KA Pressure in head, heavy smoke from exhaust

[Hoffman5982]

Hey guys, I'm having a weird issue.

The motor setup is an s13 KADE. It is freshly rebuilt with Ross 8.5:1 pistons, eagle rods, fresh bearings, etc. The block was bored over and the rings were filed to Ross's spec. I have put maybe 100 miles on it and it drives great, but last night it started smoking heavily. It's very clearly oil that I smell. Keep in mind I did do some break in pulls, but due to a slipping clutch I don't think the motor has seen more than 4psi, it has mostly been cruising around in traffic. My PCV valve is setup with the pcv and valve cover vent both running to a catch can, and then a hose from the catch can running to the pre-turbo intake with an air/oil separator in line. I am also using an s13 SR pcv in place of the stock one since they are known to leak. The head is all stock. I had bent the valves when my timing chain guide broke so I put the valves from my spare s14 head into it. When I did this I relapped them well and pushed supertech valve stem seals on. I also feel it is important to note that the motor feels good while driving. The AFR's are around 14.7 while cruising and it isn't sluggish by any means. The coolant temp sits right around 165F. I haven't driven the car today but last night I only saw smoke at idle and decel. While driving there was no smoke.

Today I was messing with it, and after it was running for a few minutes I took the oil cap off. There was a burst of air that came out, similar to if you unplug the hose from an air compressor, but not that kind of pressure if that makes sense. I noticed that if I put it back in and pulled it right back off it didn't do it, but if I left it on for a minute pressure had built back up. So I'm suspecting it's something in the pcv system. To avoid oil slinging out on to the turbo manifold, I pulled the hose off the valve cover port. I noticed that when I had this off the smoke pretty much went away at the exhaust. There was also constant air coming from the port, and if I plugged it a little smoke would come from the hose I had taken off.

I know the first thing anyone is going to say is rings. While I'm sure anything is possible, I don't think that's the case. My first thought was a valve seal didn't get put in right, but after finding that there's constant pressure in the head, I don't suspect that. I'm going to start by putting in a new pcv valve. From there, I'm looking for suggestions. I really don't want to blow this freshly built motor up. My savings is already struggling.

[hanzbrady]

Why not eliminate the PCV and vent the catch can to the atmosphere? It sounds like you're pressurizing the crankcase which will cause blow by. Here's my catch can setup on my SR for reference.

https://i.imgur.com/H7IE1qyl.jpg

[Hoffman5982]

I previously had it with the pcv and valve cover to catch can, and had the can vented. Everyone told me this was wrong

[KAT-PWR]

You're doing something wrong. The KA valve cover shouldn't have the sr valve cover pcv in it. It should be ran to a vented can.

What did you do with the PCV valve on the timing cover? Lower passenger side of engine. What did you do with the factory pcv tree that runs into the runners?

To test run a hose from the pcv and valve covers into a big jug with the top open (like a Gatorade 2L bottle)

Is your catch can full of oil? What about the turbo intake?

Link to the catch can you're using? What size hoses?

[hanzbrady]

I previously had it with the pcv and valve cover to catch can, and had the can vented. Everyone told me this was wrong

It's the way it's done on every race car I work on which is more than average lol. My SR also doesn't have a PCV that just a straight nipple.

The only stuff that finds its way into the can is condensed water vapor, fuel vapor and a little bit of oil.

But this way my car doesn't smoke and also doesn't have all of that junk ending up in the combustion chamber.

[Hoffman5982]

You're doing something wrong. The KA valve cover shouldn't have the sr valve cover pcv in it. It should be ran to a vented can.

What did you do with the PCV valve on the timing cover? Lower passenger side of engine. What did you do with the factory pcv tree that runs into the runners?

To test run a hose from the pcv and valve covers into a big jug with the top open (like a Gatorade 2L bottle)

Is your catch can full of oil? What about the turbo intake?


Sorry, I wasn't clear. I took the SR pcv valve and put it in place of the stock one on the timing cover. The valve cover just has the straight nipple on the valve cover which is run to the catch can. The runner ports are capped off. The catch can is not full of oil.


It's the way it's done on every race car I work on which is more than average lol. My SR also doesn't have a PCV that just a straight nipple.

The only stuff that finds its way into the can is condensed water vapor, fuel vapor and a little bit of oil.

But this way my car doesn't smoke and also doesn't have all of that junk ending up in the combustion chamber.

See that's how I had mine. I did a lot of reading and everyone said the best way is to have the line running to the preturbo so that a vacuum is created to actually pull the vapors from the pcv. And with the air/oil separator oil won't make its way back into the intake. Should I just go back to my old setup? I still don't understand why there's pressure in the head like there is, or am I just wrong and that's normal?

[KAT-PWR]

In the KA the pcv check valve is in the fitting that threads into the pcv box which bolts to the valve cover.
Buy a 3/8npt straight fitting from Napa or the like and run that to catch can.
If your valve cover pops when taking oil cap off something isnt right as in the whole crank case is sealed.

Try running both PCV and valve cover to an alternate place like I stated with the Gatorade jug. With both ports in the open jug there should be PLENTY of hose width to evacuate any amount of pressure.

[Hoffman5982]

Ok so I vented the catch can and ran the valve cover to its own temporary jug and took it for a drive. The smoke has now gone away. I did only 3 or 4 small pulls and its running fine. Checked and no oil has shot out, only a little bit of condensation. So I think I'm just going to watch it for the next few weeks and keep driving through the break in

[tuzzio]

On my KA I ran the VC and PCV to a vented catch can with NO vaccuum pressure to it for 2 years with 0 issues. While I'm sure it helps pull crank case pressure out, have you ever started the car and put your finger over the pcv or valve cover breather? There is no fuckin way that thing has an issue escaping crank case pressure.

[240sxScores]

I have straight nipples to replace the stock KA24 PCV fitting that are the correct BSPT thread pitch. I'd sell you one if theres any interest.

[mewantkouki]

Pretty sure the large fitting on the valve cover is designed to suck fresh air into the crank case and the pcv valve & tree that runs to the intake manifold (stock) is designed to pull negative pressure and oily crap through the breather / separator box and be burnt out through the engine. So under boost I would run that line to a catch can under vacuum. (block) and have the valve cover breather connected to a separate catch can (atmospherically vented) with no vacuum source on it.

[Hoffman5982]

Pretty sure the large fitting on the valve cover is designed to suck fresh air into the crank case and the pcv valve & tree that runs to the intake manifold (stock) is designed to pull negative pressure and oily crap through the breather / separator box and be burnt out through the engine. So under boost I would run that line to a catch can under vacuum. (block) and have the valve cover breather connected to a separate catch can (atmospherically vented) with no vacuum source on it.

Well I hope it's not supposed to be sucking because mine is definitely blowing air. It's connected to the air intake on an na setup so I would think that pulls a vacuum on it.

It seems I still have smoke. Definitely not as much as it was as I can never see it(I do smell oil from time to time though), but my friend was behind me and said it was definitely smoking. The car runs great though. Not sure why a freshly rebuilt motor would have this much blowby, but I'm just going to rock it I guess. Maybe the rings haven't fully seated(I've put maybe 600 miles on it). I gapped the rings to Ross's specs, I believe .019 on the top rings and .021 on the second ring. Made sure everything was oriented correctly and so on. I guess we'll find out if it blows up again at this next drift event lol

[Ilya]

The valve cover definitely sucks air in, that's why it's pre-throttle but post MAFS, this way the air the engine sucks in is metered.

The KA pvc valve is only open during mild cruising and the engine vacuum sucks the air out into the manifold to be burned again.

With the turbo set up, ideally you would run a 3/8 barb from pvc box to oil catch can, then catch can to either pre-turbo(the vacuum created pre turbo should help pull out vapors) or open to atmosphere. The valve cover should run to a separate pre-turbo port so it sucks in metered air or open to atmosphere if in a pinch.

Since you have valve cover and cranck case connected via catch can, you may be pressurizing your valve cover especially if the SR pvc valve is being used.