29 replies to this topic

[slpj24]

Thanks for that number Dan. I guess the cam bolts can take more, but not the cam plate without it distorting, and I've been doing more than 8lb to those bolts I would guess.

1st let me explain more clearly what I mean about the engine plate.
The engine plate does not distort. The cam plate does. The engine plate recesses due to the eroding effect of oil flowing between the front face of the engine plate, and the thrust face (camshaft side) of the cam plate.

If the cam plate is bolted too tightly, it compresses at the bolt holes. The white metal surface spreads out a little. If the cam plate is then re-used again, as I have done, when the already compressed cam plate is bolted down, it has the effect of raising the stretches of cam plate between the bolt hole locations. Arching the cam plate. Thus a gap is created between the front face of the engine plate, and thrust face of the cam plate, and oil flows through these gaps. The hot oil under pressure over many engine miles, has the effect of eroding the front face of the engine plate. But the rear face of the engine plate stays flat.

However.
I've now noticed, that the threads in the face of the block, that secure cam plate, have been pulled slightly proud of the block face. This I think might have resulted in the engine plate not sitting completely flat against the block, and I have had oil leaking through the gasket at the rear of the engine plate at this point. In my case to the inside, and not the outside as I think you are describing.

Regarding the oil feed to the camshaft. On the Spridget block and I would imagine the Mini block is the same in this respect, there is an oil feed from the front crank main, directly to the front camshaft bearing. The bearing itself, has a slotted hole that extends towards the front. This slotted hole lines up with the crank main oil feed. Oil enters the camshaft bearing at the rear of the slotted hole, and each sweep of the camshaft the front groove in the camshaft, must "collect" a slug of oil from the front of the oil slot in the bearing, which it carries round to the cam plate hole. At least that's how it looks.

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Edited by slpj24, 29 February 2012 - 12:20 AM.

[Ethel]

Having any sort of gap around the cam retainer plate is going to rob the thrust faces of their oil feed and I expect the chain get a fair bit of its from what is centrifuged out onto the chain pulley. Maybe there's not only more oil (I doubt there's that much extra as it'd still need to navigate the cam journal.), but it's also getting sprayed around in a way that allows more to run past the entry to the oil separator. As I think someone suggest above, if it gets saturated in oil then air won't get through and the induction would have to "drink" the oil, like an Essex girl with a Pina Colada.

[jaydee]

Have not read the full thread, but oil filling up the breather on the timing cover, sounds to me the crank seal is worn and not able to hold the higher pressure you have when engine is warming up.

[liirge]

One thing I've noticed is that you've got as 1275 with only one breather connected, this isn't the most advantageous of systems. You should have the one above transfer case connected as well.

[Dan]

Have not read the full thread, but oil filling up the breather on the timing cover, sounds to me the crank seal is worn and not able to hold the higher pressure you have when engine is warming up.

Not sure quite what you mean by this but the last thing a worn out crank seal would do is hold oil in the timing chest, it would be leaking rather than building up.

Liirge the engine's not in a Mini, it's an inline A and doesn't have a transfer case or other breathers.

[slpj24]

Hi Ethel, Think of it like this. The crankshaft doesn't need a front retaining plate, because of it's arrangement of caps and thrust washers. If the camshaft were installed in the same way, with no end retaining plate, then oil would seep from the front end of the camshaft, in the same way it must do in small amounts, from the crank front main. ( I think Liirge must be referring to this oil feed in his post?)

Anyway, now factor in, that the front journal of the camshaft, has a forward facing open ended groove. As you know this groove feeds oil out via the small hole in the cam retaining plate, once in 360 degrees. Now imagine the retaining plate wasn't there. There would nothing to regulate the amount of oil flowing out, other than the pressure, and the size of that groove. So at the one extreme, no retaining plate at all, and the other, the retaining plate controlling the oil. Anything in between, allows increased oil delivery to the timing cover, with the maximum being the no retaining plate situation.

The greater the gaps under the camshaft retaining plate, the more the oil flow can approach the maximum amount possible, under the no retaining plate scenario. And hence fill the timing cover sufficiently to cause this problem.

Whilst I want to find a distinct cause to this issue, I also want a solution and a backup in case the excess oil flow still happens.

So I have indeed been looking at the Mini breather setup. I want the PCV. I think it's good and don't want to vent to the air.

On the 1275 Spridget setup, the only breather hose, is from the timing cover canister, to the y piece, and then to the carbs inlet. I'm thinking of adding another. My modification is to add ANOTHER connection point. The regular one connects to the timing cover, just as now. The hose come up towards the Y piece, but is connected through a T piece first, which then connects to the Y piece. Meanwhile, ANOTHER hose is run from an additional breather canister, connected to the drilled fuel blank. The hose from this connects the remaining pipe on the T, and thus they are BOTH connected to the Y, and to the carbs.

Suction applies to both. If +ve sump pressure develops, it is countered by both pipes. But now, the draw is from both sides of the front of the engine block. Directly from the sump, and via the small opening in the front of the block face, that leads to the timing cover chamber, and in both cases, down from the rocker cover, via the meshed oil filler cap.

If oil then fills the timing cover, and a vacuum develops in the timing cover hose --, now, because of the additional connection at the fuel blank, that will cause more air to enter the oil filler cap, down into the sump, and out via the drilling in the fuel blank. So the vacuum will try to release by sucking on the breather connected to the drilled fuel blank, rather than the timing cover hose. But all the time, the breather is still drawing away from the potential of +ve sump pressure.

ALSO, the pull through the 2nd canister at the drilled fuel blank, will be to pull against the oil column in the timing cover hose, but from the other side of it, via the small block opening that leads to the timing cover chamber. In that sense, it will turn that small hole in the face of the block, into a manifold assisted overflow, for the excess oil in the timing cover. When the oil level reduces, below the level of the internal entrance to the timing cover canister, the vacuum in the timing cover breather hose will die, and oil will cease to be sucked up.

That’s the theory anyway.

So whilst I still want to know why, I also want a way to combat it, if it does happen and can’t be prevented.

[Ethel]

I just meant the clearance in the cam journal must be comparable to what should be around retainer plate. Once you've restricted the area a second similar restriction won't make a lot of difference.

The fuel pump breather sounds like a plan, maybe give it a baffle to deflect oil thrown straight off the cam? You could also rig up a manometer to see what's happening to the pressure between the two.

[Dan]

The breather layout you propose will be much the same as many twin carb Mini installations. There is an aftermarket breather available to fit to the fuel pump boss if you aren't using a mechanical pump.

[slpj24]

Where do I get a manometer cheap though? I don't know anyone with one, and for a one off, 50 quid seems a bit steep. But it would be a useful tool to have though.

Dan , Ethel, That was my next question. Where do I get an oil seperator canister? I've seen the adapter block on mini spares I think, but I can't find anyone selling a canister to bolt to it. I could knock one up, I suppose, but it would be nice to get a decently made one, rather than my own crude version.

[Ethel]

Scrapyard most likely, some cars use the oil filler cap, I've seen a display rack of them in Halfords - PCV pick 'n mix?

[Dan]

The adaptor you have probably seen is the one from Mini Mania, and if so it includes a nicely engineered baffle. The baffle is very important, as Ethel says a hell of a lot of oil comes off the cam at higher speeds. It doesn't have the large chamber attached though as you say, just a threaded outlet. I have seen one of the Mini specialists offering a conventional breather that fits directly to the boss I'm sure but I can't remember who makes it right now. It is quite short, about half the length of a normal one, to clear the manifolding of a Mini. Not sure how much space there is in a Spridget application. Specialist Components make a very complex breather box that fixes to the boss for their twin cam kits, it has many connections and could make quite a modern system that also drains oil back from a catch tank if you hooked it up right. It's expensive though. I'll have a dig about in catalogues and things and see if I can remember where the simpler one is from.

[Shifty]

If it a specialist part for the Sprite then have a look here

http://www.petermaye...k/catalogue.htm

[slpj24]

Thanks for those suggestions. I looked on Peter mays site, but couldn't find one. I'm also trying to avoid specialist parts, cost wise. :) If I can find one from a Mini i figure that's the cheapest route.

I did find one listed in the USA, but it was unavailable. Forget which site it was, maybe little british cars or something like that, But then there would be shipping too. So I'd like to find one closer to home. Maybe an old tappet chest breather that I could modify or something.

Ah, just found one for the clutch housing on minisport, but the flange is at the wrong angle. I wonder if that would be easy to swing that around to mount on the fuel blank? Is that something that's been done?

P.S. There's reasonably good space, because the 3 branch leaves the fuel blank fairly clear.

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•  mini clutch housing breather.jpg   56.52K   1 downloads

Edited by slpj24, 01 March 2012 - 10:20 PM.

[slpj24]

It seems everybody sells breather filters, but not the oil seperator can. They all want to do away with PCV, and I want to keep it.

[Ethel]

That looks like the late pattern clutch housing breather, that fits under the servo on the last revision of Mini brakes.

A Metro Turbo oil drain & hose would get you started, but a bit of d-i-y fabrication would be cheaper.