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Too much oil in rocker cover
https://ausmini.com/forums/viewtopic.php?f=5&t=32514		 Page 1 of 2
Author:  Dave Elliott [ Tue Jun 05, 2007 1:16 pm ]
Post subject:  Too much oil in rocker cover
Thought I'd change the subject of this thread to better describe the problem I'm having.

Hi All,

Sorry, I've been off-line for a while....not enough time to work on my Minis.

I've got a question about roller-rockers.

I've inherited a fairly hot Cooper S with a 1380 motor. Every time it is brought to the track it blows a heap of oil out the breathers and into the catch tank.

Thinking it was a blow-by / ring problem, it had a rebuild, but the problem has remained.

Talking to people at the track it appears that if a motor has roller rockers it is necessary to restrict the amount of oil that can get to the rockers, otherwise the rocker cover can fill very quickly and oil can be forced out the breathers before it has a chance to fall back into the gearbox.

I have heard of people using a restrictor in the oil gallery to the rockers.

Anyone know what size this restrictor should be?


Cheers,

Dave
Author:  9YaTaH [ Tue Jun 05, 2007 2:38 pm ]
Post subject:  Rockers
Firstly Dave...I don't think your problem has anything to do with roller rockers....sure sounds like the average Mini pressurising the sump problem to me :idea:

Ian (1071) reckons:

Not really relevant IMHO. The standard rockers do not impact/control the flow of oil to the top of the engine. This oil flow is controlled by a groove in the front bearing face of the cam shaft and a corresponding exit hole in the front cam bearing.

If you insert the cam bearing back to front you get an uninterrupted oil flow to the rockers and a problem something like that described...

My Titan roller rockers performed perfectly for many years without any such issue ..but subsequently failed when exposed to 9000+ rpm :(

Cheers, Ian
Author:  Dave Elliott [ Tue Jun 05, 2007 2:56 pm ]
Post subject: 
Thanks for the reply Ian.

Sure, I agree, the crankcase is pressurising, especially at the revs this motor pulls, however under normal conditions this should only cause a minimum of oil to be thrown into the catch-can.

I know it depends where the breathers are and what type they are. In my case the motor has 4 breathers and without fail it’s only the rocker cover breather pipe that shows signs of passing a lot of oil.

I'm sure that there is too much oil flow to, and sufficient drainage from the rocker cover area. Once the rocker cover is full crankcase pressure increases because I have effectively lost one breather and the situation then gets worse.

Roller rockers do not need as much lubrication as plain bearing or bushes and I think that by cutting down the oil flow to the rocker assembly that you stop the rocket cover filling too fast.

Reducing the oil flow to the rockers might not solve the problem I have, but it may stop one of the symptoms.


Cheers,

Dave
Author:  smac [ Tue Jun 05, 2007 4:52 pm ]
Post subject: 
I'm lost - rollers may or may not need less lubrication, but that's irrelevant. Why would rollers make the top cover fill more/faster than it would with standard rockers?
Author:  Dave Elliott [ Tue Jun 05, 2007 5:16 pm ]
Post subject: 
Sorry for the confusion.

A 1380 motor (73.5mm bore) running at revs between 4000 and 7000 rpm is going to send a lot of oil to the top of the motor. I dare say the same engine with normal rockers would also fill up the rocker cover under the same conditions.

I have been told that roller rockers require less lubrication. This means that I could restrict the amount of oil getting up to the top of the motor. If I can do that, the oil may be able to drain back into the gearbox faster than it is supplied to the rockers.

If I can achieve this, filling up my catch-can should be a thing of the past.

Does anyone know the hole size of a restrictor to reduce the oil flow to the rockers?


Cheers,

Dave
Author:  britishvita [ Tue Jun 05, 2007 5:54 pm ]
Post subject: 
I remember seeing something in the Mini Experience (maybe 2 or 3 issues ago) a few months ago where they restricted the oil flow up top, it was an interview with someone that tuned mini engines in the 60's.

Will try and remember to have a look for you
Author:  KLAS [ Tue Jun 05, 2007 7:13 pm ]
Post subject: 
to my knowlege: yes, roller bearing rockers needs less oil than normal bushed rockers. the needle bearings have more spaces where the oil will be pushed out (between the needles and outer race/cage).
you may wach it by watching inside the filler neck and revving the engine, the oil may spray out of the rockers.
Author:  drmini in aust [ Tue Jun 05, 2007 7:45 pm ]
Post subject: 
The usual method of restricting it is tap the oil feed hole at top of block then screw a grubscrew in, with a small hole drilled in it to restrict flow. I'd say for full rollers, a 1.5mm hole would be a good start. :wink:
Author:  mr moke [ Tue Jun 05, 2007 8:32 pm ]
Post subject:  hi dave
i'm having the same problem as you my motor is also a 1380 but i;ve got sandard rockers and my motor has only done 900klms since it's rebuild :(
Author:  PetenSoaf [ Tue Jun 05, 2007 8:40 pm ]
Post subject:  Re: hi dave
mr moke wrote:
i'm having the same problem as you my motor is also a 1380 but i;ve got sandard rockers and my motor has only done 900klms since it's rebuild :(


Nah, your's is your own fault for getting all those backyard yobbos to work on your car. . . :D
Author:  mr moke [ Tue Jun 05, 2007 9:42 pm ]
Post subject:  hi pete
come on no;1 yobbo don't be like this if you were a good yobbo you would fix it for me :lol:
Author:  Dave Elliott [ Wed Jun 06, 2007 9:53 am ]
Post subject: 
britishvita wrote:
I remember seeing something in the Mini Experience (maybe 2 or 3 issues ago) a few months ago where they restricted the oil flow up top, it was an interview with someone that tuned mini engines in the 60's.

Will try and remember to have a look for you


Must not have read my copy cover to cover as I usually do :)

We're moving house shortly and my wife has already started packing....no idea where she's hidden my Mini mags.

It would be great if you could find the article.


Thanks,

Dave
Author:  TheMiniMan [ Wed Jun 06, 2007 11:26 am ]
Post subject: 
There is another way to combat the problem without taking the cyl head off etc, & that is to simply make 2 decent sized drain pipes , externally from each end of the rocker cover back to the both the primary case breather & the fuel pump hole in the block. both these places are perfect for both crank case breathing pipes & oil drain return pipes

i fit this system on all our race engines & large road/rally engines regardless of whether the cyl head gets too much oil or not.
Author:  Dave Elliott [ Wed Jun 06, 2007 1:10 pm ]
Post subject: 
TheMiniMan wrote:
There is another way to combat the problem without taking the cyl head off etc, & that is to simply make 2 decent sized drain pipes , externally from each end of the rocker cover back to the both the primary case breather & the fuel pump hole in the block. both these places are perfect for both crank case breathing pipes & oil drain return pipes

I fit this system on all our race engines & large road/rally engines regardless of whether the cyl head gets too much oil or not.


Yep, this is what I have set up too, on a slightly smaller scale; any oil getting to the catch can is drained back into the sump via the fuel pump hole.

However what I find is happening (probably due to excessive blow-by at high revs) is that the rocker cover fills up and oil starts weeping from around the oil filler cap (non vented type). I don't think this is an ideal situation and would prefer to reduce the amount of oil getting up there in the first place.

Is there "blow-by" normally generated from the valve guides? This may be the cause of the over presure I'm experiencing in the rocker cover. If the supply of oil is too great for the normal head-to-sump drainage path then this path is effectively blocked and any additional blow-by pressure in the rocker cover will result in oil being forced out the easiest path (the breather pipe).

Dave
Author:  simon k [ Wed Jun 06, 2007 4:40 pm ]
Post subject: 
I reckon the cam bearing is in upside down - I can't see how roller rockers would CAUSE more oil to be in the rocker cover - they may not NEED as much oil, but wouldn't CAUSE more to go up there

Dave Elliott wrote:
Yep, this is what I have set up too, on a slightly smaller scale; any oil getting to the catch can is drained back into the sump via the fuel pump hole.


PS: it's not an S motor if it has a fuel pump hole... but I'll get back in my box now
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