Engine breathing problems

mgbloke · Post by **mgbloke** » Tue Mar 24, 2009 8:02 am

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

RoverP6B · Post by **RoverP6B** » Tue Mar 24, 2009 10:25 am

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.

mgbloke · Post by **mgbloke** » Tue Mar 24, 2009 10:35 am

Ron
Yes windage tray fitted.
Problem started a year ago when i fitted camshaft and roller rockers.
Cant think what else it could be.
Wonder if I can block up the holes in the rockers? I presume they are there to oil the roller tips.

Have always used 15w40 with good results.

Cheers
Mark

ChrisJC · Post by **ChrisJC** » Tue Mar 24, 2009 10:47 am

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.

RoverP6B · Post by **RoverP6B** » Tue Mar 24, 2009 11:20 am

Hello Mark,

I feel its probably best not to block the holes in the rockers.

What volume of oil is being ejected over what distance?

I assume that oil is not being pushed from any other points?

Ron.

mgbloke · Post by **mgbloke** » Tue Mar 24, 2009 12:11 pm

Well one 15min session round Silverstone GP yesterday lost about 1/3pint of oil into the catch tank.
The valley gasket gets damp with oil but not really a leak.

I have contacted Yella Terra, hope they reply.

Thanks
Mark

ChrisJC · Post by **ChrisJC** » Tue Mar 24, 2009 12:15 pm

Can the oil in the catch tank be drained back into the engine?

Chris.

RoverP6B · Post by **RoverP6B** » Tue Mar 24, 2009 12:39 pm

That does seem like rather a lot of oil...

Oil mist on the valley gasket almost sounds like too much internal pressure.

Ron.

mgbloke · Post by **mgbloke** » Tue Mar 24, 2009 1:38 pm

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

CastleMGBV8 · Post by **CastleMGBV8** » Tue Mar 24, 2009 6:07 pm

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.

mgbloke · Post by **mgbloke** » Sat Mar 28, 2009 9:20 am

Think I will eliminate the catch tank first by making the outlet bigger to say 15mm id or should it be bigger?
Kevin
I must get a copy of Hamills & crdcastles books. Neet to get to the bottom of this problem, its been bugging me for ages.

Mark

CastleMGBV8 · Post by **CastleMGBV8** » Sat Mar 28, 2009 12:11 pm

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.

mgbloke · Post by **mgbloke** » Sat Mar 28, 2009 4:31 pm

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

CastleMGBV8 · Post by **CastleMGBV8** » Sat Mar 28, 2009 5:11 pm

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.

mgbloke · Post by **mgbloke** » Sun Mar 29, 2009 2:39 pm

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