[Bruce1223]

Hi, I'm fairly new to the site and was hoping someone could answer a question for me. I've got a 400 in my '67 firebird with around 3000 miles since a complete rebuild. Whenever I'm driving the car and really mash the throttle I can immediatly smell a hot oil smell. The engine has no leaks and uses no oil. Could someone explain to me what might be happening to create this smell. Thanks, Bruce

[WDCreech]

You probably have oil leaking from the valve covers onto the hot exhaust manifolds or headers.

[Ryche400]

Are you running a pcv valve? If not, it could be causing too much crank case pressure, and is escaping through the breathers. Just a thought..

[Bruce1223]

Thanks, I hadn't thought about the PCV valve. I'll have to check it to make sure it hasn't gotten plugged.

If the valve covers were leaking onto the EM, wouldn't you smell it all the time rather than just under hard acceleration. Or does the oil get splashed around under the valve cover more when you accelerate hard. FWIW I haven't noticed much leakage from the valve cover gaskets.

Thanks, Bruce

[Zombi]

I've got the same car, engine and miles and I've noticed the same thing. I also have no oil leaks and I've checked my PCV. I switched from Castrol 10W-30 to Rotella 15W-40 with no change. I've had people follow me and there is no smoke in the exhaust when it happens. I ran a compression test and everything looked perfect.

So I've decided not to worry about it anymore.

[Armadillo]

I have the same thing happening and I have found that the oil is coming out of my valve cover breathers. I have the EDL elites and there isn't a baffle on the breather hole. I will either get breathers with a collection hose or a baffle.

Tom

[kyle_blake]

You know what I found , is the oil pressure line coming off the oil filter housing may have a leak at the fitting.

Mine did, and slowly dripped down on header and such. Most lines route back through firewall to gauge around drivers seat area or center console.

Something to think about.

[Bruce1223]

Thanks for all the replies. The valve cover breather on my engine appears to be pretty old. Do these breathers break down after awhile so that they don't do as good of a job stopping that oil vapor from coming through? I'll check the filter housing area as well, but the breather idea sounds most probable to me right now. Thanks, Bruce

[uneasyrider]

Originally Posted by Armadillo

I have the same thing happening and I have found that the oil is coming out of my valve cover breathers. I have the EDL elites and there isn't a baffle on the breather hole. I will either get breathers with a collection hose or a baffle.

Tom

Ditto. About the same miles as the others above. Doesn't smoke or burn but comes out of the breathers under hard throttle. NP, normal and I agree with Armadillo on the solution but I do have a baffle but it doesn't seem to stop it. It's not oppressive but there is a hint of oil now and then. I see it as all part of the hot rod game, the smell of the hot headers, a little unburnt fuel, a hint oil, it's like potpourri for hot rodders. I bet I could market it and make a mint! I would feel a bit cheated if I didn't have some kind of engine fluid smell comeing from under the hood. lol How about when you're idling around in too tall a gear so you can really hear the cam and she starts to load up a bit and you get a bit of raw fuel smell and then you have an excuse to whip the throttle and "clear" the engine.

[chiphead]

Check to make sure the oil filter gasket isn't leaking. My car will drip a little past the oil filter's O-ring under high oil pressure conditions. Keeps the Hookers lubed on that side, LOL.

[TransAm525]

Unless you have a closed system style breather element (with the breather filter in the air cleaner housing) you will have crankcase pressure at WOT blowing oil out the valve cover breather. At WOT, there is no vacuum, making the PCV valve useless. Without the PCV valve creating vacuum in the crankcase, the pressure builds and blows oil vapor out any opening (i.e. the breather). A properly plumbed engine should have a PCV valve in one valve cover (or the valley pan) going to a combined vacuum source (i.e. rear of carb) and a breather tube from the other valve cover going to the air cleaner housing with a respective breather filter. This will allow the oil vapor to be sucked down the carb at WOT and burn the oil vapor/fumes, rather than spraying all over the valve cover.

[Armadillo]

My PCV valve is in the valley pan and plumbed into the carb and it is still doing it.

Tom

[TransAm525]

But where is the breather source? There should be a fresh air source into the engine (the breather). Are you using an aftermarket valve cover breather or are you using an air cleaner mounted breather?

[Bruce1223]

I've got the PCV valve plumbed to the valley pan and the intake manifold. And, I've got a valve cover breather cap. I don't have any leakage to speak of around the oil filter area. It must be coming out of the breather cap. I was under the impression that the breather caps were stock for '67s. Can anyone answer this for sure? Maybe it is just a condition that will exist with that style of a setup.

What would happen if you put a air tight cap on the valve cover and eliminated the breather? Probably nothing good, huh?

[Armadillo]

B3,

I had a 67 Tempest (80-85 I think) with a 389 3-2 and it had one valve cover with a cap and the other valve cover didn't have a hole for a breather. I had a high pressure pump and was blowing valve cover and oil pan gaskets. So if you do not let the pressure go somewhere it will get to your gaskets. I have breathers in both my valve covers and would rather it blow a little oil there instead of blowing the gaskets out.

Tom

[TransAm525]

Your setup is correct for 67, however GM later changed the design to the closed breather system due to the very same reasons you are experiencing, and for emissions reasons. The later design has a breather element in the air filter housing, and a tube running to the valve cover. When at WOT, the closed system allows all the oil vapor to just enter the carb, so there is no oil mist on the valve covers and the driver wouldn't smell oil at WOT. To remove the problem, you can go to a sealed air filter housing with the built-in breather design, or purchase some aftermaket valve covers with better oil baffles for prevent the oil from exiting the breather. What ever you do, don't replace the breather with a plain cap. The breather is the crankcase's fresh air source to replace the air the PCV valve is sucking out.

[motman]

this is what i found. on the older cast intakes the pcv valve fitting on the intake is very long.thus almost all the time in a vacume even at wot. if the brass pcv valve fitting is deep into intake runners there will always be some kind of draw. just like plumming for a draw from headers...just smaller