Zach79Z

iTrader: (21)

Installed a catch can a couple weeks ago on my car after we rebuilt my motor. The motor has about 3000 miles on a complete rebuild. At about 2500 we noticed it smoking at start up. Also noticed a BIG amount of oil blowing into the intake. At the time we didnt really have a good routing for the PCV System so we used the catch can as a way to route it. Ran both the rear PCV exits on the valve covers into one, into the ctahc can, and into the intake, and blocked the front exit on the passenger side valve cover. Well the smoking has stopped. Car runs great. Just wondering how much oil should the catch can be actually catching? Drove the car on a 250 mile round trip to a carshow. Emptied the can the night before and there wasnt much. After i got home there was about (best way to measure it) 5 or 6 antifreeze jug lids full of oil. Sorry for the childish measuring system just only way to easily describe it. That was sunday. Emptied the can today and there was about 2 lid fulls. after about 250 miles put on it from monday through today from driving back and fourth to work. Should i have this much blow by or is this normal? Or is there another problem?

Heres a quick rundown of the car.
Rebuilt Stock bottom end (new rings, bearings, honed block, polished crank)
Ported and milled ls6 oil pump
ported 241 heads
231 239 617 624 @111+4 cam
Ported Fast 92mm intake
Nick williams 92mm tb
ls7 lifters
ls2 timing chain
ls2 lifter trays

Talked to a couple people at the body shop i work at and they said they would think it was normal for a moddified car to have a little blow by. It just worries me. Thanks for any and all help

Quick99Si

iTrader: (27)

I don't think you're pushing high enough compression or hot enough combustion temps to warrant a significant amount of blowby that the shop was referring to. I could be wrong, but it definitely seems a lot more than normal unless you were rowing through the gears on your roadtrip or something.

Assuming that the block was assembled correctly, I would think that either the rings haven't seated properly or it's a valve guide/valve stem issue. I believe that the only real way to get to the bottom of it is to do a leakdown test... or run a ticker HM oil (as a last resort bandaid type fix)

Zach79Z

iTrader: (21)

Bout the whole time down we was doing between 70-85 mph. Didn't really beat on it any due to my gf being in the car with me. Wouldn't if it was a valve issue the car be burning oil instead of blowing it tho? In the next week or two were gunna try a leak down teat and see. I have noticed that when I get home from work (about a 20 mile drive) at idle the oil pressure stays around 35. Driving it's around 60. I currently run a 5w-30 non synthetic oil in it.

Quick99Si

iTrader: (27)

Bad valve guides or valve stem seals can also let combusion gases into the head and be construed as blowby. Usually when these go bad, you'll notice a puff of smoke upon startup after the car had been sitting for a while. That's not to say that bad oil control rings wouldn't exhibit similar symptons, which is why it's tough to say anything with certainty until a leakdown test is performed.

The best way (albeit still not 100%) to distinguish between bad rings vs bad valve seals (guides/stem) is usually *when* you throw out the most smoke. Bad valve seals will have you burning a lot of oil under vacuum (engine braking) and startup; rings will do it moreso under load.

Hopefully I'm wrong, this is the internet after all.

Zach79Z

iTrader: (21)

Weird thing is it doesn't smoke at start up. It usually sits from Friday untill Monday without being started and won't smoke. It blew out smoke when I started it after a few seconds on Monday but it was like 30 degrees here.

Zach79Z

iTrader: (21)

Checked my catch can yesterday and emptied it into the same container with th other bit I'd oil I've gotten out of it. Checked the oil and I was half a quart low. I barely have enough oil in this container for maybe a 1/8th of a quart. I'm guessing it is the valves seals? Also looked at the exhaust at start up and it blew out a quick puff of smoke.

Steve Gunn

That's not an exit, it's an entry for fresh air and is absolutely necessary. Search pcv and catch can routing.