I regularly drive my truck on the highway at 70-80mph. With a 3spd, 4.88’s, and 37’s, I’m spinning between 3250-4000rpm’s. Problem is the motor starts breathing oil from the passenger valve cover breather at those high sustained rpm’s. Drivers valve cover has the pcv valve and is going into the carb. I could throw a catch can on it but don’t think that’s really going to solve the problem. Any thoughts outside of getting an OD (which is next years goal) or slowing down?
CK5
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PCV//Breathing Thoughts
- Thread starter centexk5
- Start date
OK, I'm turkey hunting, and not quite in my right mind........
But something about this just seems wrong.
The abbreviation "PCV" stands for Positive Crankcase Ventilation. In other words, the engine is supposed to pull a vacuum on the crankcase through that valve which sucks air in from the other valve cover through the breather. A lot of those used a small filter inside the big filter housing to source the air, and some just put a hole inside the big filter for the air. Either way, there should not be anything coming out of that hose. Air should be going in.
If you have oil coming out, then you either have a massive amount of blow-by that is pressurizing the crankcase beyond the ability of the PCV valve to relieve it, or the PCV valve and/or hose is clogged.
At least, I think so.........Heading to bed now.....
But something about this just seems wrong.
The abbreviation "PCV" stands for Positive Crankcase Ventilation. In other words, the engine is supposed to pull a vacuum on the crankcase through that valve which sucks air in from the other valve cover through the breather. A lot of those used a small filter inside the big filter housing to source the air, and some just put a hole inside the big filter for the air. Either way, there should not be anything coming out of that hose. Air should be going in.
If you have oil coming out, then you either have a massive amount of blow-by that is pressurizing the crankcase beyond the ability of the PCV valve to relieve it, or the PCV valve and/or hose is clogged.
At least, I think so.........Heading to bed now.....
It’s not coming from the hose on the vac side. It’s coming from the breather on the intake side.
Yes old engine. They are baffled covers and if by open you mean no media to capture oil then yes. They are also a gigantic pain in the ass to fill the engine with oil.
I think what @Fordum was trying to say is the the PCV on left valve cover can't keep up with the blow by at those speeds, maybe be cause the hose is soft and collapsed, or slugged up, possible even the pcv valve itself is slugged.
What is in the right valve cover a filter? Hose to air cleaner assembly ?
Also at those rpm the throttle is open farther than normal cruise, reducing the vacuum available at the PCV valve. So having good open hose and valve would be critical
What is in the right valve cover a filter? Hose to air cleaner assembly ?
Also at those rpm the throttle is open farther than normal cruise, reducing the vacuum available at the PCV valve. So having good open hose and valve would be critical
Passenger cover has just a filter on it. Driver cover has a hose from carb to the pcv valve.
Looks pretty good, inspect the hose for soft spots. Keep the filter clean. May be your motor is tired and letting a lot of gas escape, we all have that issue as we age 
After market baffle issues is the reason i am back to stock Valve covers. blow by and filling as you mentioned
I have no idea how old the motor is. The PO said it had been rebuilt in the past couple of years. 60 over bore with an rv cam. Oil pressure is crap though. 1-2psi hot and 25-30psi going down the highway. It’s one of the reasons I’m building another engine.
Burt4x4
1 Ton First Gen
Back in the day my ole 350 had some blowby that allowed crankcase pressure to rise and some oil would occasionally piss out from the front seal and the wind would blow it onto the headers making a smoky adventure and oil consumption.
On the way back to Cali from Moab 2002 (not towing, driving the K5) it got real bad.
The fix = Add a Second PCV to the other side valve cover. Used a T to join the hoses at the carb and split to both valve covers... now we go positive ventilation on both sides... no more oil pissing issues going down the highway
Try it, could be a cheep fix for now.. eventually I pulled the ole 350 and shoehorned a 454 in there
Oh yeah I use to get a random BOOOOM back fire too hahaa
Smokey on the highway =
On the way back to Cali from Moab 2002 (not towing, driving the K5) it got real bad.
The fix = Add a Second PCV to the other side valve cover. Used a T to join the hoses at the carb and split to both valve covers... now we go positive ventilation on both sides... no more oil pissing issues going down the highway
Try it, could be a cheep fix for now.. eventually I pulled the ole 350 and shoehorned a 454 in there
Oh yeah I use to get a random BOOOOM back fire too hahaa
Smokey on the highway =
Not a bad idea. I'll give that a try.
You can also try a fixed orifice style PCV valve. https://www.amazon.com/gp/product/B0010DW658/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 A lot of people recommend them for reducing oil consumption.
Interesting. Better than the little valve.
I'm trying one in my crew cab and the C10. Don't know if it'll make a difference or not, but I don't thing it can hurt anything.
If you want the ultimate solution, you can try this: http://mewagner.com/?p=444 I noticed quite a few people on the Edelbrock Pro-Flo 4 forum are running them.
If you want the ultimate solution, you can try this: http://mewagner.com/?p=444 I noticed quite a few people on the Edelbrock Pro-Flo 4 forum are running them.
Burt4x4
1 Ton First Gen
Never heard of such a ting = Cool, thanks
I just read about it for the first time a few weeks ago.
My older brother had a '66 K20 with a 292 six that had so much blowby you couldn't breathe in the cab at cruising speeds..
It had 4:56 gears and screamed going 60 mph down the road and the blowby was worst at high rpms..
The blowby would come out of the breather and coat everything in sight with oil eventually..once it got on the exhaust manifold it really stunk bad..
The PO had "rebuilt" the engine supposedly..he ran it about a year before pulling the engine to tear it down,it was found to have some piston rings installed upside down..!--no real other defects though..
He tried a few things like replacing the PVC valve with a new "stock" one,then tried some others off other engines that might have provided more suction,but that didn't help much..
He also tried running a hose from the breather fitting in the valve cover,to the radiator support,where it might have got some "ram air" effect at higher speeds,but that didn't pan out well either,it still spewed oil out of the breather and soaked the radiator,and a lot of the underhood area..(free rust proofing!)..
As a temporary "fix" he put a 3/4" heater hose from the valve cover breather fitting and ran it down under the firewall,back to about even with the transfer case and stuck a "bowtie" breather element from a V8 air cleaner in the end of the hose..
This did not cut down the amount of oil vapors coming out,but at least they got sucked towards the rear of the truck and you didn't suffocate driving it any more..
The truck ended up getting a 350 from my sisters rotted out '71 Caprice station wagon that ran perfectly instead of the 292 going back in--he claimed it plowed better with the six though..
It had 4:56 gears and screamed going 60 mph down the road and the blowby was worst at high rpms..
The blowby would come out of the breather and coat everything in sight with oil eventually..once it got on the exhaust manifold it really stunk bad..
The PO had "rebuilt" the engine supposedly..he ran it about a year before pulling the engine to tear it down,it was found to have some piston rings installed upside down..!--no real other defects though..
He tried a few things like replacing the PVC valve with a new "stock" one,then tried some others off other engines that might have provided more suction,but that didn't help much..
He also tried running a hose from the breather fitting in the valve cover,to the radiator support,where it might have got some "ram air" effect at higher speeds,but that didn't pan out well either,it still spewed oil out of the breather and soaked the radiator,and a lot of the underhood area..(free rust proofing!)..
As a temporary "fix" he put a 3/4" heater hose from the valve cover breather fitting and ran it down under the firewall,back to about even with the transfer case and stuck a "bowtie" breather element from a V8 air cleaner in the end of the hose..
This did not cut down the amount of oil vapors coming out,but at least they got sucked towards the rear of the truck and you didn't suffocate driving it any more..
The truck ended up getting a 350 from my sisters rotted out '71 Caprice station wagon that ran perfectly instead of the 292 going back in--he claimed it plowed better with the six though..
Mine is definitely not that bad. Only happens under high rpm.
Make sure you when add the second pcv valve to have filtered air inlet to the crank case. Other wise you suck air and dirt past the seals.
