Since getting my engine re-built, I've had problems with oil coming out of the rocker cover breather (K&N style gauze filter, fitted to the filler hole), and PCV.
A Hi-Vol oil pump was fitted as part of the re-build. The rocker cover is the black finned Commodore style, but has no internal deflector plates like the old steel red motor ones.
I've fitted my own deflector plate to cover the PCV outlet, but I still get a lot of oil spraying out of the breather when the engine is revved.
So what I was thinking was that I'll put a standard filler cap on (no breather), and drill out another hole for the breather, with a defector plate below it to stop the oil squirting straight out the breather.... but then I wondered if the breather is actually needed?
I assume it is (if you consider the engine as a sealed unit), I guess air has to get in to replace the vapout that is being sucked out?
Rocker cover breather
Started by
_jklumpp_
, Jun 04 2007 02:21 PM
15 replies to this topic
#2
_bodallafella_
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Posted 04 June 2007 - 07:44 PM
You need a breather to vent the pressure that builds up in the crankcase due to blowby. If you dont have a breather you will blow oil out the dipstick and rocker cover gaskets. Try running a catch can with a large diameter hose that goes uphill from the engine. That way a lot of the oil will drain back down the hose before it fills the can.
#3
ls2lxhatch
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Posted 04 June 2007 - 07:57 PM
Can you post a picture of your setup?
Normally you would expect a vacuum within engine so oil should not be trying to exit via the breather. Oil attempting to leave via the PCV valve is normal and can be fixed with a catch can as described by bodallafella.
Normally you would expect a vacuum within engine so oil should not be trying to exit via the breather. Oil attempting to leave via the PCV valve is normal and can be fixed with a catch can as described by bodallafella.
#4
_jklumpp_
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Posted 13 June 2007 - 01:56 PM
Over the weekend, (once we got power back!) I did the mod I talked about, and drilled another hole in the rocker cover behind the filler, and mounted the breather there. I then used a sealed filler cap, and made another defelector plate to sit below the breather. I drained the catch can again, & was suprised to see how much oil had got past the PCV outlet deflector plate.
I took the car for a run, with a few high rev blasts, and got back home and was pissed off to find oil all over my rocker cover AGAIN!
It was coming from the Breather still, and when I took the breather out and revved the engine while looking in the breather hole, I could see oil blown up on to the deflector plate, and with enough revs, spraying out the hole!
Not sure if the cause is the Hi-vol oil pump, or if I have an issue with blow-by (fresh engine with about 1200km on it)?..... Not sure what to do now?
My engine builder told me that they used to put pipe cleaners inside the pushrods to restrict the oil to the rockers (he says with roller rockers, you don't need much oil) - So I am wondering whether to try that?
I took the car for a run, with a few high rev blasts, and got back home and was pissed off to find oil all over my rocker cover AGAIN!
It was coming from the Breather still, and when I took the breather out and revved the engine while looking in the breather hole, I could see oil blown up on to the deflector plate, and with enough revs, spraying out the hole!
Not sure if the cause is the Hi-vol oil pump, or if I have an issue with blow-by (fresh engine with about 1200km on it)?..... Not sure what to do now?
My engine builder told me that they used to put pipe cleaners inside the pushrods to restrict the oil to the rockers (he says with roller rockers, you don't need much oil) - So I am wondering whether to try that?
#5
Litre8
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Posted 13 June 2007 - 02:09 PM
Are you running roller rockers? Maybe a leakdown test on the engine would identify if there is a ring seal issue.
Unless you are running a dry sump (which will usually pull a vacuum in the crankcase) then you do need some form of breather on the engine.
Unless you are running a dry sump (which will usually pull a vacuum in the crankcase) then you do need some form of breather on the engine.
#6
_jklumpp_
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Posted 14 June 2007 - 08:23 PM
Yes to roller rockers.
I keep reading about "a leak down test"... can someone clarify?
Is this just doing a compression test (I have a compression tester)? Is there something more involved?
I'd like to try & get it sorted this weekend, as I'm racing it at Wakefield the following weekend.....
So does anyone have any comment on the pipe cleaner down the pushrod trick?
I keep reading about "a leak down test"... can someone clarify?
Is this just doing a compression test (I have a compression tester)? Is there something more involved?
I'd like to try & get it sorted this weekend, as I'm racing it at Wakefield the following weekend.....
So does anyone have any comment on the pipe cleaner down the pushrod trick?
#7
FastEHHolden
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Posted 14 June 2007 - 08:44 PM
Another way is to disassemble the lifter and fill the oil inlet hole with liquid metal then drill it to a smaller size...I have heard of pipe cleaners being used in this way before.
Your best bet is to swap to a stock pressed steel rocker cover....if you have the room.
Your best bet is to swap to a stock pressed steel rocker cover....if you have the room.
#8
Litre8
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Posted 14 June 2007 - 10:33 PM
I used the pipe cleaner in the pushrod trick in my turbo 202. I never thought they were a long term solution and ultimately made up some pushrods that just had a reduced bore to limit the oil flow.
Having said that I dont think that your issue is just related to oil flow to the rockers.
A leakdown test is more accurate than a compression test for determining engine condition. Rather than measuring cylinder pressure it measures cylinder pressure loss with up to about 8-10% being acceptable for a street engine (3-5% for a race engine). And if a loss is occurring then you can often hear the source of the loss (ie. air coming out carb -> leaking intake valve, air coming out rocker breather -> rings, air coming out exhaust pipe -> leaking exhaust valve).
Having said that I dont think that your issue is just related to oil flow to the rockers.
A leakdown test is more accurate than a compression test for determining engine condition. Rather than measuring cylinder pressure it measures cylinder pressure loss with up to about 8-10% being acceptable for a street engine (3-5% for a race engine). And if a loss is occurring then you can often hear the source of the loss (ie. air coming out carb -> leaking intake valve, air coming out rocker breather -> rings, air coming out exhaust pipe -> leaking exhaust valve).
#9
_LHSL308_
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Posted 04 March 2012 - 07:02 AM
I have a similar problem to this guy. I have bought alloy rocker covers for my engine which has roller rockers. I have changed the rocker cover gaskets to rubber due to the cork ones leaking. I have put the rubber ones on and am getting leakage from the drivers side. I did not put any gasket cement on the gaskets but planned to redo them with gasket cement. Has my car put in the mechanics to get some other work done and decided to get him to redo the gaskets which I have noticed he used gasket cement only to find oil leaking from the same spot on the drivers side rocker cover gasket. I rang him and he said bring it back and i'll do it again.
My question is would a breathable type oil cap maybe help in this situation and should I have one to help relieve some of the pressure, or is it simply just a matter of having the gasket done properly?
My question is would a breathable type oil cap maybe help in this situation and should I have one to help relieve some of the pressure, or is it simply just a matter of having the gasket done properly?
#10
EunUCh
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Posted 04 March 2012 - 08:19 AM
Usually the PCV valve is connected to full vac. below the throttle plate.
The other "hole" in rocker cover usually has a pipe running to the air cleaner can with a sort
of baffle set up inside the can.
With only the small number of kays on the new engine it may just be a case of the rings
not being bedded in properly to seal blowby,takes a bit to bed rings properly.
The other "hole" in rocker cover usually has a pipe running to the air cleaner can with a sort
of baffle set up inside the can.
With only the small number of kays on the new engine it may just be a case of the rings
not being bedded in properly to seal blowby,takes a bit to bed rings properly.
#11
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Posted 04 March 2012 - 08:32 AM
This engine is well past bedded in, its done around 50,000kms and I have no holes in the rocker covers, they are the non vented type.
#12
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Posted 04 March 2012 - 08:43 AM
Shiit, i just saw the date on OPers post,my mistake.
Was replying to that one.
The crankcase needs to breathe otherwise pressure will build up inside,
Easy with single carb. because all the vac. ports are there,bit harder with multiples because they
usually dont have the ports,the catch can and then run pipe out of cat can to inside aircleaner might help.
Was replying to that one.
The crankcase needs to breathe otherwise pressure will build up inside,
Easy with single carb. because all the vac. ports are there,bit harder with multiples because they
usually dont have the ports,the catch can and then run pipe out of cat can to inside aircleaner might help.
#13
_LHSL308_
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Posted 04 March 2012 - 09:09 AM
I do have single 4 barrel carby. So how do I relieve some of the pressure inside the engine. What do you mean by the catch can, do you have a pic of what you mean?
#14
S pack
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Posted 04 March 2012 - 10:19 AM
This engine is well past bedded in, its done around 50,000kms and I have no holes in the rocker covers, they are the non vented type.
Your engine no longer complies with ADR 27 if you have no PCV valve or positive crankcase ventilation breather connected to the rocker covers.
Either have to cut holes in your rocker covers to fit these essential items or get a set of rocker covers that have the holes.
Can you post some pics of the rocker covers you have?
Edited by S pack, 04 March 2012 - 10:20 AM.
#15
EunUCh
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Posted 04 March 2012 - 10:25 AM
At base of carb there should be a large nipple for vac.(bellow throttle plate) that gets connected to PCV valve via a rubber line.
Rocker cover should have a place to fit grommet that PCV vavle pushes into.
The breather was uaually fitted via another pipe with a fitting that fitted into another grommet in rocker cover
and went to base or side(oem) of air can,, or a vented filler cap was used instead.
Sorry,dont have pics of catch can,i just run 2 lines out of rocker cover with no restriction into
air cleaner(webers),,have been "gunnado" catch can but just havnt had time.
I would make or scrounge a can that could be filled with some sort of baffle(stainless scoury pads come to mind)
then run a largish line into can somewhere towards bottom of can then have an outlet from top of can into aircleaner assy.
(just my idea and it may not work),,would probably need a drain plug at bottom of can,or get tricky and put a non return valve
in bottom of can and run a line to sump or somewhere low so that oil can drain back.
Rocker cover should have a place to fit grommet that PCV vavle pushes into.
The breather was uaually fitted via another pipe with a fitting that fitted into another grommet in rocker cover
and went to base or side(oem) of air can,, or a vented filler cap was used instead.
Sorry,dont have pics of catch can,i just run 2 lines out of rocker cover with no restriction into
air cleaner(webers),,have been "gunnado" catch can but just havnt had time.
I would make or scrounge a can that could be filled with some sort of baffle(stainless scoury pads come to mind)
then run a largish line into can somewhere towards bottom of can then have an outlet from top of can into aircleaner assy.
(just my idea and it may not work),,would probably need a drain plug at bottom of can,or get tricky and put a non return valve
in bottom of can and run a line to sump or somewhere low so that oil can drain back.
#16
_LHSL308_
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Posted 04 March 2012 - 10:25 AM
Yes I can post some pics when I get home, at work at the moment. Will a pcv valve make any difference to my oil leak problem, it doesnt leak from the other rocker cover only the drivers side one?
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