Oil Blowby
Thread Starter
Burning Brakes
Joined: Nov 2006
Posts: 893
Likes: 7
From: Orange Park Florida
Oil Blowby
I have been working with a minor oil blowby issue for some time. I've experimented with pcv routing, swapping sides on valve covers, etc to no avail. Today I removed the pcv valve and installed "breathers" on both valve covers, plugged the carb input, and started the engine. I immediately noticed small puffs of smoke coming from the right (passenger side) bank. The smoke is barely noticeable and it only comes from the right bank.
Does this sound like a ring issue, or, valve leaking?
Car is a 72 Stingray with a rebuilt 350 out of a 1973 vehicle, Engine codeV0620AJF- 1973 350, 155hp 2bbl. I don't know who built it and what has been done but it does run strong. It has 4bbl Qjet carb.
Any ideas?
Does this sound like a ring issue, or, valve leaking?
Car is a 72 Stingray with a rebuilt 350 out of a 1973 vehicle, Engine codeV0620AJF- 1973 350, 155hp 2bbl. I don't know who built it and what has been done but it does run strong. It has 4bbl Qjet carb.
Any ideas?
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
Blowby is a ring seal related issue. If it's not horrible you could just get a catch can (oil seperator) and put it between the PCV valve and the carb on the left side and it will catch much of the oil instead of reintroducing it in the intake. The best arrangement for the right side is to have it go into the air cleaner.
Vents are going to make a mess under your hood.
When using the PCV on the left the vent on the right becomes an intake for air into the crankcase. When you go WOT the vent on the right side is no longer going to be sucking and is going to be blowing. It would preferable to be venting into the air cleaner vs venting out onto the engine and under the hood.
Oil burning can be caused by worn out valve guide seals as well, but it sounds like you didn't see smoke until you removed the PCV system.
Vents are going to make a mess under your hood.
When using the PCV on the left the vent on the right becomes an intake for air into the crankcase. When you go WOT the vent on the right side is no longer going to be sucking and is going to be blowing. It would preferable to be venting into the air cleaner vs venting out onto the engine and under the hood.
Oil burning can be caused by worn out valve guide seals as well, but it sounds like you didn't see smoke until you removed the PCV system.
Team Owner
Joined: Sep 2006
Posts: 31,278
Likes: 4,372
From: Westminster Maryland
Hi Jim,
Might this help?
Here's a pretty simplified illustration that shows what happens to 'blow by' when the engine has an operating pcv valve and crankcase breather.
Since you have neither now, you're seeing the blow by.
Regards,
Alan
Might this help?
Here's a pretty simplified illustration that shows what happens to 'blow by' when the engine has an operating pcv valve and crankcase breather.
Since you have neither now, you're seeing the blow by.
Regards,
Alan
Thread Starter
Burning Brakes
Joined: Nov 2006
Posts: 893
Likes: 7
From: Orange Park Florida
I need to do more diagnosis here, and maybe check valve seals, etc.
Thanks
Melting Slicks
Joined: Feb 2006
Posts: 3,105
Likes: 96
From: Sunrise FL
I am having a similar issue. I think my problem is aftermarket valve covers that have PCV oil baffles, but they dont seem to help much.
Others have said that the part number of the valve (how much it actually sucks) can have a big effect too...
Others have said that the part number of the valve (how much it actually sucks) can have a big effect too...
Thread Starter
Burning Brakes
Joined: Nov 2006
Posts: 893
Likes: 7
From: Orange Park Florida
My engine is plumbed just like your diagram, with the exception of the filtered air intake - I was just using a valve cover filter. But I have noticed for some time that the filter would get dirty/oily in a short period.
I need to do more diagnosis here, and maybe check valve seals, etc.
Thanks
I need to do more diagnosis here, and maybe check valve seals, etc.
Thanks
Thanks..
Team Owner
Joined: Sep 2006
Posts: 31,278
Likes: 4,372
From: Westminster Maryland
Hi Jim,
Great!
Regards,
Alan
Does what side the pcv valve should be on depend on whether the crankshaft rotates clockwise or counter clockwise????
Great!
Regards,
Alan
Does what side the pcv valve should be on depend on whether the crankshaft rotates clockwise or counter clockwise????
Last edited by Alan 71; May 15, 2017 at 05:18 PM.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
None whatsoever. It has more to do with convention for that manufacturer than anything else. You have a Ford, you'll find the PCV on the passenger side valve cover. And unless this is one out of a dual-engine marine application, the norm is clockwise rotation.
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Race Director
Joined: Oct 2008
Posts: 19,227
Likes: 1,672
From: Long Island
Most PCV valves allow too much air flow as compared to the originals.
There are a few good articles on the PCV valves. I learned a lot on my 85 - worked engine that fouled the #7 plug but had good heads and rings. I ran Pontiac when younger and the PCV was taken from the CAM / LIFTER VALLEY via a hole behind / under the carb - less chance of fouling. Pontiac always has an air gap manifold as OEM.
After I restricted the PCV system the fouling stopped. I will eventually get a proper adjustable PCV valve ..
The PCV is just there to "capture oil vapors and unburnt gasses" from exiting the engine into the atmosphere. Sometimes they wind up sucking oil from the valve cover and foul the plugs.. The older engines exited the gasses to the rear of the engine via a tube pointed toward the ground. Not good for the air or following cars in the rain....
There are a few good articles on the PCV valves. I learned a lot on my 85 - worked engine that fouled the #7 plug but had good heads and rings. I ran Pontiac when younger and the PCV was taken from the CAM / LIFTER VALLEY via a hole behind / under the carb - less chance of fouling. Pontiac always has an air gap manifold as OEM.
After I restricted the PCV system the fouling stopped. I will eventually get a proper adjustable PCV valve ..
The PCV is just there to "capture oil vapors and unburnt gasses" from exiting the engine into the atmosphere. Sometimes they wind up sucking oil from the valve cover and foul the plugs.. The older engines exited the gasses to the rear of the engine via a tube pointed toward the ground. Not good for the air or following cars in the rain....
Last edited by BLUE1972; May 16, 2017 at 10:34 AM.