really sucks man...

 

track racing is expensive. i'm sure you will rebuild, upgrade and run 600+ hp.

 

Well, that sux... Sorry to hear...

A couple of thousand racing miles is quite a bit...

I'd replace all the rings... maybe throw the torque plates on the block and re-hone it a bit... see how straight the cylinders are...

 

It was no where near a couple thousand track miles on it. Maybe it had 90 laps at Sebring. That's only about 360 track mi. That was it. The rest were highway miles going to and from the track and back and forth to shops for work. The last 2 track day I only got about 20 laps each day due to this crankcase press issue. I will rebuild the motor to sell, but the motor will probably not go back into this car.

I have started to compile a parts list with prices which will be posted up shortly.

 

in for the list... again sad to hear.

 

D@mn.. sorry to hear that... I hope a minor ring replacement will fix the problem. Good luck!

 

Could a dry hotspot in the coolling jacket cause the coolant to rapidly vaporize when it touches it causing the coolant to turn to steam, expand, and fill up my overflow container causing coolant to blow out? Maybe that hotspot burned the rings? The coolant is clean and uncontaminated with oil carbon etc. Just a thought.

 

I would think the forged pistons are a lot stronger than that. You have Arias ED, right? I'm wondering if it's just not a headgasket issue -perhaps damaged by the same mechanism you note above. One of the theories behind running Evans NPG+ is to prevent such hotspots - haven't heard of a headgasket failure on Evans yet (fingers crossed). Maybe headgasket damage is allowing a path for air to escape between cylinders 2 and 3 only... I wonder if you can detect air coming out of cyl 2 when testing cyl 3? (and the reverse?)

 

Im really sorry to hear this. I dont drive my car hardly ever anymore, Id rather have a car that runs that I never drive than a broken Z I cant drive. Damn these cars when you push them hard...good luck. I also made a parts list at one point, I know the feeling.

 

^^^ +1 on that - I got to make the parts list as well, before the motor even made in into the car

You may be able to get by with some new rings and a block hone like fort suggested. Still, motor removal and disassembly isn't cheap......or fast.

 

Jet, put the car on a dyno and see how your power curve looks compared to your past run. Although the engine may be a little weak, rebuilding at this point may not be required. I guess what I am saying, is to use that engine to the max, and then rebuild. After all, it is mostly a race track car now. No sense in wasting those other 4 perfectly healthy cylinders. Just trying to see some bright side of things.

 

Throw some restore in there for the hell of it. Can't hurt anything. lol

 

Sharif has a good point. The motor may be a little on the weak side, but still might have some life left in it. I'm guessing the leakdwon was done on a cold motor, so at temperature the rings might seat a little better. It would be worth the effort to put a boost gauge on the crankcase and measure the pressure before throwing in the towel. A vacuum pump may be needed to help the situation, but knowing how bad it really is up front is imperative.

I have two friends that have run their engines for another year or so, with leakdown #'s in the mid 20's measured on a cold built motor with aftermarket rings & pistons. They didn't have the oil issues Jet is fighting though, they just experienced low hp numbers overall compared to similar setups with normal leakdown #'s.

I wouldn't necessarily give up on that motor yet, but do completely understand the frustration involved after all the money spent and time invested. Heavily modified cars are not always nice to their owners, at times they can seem down right vindictive.