Here’s the deal I need some with an issue that is plauging my buddy's T/A to see if we have missed anything before tearing apart.

The build:

2002 T/A WS6 M6
Stock block bored to 3.905
Mahle Forged Pistons 4cc w/rings kit
Scat H-beam rods
COMP cam 233/239 .595 .603 113LSA
Stock crank balanced w/rotating assembly
Stock 241 heads sent to TSP stage 2.5 with 2.02 intake valves, 1.575 exhaust, PRC dual springs .675
7.40 push rods
LS7 lifters
Tunion upgrade completed
LS6 intake
85mm MAF GM
Ported throttle body
4.10 rear gear
TSP headers
LS7 clutch and flywheel

Started and drove car with lucus break-in oil to dyno to be tuned made 412 RWHP 389 TQ. Drove the car for probably 200 miles changed oil to VR1 10w-30 when getting on the freeway when shifting from 2-3 the rear main blew out smoke screening all car on the freeway. Thinking this was an install error taking the car to my buddy’s shop (who deals with mainly LS/LT cars we replaced the rear plate/seal. Filling it again back up with VR1 10w-30 only to blow it out again within moments of leaving the shop, this time pushing out the dipstick 3 inches. After Talking to engine builder he advised that bearing clearance was tight and to continue to run break-in oil for a while. Ran the car about 1000 more miles with AMSoil break-in oil. Changed oil out VR1 10w-30 this time changed out LS6 valley plate to stock PCV off the valve covers. Only to blow out rear main and dipstick again. At a loss we did leakdown and compression test. Results 150 P.S.I. average no obvious ringers, leakdown was 2% loss these test were done by a shop so I do not know the details. Called a rep of DRIVEN oils he advised of that changing oil brands could have had an effect advised running BR30 for 100 miles nonstop change oil using BR30 again run normal for 500 miles then we went to ls30 changed out rear plate again car felt great we took it to the track made 4 runs, then again 3 gear on the fifth pass blew out rear main shutting down the track for a while. Does this make any since that the car has absolutely no smoke out the exhaust and normal driving car runs great, even right after the incident it leaks very little and runs fine only seems to an issue when hanging up in the mid to upper rpm’s. I have seen a couple of threads but no results and all little different. Any advice or thoughts would help I’m down to tearing apart and checking everything over.

thanks

 

Are you 100% sure that the PCV system and PCV valve itself is operating normally? All the hoses plumbed to the correct ports? No blocked PCV lines?

I'd throw a breather on the valve cover for a few passes and see if the trouble continues.

Only other thought I have would be harmonics vibrating it off but I'd think you'd be throwing the main pulley seal off too.

 

Yes, triple checked and used all new parts. even have a LS3 style pressure relief oil cap on it. As for the breather that is a thought. Do you belive that is only masking a bigger issue?

 

We actually built the motor with hopes in using the ls2 pcv system. We ended upgoing back to the ls1 system figuring it some how we damaged the ls2 we also added a catch can to the ls1 pcs

 

I'd say that would be masking it, but if it keeps you from blowing out the seals until you figure it out then it might not be a bad idea.

The pressure build-up is coming from somewhere - either you have excessive blowby or the gases that are generated can't escape. Since you only have 2% leakdown it doesn't seem like it would be blowby, so I'd say there's probably something obstructing the vent path.

what does your pcv routing look like, is it the stock configuration? any catch cans being used?

Just saw this. Remove the catch can and see if the problem goes away. If it does then you found your restriction

 

Good call. When we switched back to thels1 pcv we just installed the catch can cause everyone post you read there suppose to help.. I will update after we try

 

stock configuration with catch can before PCV. As KLO29 said we will remove catch can and check again. will update with results.

 

How much piston clearance do you have? If its blowing out the rear main you have serious blowby. ?The LS6 pcv system isn't gonna help that a bit. !st thing I'd do is pull the engine and look at the pistons, something is way wrong with them.
Another thing you could do is plumb a 0-30 pressure gauge into the dip stick then take it for a ride.

I personally don't believe 2% leak down......................in some ones pipe dreams maybe.

 

Yes, pulling the engine very soon. It did it with/without LS6 valley plate, with/without catch can. I guess that last resort. Side note as I was talking to the shop this is the third engine build that Mahle pistons were used and all three are having simalar issues, same builder the engines that Wiseco pistons were used no issues. None the less we will be update with findings of teardown. Thanks for the help.

 

Check the piston clearance yourself! Machine rookies are famous for doing stupid things like thinking when the piston clearance calls for 3 thous they think that means 3 all around the piston. It actually means 1.5 thpus around the piston. Easy way to check when you get the heads off use a set of feeler gauges to rough check it. See if the pistons rock in the bores. Good Luck.

 

Were the bores cut with a torque plate?

 

Torque plates were not used. Never been used on any ls motor he has built

 

We have all questions into the builder/machinist will update when answered. Great knowlege here, things I would hope a great builder would know.

 

The pressure comes strictly from piston blow-by. That means either there is a ton of blow-by which should also be burning oil or the PVC is NOT plumbed right. Whoever told you about bearing clearances has me scratching my head. They should be the correct clearance and not change over the engine's life. The rings are pretty much the only thing that needs breaking in and hopefully it was done right. Post up some pictures of your PCV routing.

 

This is a problem.

 

I agree but I don't think that alone will cause this much blow by.

 

Top rings installed upside down? gapped improperly?

 

We are going to tear into the PCV system for a final test. We are going to check vacuum and make sure the baffles in the valve covers are free flowing. We will call this the last quadruple check before we dig into the motor.

The engine builder didnt use the torque plates since it wasn't a massive bore.

 

Put a vacuum pump on it .

 

You suggesting I put a permanent vacuum pump onto the PCV system? If so I had purchased a gm smog pump as well as a harness from racetronix to make a home made vacuum pump for when at the track.

We scratch our heads every day cause we start talking ring issue then realize there isn't any oil being burned through the exhaust.. Im not much of a gear head but have learned alot diving into a Motor build head first.