Engine breathing problems
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Engine breathing problems
Hello all.
I was wondering if someone could help with my problem.
On the road it is fine but on the track when used flat out Oil is being ejected from the engine through the breathing system.
Both rocker covers have a 1/2 inch outlet which vent to a catch tank which has a single 1/2 inch outlet that vents to another container. This sytem has been fine previously.
Rover V8 4.6 Mechanical 238 cam, yella terra roller rockers. Rev limiter set to 5800.
This seems to be related to the Yella terra roller rockers somehow as before they were fitted it was fine. The rockers have oil holes in the top and was wondering if that could be the cause by spraying and misting the oil by the action of the rockers. ( logshot )
Makes no difference with or without baffles in rockercovers.
Anyone had a similar problem? and how can I rectify?
Thanks in advance
Mark
I was wondering if someone could help with my problem.
On the road it is fine but on the track when used flat out Oil is being ejected from the engine through the breathing system.
Both rocker covers have a 1/2 inch outlet which vent to a catch tank which has a single 1/2 inch outlet that vents to another container. This sytem has been fine previously.
Rover V8 4.6 Mechanical 238 cam, yella terra roller rockers. Rev limiter set to 5800.
This seems to be related to the Yella terra roller rockers somehow as before they were fitted it was fine. The rockers have oil holes in the top and was wondering if that could be the cause by spraying and misting the oil by the action of the rockers. ( logshot )
Makes no difference with or without baffles in rockercovers.
Anyone had a similar problem? and how can I rectify?
Thanks in advance
Mark
Hello Mark,
Does your engine have a windage tray fitted?
You may have already found the cause as you indicated the problem only began after installation of the roller rockers. Was this the only change that you made at that time?
What grade of oil are you running? I assume that this grade has remained unchanged?
Ron.
Does your engine have a windage tray fitted?
You may have already found the cause as you indicated the problem only began after installation of the roller rockers. Was this the only change that you made at that time?
What grade of oil are you running? I assume that this grade has remained unchanged?
Ron.
4.6 Rover 3500 P6B
It sounds like it's always being breathing that volume of air, it's just now that air happens to have lots of oil in it (probably because of the rockers). As you note, the std. rockers only dribble oil out.
Not sure what the answer is though.
Chris.
Not sure what the answer is though.
Chris.
--
Series IIA 4.6 V8
R/R P38 4.6 V8
R/R L405 4.4 SDV8
Series IIA 4.6 V8
R/R P38 4.6 V8
R/R L405 4.4 SDV8
Actually thinking about it I think I fitted this catch tank at about the same time
http://www.rallydesign.co.uk/popup_image.php?pID=13088
Perhaps I should start by getting a larger diameter outlet fitted.
The internal size of the outlet is 9mm maybe thats a bit small?
Could this be causing the problem?
Thanks
Mark
http://www.rallydesign.co.uk/popup_image.php?pID=13088
Perhaps I should start by getting a larger diameter outlet fitted.
The internal size of the outlet is 9mm maybe thats a bit small?
Could this be causing the problem?
Thanks
Mark
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- Top Dog
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- Location: Sidcup, Kent, UK
Mark,
I think you are right that it's rocker related, Rover V8's are renowned for pumping oil up to the rocker cover area if sustained high rpm is being used.
I think the fix is to reduce the flow by putting restrictors in the two oil feeds in the heads at the front of the engine which also give a bonus of more pressure at the mains and big ends.
I thing you would find a refernce to this in Hamills book and probably Hardcastles as well.
It's probably down the the roller rockers allowing a greater flow of oil because of their design.
The only other thing you can do is reduce crankcase pressure by having a return hose from the catch tank, to vacuum via a PCV valve.
Kevin.
I think you are right that it's rocker related, Rover V8's are renowned for pumping oil up to the rocker cover area if sustained high rpm is being used.
I think the fix is to reduce the flow by putting restrictors in the two oil feeds in the heads at the front of the engine which also give a bonus of more pressure at the mains and big ends.
I thing you would find a refernce to this in Hamills book and probably Hardcastles as well.
It's probably down the the roller rockers allowing a greater flow of oil because of their design.
The only other thing you can do is reduce crankcase pressure by having a return hose from the catch tank, to vacuum via a PCV valve.
Kevin.
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- Top Dog
- Posts: 2334
- Joined: Sat Aug 18, 2007 5:09 pm
- Location: Sidcup, Kent, UK
Mark,
Not sure what you mean re the catch tank mods.
To reduce crankcase pressure you need to maintain venting as per the original system but with the catch tank in the loop.
The catch tank needs to have one inlet from one rocker cover and one exit at high level so the tank acts as a seperator.
The other rocker cover needs a decent size air filter on it to allow air to be drawn through the engine and you need a PCV valve in the exit pipe from the catch tank which goes to the large vacuum port on the Edelbrock carb.
Somebody recently posted a variation with two vacuum pipes, one from each cover via a Y connector but you would still need to have an inlet to allow air to be drawn in so the system is balanced.
Whatever you do you have got to reduce the volume of oil that is accumalating in the rocker area, I'll have a look at my books and see if I can find the section that deals with this problem and what the recommendations are. alternatively you could give V8 Developments, John Eales or Real Steel to see what they recommend.
Kevin.
Not sure what you mean re the catch tank mods.
To reduce crankcase pressure you need to maintain venting as per the original system but with the catch tank in the loop.
The catch tank needs to have one inlet from one rocker cover and one exit at high level so the tank acts as a seperator.
The other rocker cover needs a decent size air filter on it to allow air to be drawn through the engine and you need a PCV valve in the exit pipe from the catch tank which goes to the large vacuum port on the Edelbrock carb.
Somebody recently posted a variation with two vacuum pipes, one from each cover via a Y connector but you would still need to have an inlet to allow air to be drawn in so the system is balanced.
Whatever you do you have got to reduce the volume of oil that is accumalating in the rocker area, I'll have a look at my books and see if I can find the section that deals with this problem and what the recommendations are. alternatively you could give V8 Developments, John Eales or Real Steel to see what they recommend.
Kevin.
Kevin
I have a pipe going from each rocker cover to 2 inlet connections on the side of catch tank (see pic above) then an outlet at the top which at the moment leads to an open topped clear container (so I can see what is coming out).
Im thinking that the 9mm outlet is too small.
Also I dont want to feed hot air into the inlet hence my open system.
My previous system was the same except for a filter on catch tank with outet about 15mm
Thanks
Mark
I have a pipe going from each rocker cover to 2 inlet connections on the side of catch tank (see pic above) then an outlet at the top which at the moment leads to an open topped clear container (so I can see what is coming out).
Im thinking that the 9mm outlet is too small.
Also I dont want to feed hot air into the inlet hence my open system.
My previous system was the same except for a filter on catch tank with outet about 15mm
Thanks
Mark
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- Top Dog
- Posts: 2334
- Joined: Sat Aug 18, 2007 5:09 pm
- Location: Sidcup, Kent, UK
Mark,
Understood. I 've looked at Hardcastles first book and on page 124 it covers the problem of ecessive oiling if using roller rockers, I think doing the mods suggested will be the only way of solving your promlem as whatever you do with the catch tank it will still pump the oil out.
Basically it involves tapping threads in the oilways, installing a couple of carb jets into the feed holes in the heads or the block then drilling them out to approx to .094"
Obviously a bit of a fiddly job on an assembled engine but can't see a way round it.
Kevin.
Understood. I 've looked at Hardcastles first book and on page 124 it covers the problem of ecessive oiling if using roller rockers, I think doing the mods suggested will be the only way of solving your promlem as whatever you do with the catch tank it will still pump the oil out.
Basically it involves tapping threads in the oilways, installing a couple of carb jets into the feed holes in the heads or the block then drilling them out to approx to .094"
Obviously a bit of a fiddly job on an assembled engine but can't see a way round it.
Kevin.
Thanks Kevin,
Do you think this would work as a temporary measure until I take the heads off.
Fit thin shims under rocker pedestals with small oil hole 0.94"
Obviously i would need to adjust the valve clearances to suit.
The oil holes are the right size for an M6 tap but I dont really want to tap the holes insitue. Thought I could eventually get some M6 grub screws and drill them out to 0.94"
Thanks again
Mark
Do you think this would work as a temporary measure until I take the heads off.
Fit thin shims under rocker pedestals with small oil hole 0.94"
Obviously i would need to adjust the valve clearances to suit.
The oil holes are the right size for an M6 tap but I dont really want to tap the holes insitue. Thought I could eventually get some M6 grub screws and drill them out to 0.94"
Thanks again
Mark