The blokes on this forum have been a terrific help winnabey, and there is no way I could have restored Minnie without their advice. I've worked on lots of different cars over the years but never a Mini and there are so many things particular to the Minis that need people who know what they're doing to help sort out a problem.

The forum is a credit to the admin team who do all the hard work behind the scenes to keep it running and weed out any potential issues to ensure the forum remains a group of friendly blokes helping each other enjoy their Minis.

Cheers Rocky

".... I also restricted the air cleaner intake a tad, using a piece of pvc tube which is about 1.6mm thick, with the intent being that more suction may be (or maybe not ) on the hose from the rocker cover....."

This is somewhat counterintuitive... Pretty much all tuning mods involve opening up the air intake capacity of the engine... which then allows the addition of more fuel to produce more power. I've never seen anyone advocating reducing the air intake.

Even if your restricted flow into the carb was balanced by the air being "sucked" into the filter case via the breather crankcase, you're substituting clean colder air with hot dirty oily air... Can't be good.

Cheers, Ian

G'day Ian,

I agree with what you're said and all I was trying to achieve was to make sure that there was sufficient suction on the hose from the rocker cover after the mods I made. I thought that maybe by slightly restricting the main intake of the air cleaner, it may lead to a bit more suction on the rocker cover hose.

Thinking about it now after reading your comments, I'll take the bit of PVC out (it's just slipped into the end of the air cleaner).

I hadn't considered the unintended consequences of restricting the air flow. I've been focused on trying to address the oil discharge from the chest cover and narrowed my thinking just down to that issue.

Thanks for your info.

Cheers Rocky

The concept of increasing the depression in the air cleaner is probably a good one as far as crankcase breathing is concerned, and it would appear the factory gave this some thought.

The picture below shows the pipe connection at the air cleaner for an 850. There is an opening to atmosphere outside the air cleaner interior space, and a restrictor in the pipe where the hose attaches. No doubt the size of the restriction and the opening shown work together to give the required amount of depression in the hose to the rocker cover, probably like the venturi action of an old fashioned insect spray pump.

I get the feeling if you want to run the late model carburettor you have, you need the corresponding side cover, rocker cover and oil cap but your custom arrangement evidently does the job.

Thanks eightfifty - good pics of what the original set up was.

When I got Minnie, she had a pair of mismatched 1 1/4 SU's on a custom inlet / exhaust manifold that as far as I know, was made sometime in 1964. It also had a bonnet scoop on it but that was welded up way before I got it.

At the time, I was told to get rid of the twin setup and that a single 1 1/2" carb would give much the same amount of fuel as the twins and would be less hassle - so that's what I did. When I picked up the carby, I had no idea it was from a later model. Interestingly, the bloke who reco'd it for me never mentioned it was from a later model, although he knew it was going onto an early 850 and supposedly set it up to suit it.

In hindsight (which is a wonderful thing), I think I would have possibly been better off just putting it back to standard, although I must say I'm happy with the way it runs and drives with the only issue being the oil breathing out of the chest cover. The other thing I would have done - now I know about it - was to change the chest cover for a later one with the outlet going up and then bending down which would have most likely eliminated the oil breathing issue. I have one that I could put on however I'm a bit hesitant to change them due to the access. The one on the engine has a cork gasket and if it came off in one piece it would be ok, however if some of it stuck to the block, I could see bits of cork ending up in the engine somewhere which wouldn't be good. As you know, it's real hard to access and see down the back with the manifolds on and at this stage, I'm not inclined to pull them off if I can find a workaround that solves the oil problem.

As you point out, when you make a change with one thing (the carb in this case), there's a potential knock on effect to consider.

Next time I see a stock standard 850 I'll check out the chest cover and air cleaner to see how is was originally done.

It's been cold and wet here the last few days so I haven't had a chance to clean everything up yet and take it for a longer drive for a couple of hours to see how the new setup works. When I do, I'll post the results.

Cheers Rocky