Smoke comming out of oil cap

[mike561]

I have those chrome aftermarket valve covers with a vented push-on oil cap, and sometimes i see smoke comming out the vents of the oil cap when the engine is hot, i suspect this is "blow by" from worn piston rings correct? i put some of the Lucas oil treatment in a while back and it took care of the problem when i had smoke out of the driver side tailpipe, maybe that will take care of this too til i can get it fixed correctly? the PCV valve is good btw

[j cAT]

Originally Posted by mike561

I have those chrome aftermarket valve covers with a vented push-on oil cap, and sometimes i see smoke comming out the vents of the oil cap when the engine is hot, i suspect this is "blow by" from worn piston rings correct? i put some of the Lucas oil treatment in a while back and it took care of the problem when i had smoke out of the driver side tailpipe, maybe that will take care of this too til i can get it fixed correctly? the PCV valve is good btw

you are not supposed to use a vented cap...the crankcase needs to be purged of blowby gases thru the PVC /crankcase venting..

with this set up you have,, you will suck this oil vapor into the air vents into your interior ..


a well worn engine creates excessive blowby gases ..rings/valves/crank bearing etc..basicly the oil temps rise and the oil vaporizes ...

[mike561]

I had a seald oil cap before and the valve covers started leaking, possibly too much pressure building up? I'll get another sealed cap if thats what it takes... whats the point of those vented caps then?

[Blue Bowtie]

Originally Posted by j cAT

you are not supposed to use a vented cap...the crankcase needs to be purged of blowby gases thru the PVC /crankcase venting..

with this set up you have,, you will suck this oil vapor into the air vents into your interior ..


a well worn engine creates excessive blowby gases ..rings/valves/crank bearing etc..basicly the oil temps rise and the oil vaporizes ...

What he said.

Get rid of the vented cap and reconnect the CCV to the air cleaner where it is supposed to be. If the CCV is routed correctly and the filter pad in the air cleaner is not plugged the crankcase should not develop pressure since it will vent into the air cleaner.

...if thats what it takes... whats the point of those vented caps then?

Those things are made to SELL, not to USE (just like most oil additives, etc.). Actually, in a blown or boosted engine they DO have a place, but it you don't have an Eaton blower or Garrett turbine feeding your intake, forget about it.

[j cAT]

Originally Posted by mike561

I had a seald oil cap before and the valve covers started leaking, possibly too much pressure building up? I'll get another sealed cap if thats what it takes... whats the point of those vented caps then?

make sure you have good vacuum to that PCV ....sometimes that line fails or the carb fitting gets carboned up...then crankcase pressures will create those leaks...with these carb engines it is this vacuum line that causes many engine idling/running issues ..


I have also seen these lines collapse,crack in one small area, loose fit on pcv/carb port etc....

[mike561]

I know what youre talking about, thing is i dont have the stock air cleaner housing anymore, i have a round k & n filter with just two chrome plates on the top and bottom. then i have the PCV valve comming out the pass. side valve cover with a hose that connects to the bottom front of the carb. then on the driver side is where i have the vented oil cap of course.

[Blue Bowtie]

The bottom plate of the filter probably has a knockout pre-punched to install a CCV tube fitting.

Frankly, it might be better to install the original air cleaner (or a junk yard donor) and ducting to pull cooler air from outside the engine compartment for more power production and mileage. You can install a polyester element (K&N) in the stock air cleaner if you like. The chrome open element air cleaners look pretty but don't do very well for providing cold air. A dual snorkel air cleaner from an '80s L69 from a Camaro or Monte would work great. You can also convert a stock single snorkel to a dual with a little work and an extra donor air cleaner.

[mike561]

there is a punchout in the chrome plate as you mention. if i were to go that method where would the pcv valve go then? i see what you mean by putting the factory air cleaner back with a k & n filter inside too which i may do.

[j cAT]

Originally Posted by mike561

there is a punchout in the chrome plate as you mention. if i were to go that method where would the pcv valve go then? i see what you mean by putting the factory air cleaner back with a k & n filter inside too which i may do.

on your vehicle I believe the crankcase filtered air enters the valve cover on the passenger side...then the pcv is mounted into the driverside valve cover and then this 3/8 vac hose connects to the carb base...this then causes fresh air to enter one valve cover and exit the other ...

the open type air filter support that you now have,, you would connect the passengerside air intake to the valve cover inside of the air filter in the filtrated air area, then this would be the source of the crankcase air on passenger side ..PCV does not change same as OEM ...

originally the air intake for the crankcase was mounted on the side of the enclosed air filterhousing ..the inside on the housing there was a small filter made to filter the warmed air inside of the air box....then a pipe connected this filtrated air into the passengerside valve cover..


after writting all this I realized you have the wrong valve covers ....they look real good but don't function ...this is why you have these crankcase pressure problems blowing out the oil through the gaskets...

[mike561]

yeah i forgot to mention i also have aftermarket chrome valve covers (the ones with only one hole on each side) when i bought the car three years ago it didnt have the original valve covers already

[j cAT]

Originally Posted by mike561

yeah i forgot to mention i also have aftermarket chrome valve covers (the ones with only one hole on each side) when i bought the car three years ago it didnt have the original valve covers already

if you find some OEM valve covers you will see that there are baffles inside of the covers where these crankcase vent componets are mounted..its not just a hole ...

[mike561]

oh ok, next time im at the salvage yard ill probably pickup the valve covers and air cleaner then