KA24DET Problem "Oil on Piston Tops" HELP Please !!!!

[dwaynedman]

I have a problem with my KA24DET.... I have about 800 miles on a fresh rebuild with all forged internals and total seal rings. My friends have been telling me that I am blowing bluish smoke from my exhaust on deceleration. I told them that they are crazy, that it had to be from running rich under boost, then blowing unburnt gas on the decell. This weekend, I decided to check my plugs, and had some detonation on the electrodes. I then decided to look into the cylinders with a light, and to my suprise had a coating of fresh oil on the top of every piston. Is there a reason for this? Being a turbo application, is this possibly from crankcase pressure ?? I have my VC vented to atmosphere, but no other PCV work done.. everything else is stock config.

I can't see my oil rings being bad at 800miles, and have 150psi on every cylinder. Any input would be appreciated !! ThanksD

[480sx]

Sounds like valve seals.

[dwaynedman]

But they are brand new, is that possible after 800 miles on all 4 cylinders ? I am a mechanic by trade, and have never had that problem with valve stem seals before. Is it possible that I am getting crankcase pressure and blowing through the PCV to the intake ?? I think I will take the head off anyway just to check out the valves and see if anything is wet on the top end.

Also, I have never dealt with a low compression engine before, is 150 PSI per cylinder considered low @ 8.5-1, or should I still be around 160-170 like normal ??

Thanks D

[neverlift]

if your pcv is hooked up stock it may be the problem, try dumping the pcv to atmosphere and/or run your vc to the turbo inlet..good luck

[dwaynedman]

Is there a writeup somwhere on what I need to do to the PCV to dump it?? And do you mean run my Valve cover breather to the inlet side of the turbo between the MAF and the compressor housing ?? Thanks for the responses, I am now wondering how to alter the PCV when I dump it, so it dosen't get oil all over the place !

Thanks D


Modified by dwaynedman at 11:39 PM 8/30/2008

[480sx]

Idk i cant see a PCV system failure causing this. The stock oil separator does its job well and its never going to fail. The valve itself might fail, but even thats not going to cause oil to be sucked up into your combustion chamber.

If you want to check it though just completely disable your PCV system(just to test the theory out for a bit) and see if you still blow smoke.

[WDRacing]

If the PCV is bad and he is pressurizing his crankcase then when he's on boost. This could allow oil to enter the intake on decel when the engine is pulling tons of vacuum. There are extra one way check valves you can install with the PCV.

I'm working on a new setup that involves a GM smog pump and a oil/air separator that will vent the crankcase on boost.

If you aren't going to use an external system to vent the crankcase then I recommend running a line from the VC to a separator and then to the turbo inlet after the MAF. Use a free flowing separator, they are about $20 from Home Depot. Quite a few guys that run supercharged Mustangs have had luck with this setup.

Pull your intercooler piping apart and check for oil residue and let us know what you find.

WD

[Brandon93240]

I would definetly say valve seals or incorrect piston ring gap. Without getting to far in it pull you exhuast mani off and see what the stem of the exhaust valve looks like. If you see an oil ridge ring on the valve where it stops at full close into the guide its definetly the seals. An no your compression isn't low for those pistons. I'm in the 153-155 range with a conservative ring gap and 8.8 pistons.

[WDRacing]

The only reason I wouldn't think it was valve seals is because he has oil on ALL of the pistons. Unless they were all installed wrong they definitly aren't all going to go bad.

Like I said, before pulling the head, check the pcv valve, check the fmic piping for oil residue, look inside the compressor as well.

WD

[dwaynedman]

Well, I pulled off the Turbo this morning, no residue, but a lot of end shaft play for an 800 mile Precision turbo "Sucks" !! No residue in downpipe, intercooler piping, or anywhere near the Throttle Body. But there is some residue on some of the exhaust valves, but only on 1 & 3 cylinders. I still have a decent little puddle on the tops of 2 & 4 as well, so I'm starting to lean towards crankcase pressure. It makes more sense to me, especially with healthy oil squirters soaking the cylinders down. I still think I am going to tear the head off anyway, so I can check cylinder walls, and intake valves etc... all at the same time.

My buddy that just tore his engine down because of smoking, said that his compression was fine but oil rings were bad. I've never heard of that either... I would think that compression would have to be somewhat bad to let oil pass right ?? Thanks for all of the advice, I will keep you guys updated when I get the rest of the head off. Thanks D[IMG][/IMG]

[WDRacing]

Check this out to...it will assist with blowby on boost.

http://www.stealth316.com/2-krankvents.htm

[dwaynedman]

Thank you for the replies !! I just took off my intake manifold, and found small puddles of oil around the PCV tubing that meets the runners. Also found that 6 of 8 exhaust valves had oil around the tops of the stems. "but dont think that that is leading to oil on pistons" Very Minnimal" Also noted that there is quite alot of play "side to side" in #1 & #4 pistons, and walls look a little scraped! With all of that being said, and having it this far apart, I think I will pull the motor and take it to the machine shop for an oversizing. Then will follow up with WD's Krank Ventilation System.

Thank's All !D

[WDRacing]

Let me know before you install the whore again. I should be done researching all the info for the crankcase vent system by then. WAY cheaper then a belt driven vac pump man...

WD

[480sx]

GM made an electric vac pump from 94 - 96 on LT-1's. Im gona find a wrecked vette and see if i can snag one to mess with.

I still think my PCV system kicks *** though.. Three lines running to a catch can. Two from my valve cover, and one from the stock PCV valve. From the catch can to the pre turbo intake. Its already been battle tested and worked incredibly, i pulled a half pint of black gas with no oil out of my catch can when i had a cylinder running rich.

From the little research iv done i have gathered that you will actually see some gains by having your crank case under vacuum. The theory being is that it pulls the rings out against the cylinder walls as much as possible and increases the seal.

The only downsides i have seen so far is creating to much vacuum which can suck out oil(this can be avoided by using the stock oil separator). The other downside(this one seems far fetched..) is that to much vacuum could suck out the oil from the rod bearings.

The other common method used by drag guys is to use the exhaust/down pipe as a vac source.

Two good threads on PCV theory and setup.

http://www.dsmtalk.com/forums/...30210

http://forums.evolutionm.net/a....html

[kouki_hmongster]

Let me know before you install the whore again. I should be done researching all the info for the crankcase vent system by then. WAY cheaper then a belt driven vac pump man...

WD

Do you recommend using the krank vent? if you say that it should be fine then i'm ordering mine. i just dont want anything to go bad while breaking in my motor. breaking it in w/ turbo on but not planning to hit boost.

[WDRacing]

It's just another check valve that doesn't let the stock PCV leak under boost. So I definitly recommend one.

[kouki_hmongster]

cool thanks. hope to get mine very soon, btw should i also run a catch can from the valve cover breather to turbo inlet pipe? i called them up about krankvent and the guy told me that i wouldnt have to since theres the bigger check valve from the breather to turbo inlet pipe.

[WDRacing]

The check valve prevents air from traveling backwards into the valve cover when you're in boost. If the line goes from the VC to the pipe pre turbo you'll be fine. But yes, I would run a air/oil seperator for sure. Or else you'll be ingesting crap that's sucked out of the sump.

They are only like $20 from Home Depot.

WD