Thanks for the input.

Cam bearing not fitted correctly. Now that's a thought. Can you explain how it could be fitted wrong? I haven't replaced these bearings, but that's to to say the previous owner didn't stuff things up.

I remember one of the cam bearings has a groove and two holes (?). Is one hole smaller than the other? Are you suggesting the small hole has been lined up with the oil gallery from the crank?

So, if the bearing is fitted "upside down", all I have to do is put a restrictor on the head just before the rocker post?

Actually the Mini is an S, but original S motor is in safe keeping.

Why Dave no wristen

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"Show me the Mini!"

Dave , i`m talking about 2x 30mm pipes/hoses,,, one from each end of the rocker cover,

One on the drivers side of the rocker cover straight into a "T" piece , drain down feeding into the primary case breather hole & the pipe up to oil/breather catch tank, then another 30mm hose from the passengers side of the rocker cover, & again straight into a "T" piece down to fuel pump hole & the upper end of the "T" piece to oil catch breather tin.

not just a drain from your catch tank ...

If you built this large drain/breather system then you just simply won`t have any dramas,

if you`re getting oil spilling/spewing/comming out of the oil filler cap then obviously you`re getting heaps of oil up there & it`s not getting back down quick/easy enough
-->your rocker cover drains are not adequate

obviously you can take the rockers off & fit a restrictor into the cyl head under the pillar, or take the cyl head off & fit the restrictor in the block, but it`s just so easy to simply make big breather/drains into each end of the rocker cover -->& also doing it this way creats a very very good balanced open breathing system so as not to have any dramas even if you did have heaps of piston ring blow by at a latter date.

Most 1100-S Blocks have quite small push rod holes--> way smaller than side plate blocks,,, so when i build big engines or race engines i drill these push rod holes bigger to help with both oil drain & crank case breathing , but i still make up this style breather drain system from the rocker cover as well.

your engine is allready built, just drain really well & allow it to breath good & proper & go racing & have fun.

It`s not hard to do & then there`s no worrying about how much oil is getting up there, the more oil up there helps make sure it`s all lubed but also helps cool the whole rockers/shaft/valves etc as well.

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

Well described Matt.

I will just add a coulpe of things I have learned over the years.
Oil breathers need to be at least 1" at a minimum.
Valve springs are oil cooled.
An oil gallery with 80psi of pressure will fill the rocker cover quicker than 8 pushrod holes can drain it.
Blowby from the rings will keep the pressure in the sump from letting oil run downhill.

my mate had a standard 998 motor that had this problem, and it was the front cam bearing fitted upside down. I can't remember which way up is right (but I'd be confident it's small hole goes up), but basically it was sending the oil up into the rockers and filling it.... I've heard of others with this problem, and a quick fix was a piece of thin feeler gauge over the hole under the rocker post with a teeny tiny hole in it

I'm not going to refute what Matt (TheMiniMan) is saying about the additional drainage system, but if the front cam bearing is upside down, is there a chance some other part is being starved of oil with it going the wrong way?

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did I tell you that I won a trophy?

Thanks all contributors to this thread, especially Matt who described his breather system so well.

I might need to resort to the larger breather drains, but I wanted to at least experiment with restricting the oil flow to the top of the head.

Last night I decided I'd have a look see. I took off the roller rockers and examined the size of the oil supply hole against that of a standard rocker assembly. The roller rockers did have a slightly larger hole.

I tapped the hole, inserted a grub screw and drilled a smaller hole. The original hole was about 3.5mm; the new hole is 2mm which should restrict the oil flow by more than 50%.

I put the whole lot back together and ran the motor without the rocker cover. There was still more than adequate oil supply to all rockers even at idle. Unfortunately it was late so I couldn't check what happened at higher revs (way too loud).

The rocker cover was put back on and I'll have to wait see what happens at the next track day...which could be a while off.....moving house soon.

Thanks again....what a great forum

Dave

Sorry about the delay, was away sick, then i forgot all about looking for the info...

It was an article in the Oct-Dec 06 Mini Experience, page 55 with Neville Watts who used to work on Peter Mantons mini.

Quoted from the page in relation to what he used to do to the head to restrict the oil flow:

"From the main bearing down to the camshaft, I put a 20-thou restrictor in there, so you screw them out, and block off the oil in the cylinder head, where it feeds the rocker gear". He continued. "But, the restrictor, has got to be in the block, because if you have the oil pressure in the head, the cylinder head gasket will blow. A 20-thou restrictor will run a mini through any race meeting."

"Normally when you are squirting all this oil up the top it's getting red hot as its running back down through the head, so you don't need so much oil up the top of the head, just enough to lubricate the rocker gear."

Cheers

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I put a 80 thou restrictor in the head. This is about a 50% reduction in flow and probably 100% increase in oil pressure at the gasket.

I didn't think of the increse in pressure harming the gasket, although a 20 thou restrictor would give problems (possibly).

Next time I have the motor apart, I'll do it properly.

Again, thanks for all the help.