Pistons in otherwise stock lower end

[speedy25]

Oil control on rings shows itself on accel. If it was your rings you would be leaving a cloud at every traffic light. A leakdown test will show ring condition better than anything else. Decel smoking is vacuum related. Since you put new heads on it shouldnt be VSS, and you have experimented with the PCV system. There is still something wrong. Keep at it. You'll figure it out.

-SP

[TurboSinceBirth]

I have a 2nd gen 4-bolt shortblock if you need anything out of let me know. I also have some 2nd gen heads too. It never hurts to have a motor to build so there's less downtime on the car if the motor in the car needs work. I would suggest running some sort of a PCV system to see if it still smokes. I would recommend a set of Krank vents. They work well. All of the PCV valves autopart stores sell are backwards so they don't work at all when you install them. OEM is the way to go.

[green-lantern]

Those compression numbers look pretty good. I'd hate for you to rebuild for no reason.

Oil control on rings shows itself on accel. If it was your rings you would be leaving a cloud at every traffic light. A leakdown test will show ring condition better than anything else. Decel smoking is vacuum related. Since you put new heads on it shouldnt be VSS, and you have experimented with the PCV system. There is still something wrong. Keep at it. You'll figure it out.

-SP

I agree with speedy, leak down test should be next before tearing down. I got to wonder about your oil return lines also. If you didn't have any dark cylinders I'd think you're still burning oil from turbos.

[andyvr4]

Those compression numbers look pretty good. I'd hate for you to rebuild for no reason.

That's my problem as well I really don't want to tear the motor down with compression numbers like it's showing and the fact that the smoke really isn't even at the right times for an oil ring.

At the advice of you guys and Matt with dynamic racing (who definitely knows a thing or to about these cars) I think I'm going to try putting a set of krank vents on and seeing if they fix the problem.

The smoke definitely seems consistent with the turbo's return lines not getting the oil back to the pan (I've already checked the return lines and even pulled the pan to make sure there weren't any obstructions in it) so Matt's thinking was that maybe it just needed more vacuum in the krank case to help suck the oil back away from the turbo's.

I'll update this thread once I get the krank vents and let you know if anything changes!

[green-lantern]

OK, sounds good, just make sure you get a large Krank Vent on the rear. A place sent me two small ones and it made my problem worse because the rear vent couldn't relieve pressure quick enough.

It’s hard to believe that’s your problem since you were running open vents. Definitely worth a shot though.

[FastOldGuy]

To me it sounds like your turbos are the problem not the block.

[andyvr4]

To me it sounds like your turbos are the problem not the block.

The rear turbo's been rebuilt 3 times now though by Matt's machine shop! I'm fairly confident it's not bad, but I do think it's somehow relate to the oil return from it. I'm really hopeful from what he's said that the krank vents will completely fix the issues.

[AdamVR4]

Are you using stock oil feed lines? If they're aftermarket, perhaps they're too large?

Why have you had the rear turbo rebuilt 3 times? How many miles did you get on each rebuild?

The OEM rear return line is basically vertical -- unless it was physically clogged (which would be shocking), it's probably not the problem.

Just to be explicitly clear, while you've been testing, you've had all 4 inlet ports on the cam covers open to the atmosphere and it still smoked?

If the krank vents don't work (large in back, small at the lower intake manifold), I would suspect the valve stem seal installation on the rear head.

And for what it's worth, my krank vents do an amazing job creating vacuum at idle. My system is well sealed (nothing special, just good gaskets, RTV (the right stuff) and hose clamps where applicable)... When I remove the oil drain plug it barely flows until I remove the fill cap

[andyvr4]

Are you using stock oil feed lines? If they're aftermarket, perhaps they're too large?

They're stock

Why have you had the rear turbo rebuilt 3 times? How many miles did you get on each rebuild?

Matt and me kept thinking that the smoke must be coming from a bad rebuild on the rear turbo (of which the first we're 99% was bad, it developed shaft play in almost no time, the second rebuild was partially my fault because I put a new adapter for the stock oil feed like on the turbo when it was rebuilt and this adapter was machined wrong causing a lot of restriction in the oil flow basically starving the turbo of oil, then this time we're 99% sure that it's correct, at least hopefully.

Just to be explicitly clear, while you've been testing, you've had all 4 inlet ports on the cam covers open to the atmosphere and it still smoked?

Yeap, all 4 of them have been opened

And for what it's worth, my krank vents do an amazing job creating vacuum at idle. My system is well sealed (nothing special, just good gaskets, RTV (the right stuff) and hose clamps where applicable)... When I remove the oil drain plug it barely flows until I remove the fill cap

I'm 99% sure after my testing that this is going to fix it. I just tried hooking the 2 inlet ports on the drivers side straight to one of the sources from the intake plenum and then blocked off the other to inlet ports on the passengers side completely and this all, but eliminated the smoke at idle!

Without any check valves I didn't want to try and drive the car though because of the risk of pressurizing the krank case, so I'll half to wait for the krank vents to 100% confirm that it's going to take care of the smoking.

[FastOldGuy]

Then your turbo itself is probably OK but its related to the turbo or vacuum IMHO.

I had the exact same issue. I had crank vents. I did a leak down and mine was OK. My turbos had very low miles on it. Turned out it was the rear turbo.