Help please - excessive oil from rocker covers

Oldskoolrob

Oldskoolrob

Active Member
Hi all,
Very disturbed to find an air filter full of oil after a drive. As a diagnostic I disconnected the PCV line and installed a breather (so breathers on both rocker covers, vent at rear of engine open with small filter) and after a short drive there's oil everywhere. I removed the filter from the small breather at the back in case it was blocked, so now there's NO vacuum at all and the engine is still spilling it's guts all over the engine bay. So to me this says there's excessive pressure in the crank-case? Which would mean what - a blown ring? Step one to diagnose is a compression test, yes? So tired of problems with this car..... :(

NB, only spilling out of the even bank, and out of the breather at the back which has a hose attached, about as long as the tranny dipstick. One bank might mean a blocked return gallery perhaps?
 
Before phoning up the junk yard why not try a couple of things.
As you know the rear breather should be clear, so connect a pipe to the steel T and see if you can blow into the valley area.
Secondly see if the flame traps on the breather pipes coming from the rocker covers are clear, these must have no resistance at all. In fact best check all the breather pipes to the carbs are clear.
The heads have ample drain back along their length to let oil return into the valley area, so should not retain oil.
My money is on blocked flame traps.
 
Sorry, didn't mention it's a Holley conversion- I have no flame traps in place at the moment. Just breather filters on both rockers as I diagnose (I did have a line to the air filter but I'm removing components as a differential diagnosis). I know the rear breather isn't blocked - I could see it venting oil vapour on idle.....
What I did have was breather on odd bank, motorcycle filter on rear, and even bank plumbed inside the filter element.
 
OK got the picture.
Take off the oil filler cap at idle and see how much blow by you have coming out, if it is significant then yup something is amiss. I guess compression and leak down testing is the next step.
 
I would say a pulsing puff that you can feel on your hand is getting to be more than you want to see. I have had cars with a soft stream of blow by that still run OK.
The 3.5 original motor in my car burnt a lot of oil and was stinky and the blow by was quite a decent pulse from the opened filler hole.
There is going to be some, you will have to use judgement as to whether it is excessive.
 
Ok cheers. Maybe a catch can will hold off the inevitable. Fixing the P6 was supposed to be quick and easy...didn't turn out that way. May have to park it and go back to working on the Cortina.....*feeling despondent*
 
Well I had a look in the light today, 30 seconds after start up there's mist wafting out of the oil cap hole. Father in law (loooong time mechanic) agrees that it's way too much and a ring is the likely culprit. Going to book in for a leak-down test (I don't have the gear) so I know if it's only 1 cylinder. So, can you remove the sump while the engine is in? I'm hoping if it's just one cylinder I might be able to re-ring that pot in the car.....
 
Oldskoolrob said:
So, can you remove the sump while the engine is in? I'm hoping if it's just one cylinder I might be able to re-ring that pot in the car.....
Click to expand...

Yes, but if it's an auto you have to remove the exhaust downpipes. You can do all the rings with the block still in the car.
 
Leak-down test booked for monday. Is there anywhere the oil galleries are close enough to the cylinder in the head, that a failed head gasket could be the cause? If it's a cylinder, I'm not sure if I should try and just fix that pot or rebuild the whole bottom end...maybe that depends on if I find a broken ring? If it's a glazed bore the whole lot will have to come out. Realistically, this means the end of my Roving for quite a while, as she'll have to be parked up until I have the time/finances for such a big job. :(
 
So 'leak-down' has been moved to Friday because of 'stuff'. Next question, if I can identify one cylinder is the culprit and I can pull that cylinder with the engine in the car I can only fix it if it's the ring, right? I imagine even thinking of honing a glazed bore insitu is stupid, right? I guess I should also get the head checked for straightness if it comes off hey? Just thinking ahead......
Other option is shelve it, and in a few years time pull the engine for a complete re-do.....or whack a 350 Chev in. :eek:
 
You can re-ring one piston, but why would you? You can hone the bores before refitting. (When the piston is out)

In my experience the heads rearely warp, and mostly only need skimming if the head gasket has been blowing across areas for long periods. Remember that skimming one head only will cause head/inlet manifold alignment issues.
 
The engine when I bought it was reported to only be 30 000K after a full rebuild - which I believe due to a few things. Which is why this is a bit of a blow (pardon the pun). If I can get away with fixing one cylinder with the engine in the car it might happen before the end of the year. I want to 'mess' with it as little as possible because I'm no mechanic.....
 
Most are around 105-110psi but #4 and #6 are 84 and 92 respectively. I'm hoping there's an outside chance that a gasket failure has resulted in both dropping, and pressurising the valley or sump at the same time........These are on the drivers side, which is also the side leaking.
 
Just the head gasket blown between the two cylinders would be my guess so you may be lucky. I'd still replace both gaskets at the same time though...
 
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