I attended a vintage race the other weekend and had the chance to talk to some of the Mini runners about many different subjects. The conversation started out talking about what was causing his Mini to get a little weird coming out of the fast turns. Of course there can be a whole lot of reasons for this, but this did lead our conversation towards "limited slip diffs".

When we first started talking about LSD's he told me he was using a Quaife type. When I said I now only use the clutch type (ie. Salisbury, TranX type) his comment to me was that they didn't give you a chance to rest and I bit my tongue. What I wanted to say to him was "do you want to go fast or rest"?

Now I know everybody has different opinions, but perhaps they make decisions on the LSD to use by advertisements, rather than by experience. So that's what I am going to give you, my experience. I've tried four different types available for the Mini. I'm not going to get into how they work, just the reasons I like or don't like each unit, as racer to racer.

1. SALISBURY CLUTCH TYPE

Yes, indeed this one will give your biceps a work out. They can have their preload adjusted by altering the clutch packs or by machining the case. I ran mine with 100 to 110 LBS of preload, normal is 50 to 75 LBS. With this LSD, it has a natural self straightening effect. Thus you can run considerably less front suspension castor which in turn makes steering effort much more pleasant, even at 110 LBS of preload.

2. JACK KNIGHT "PAWL TYPE"

This one is hardly worth considering, it is twitchy and darty and I have my doubts they were ever designed for front wheel drive. I've driven them in rear wheel drive with no bad comments, but not FWD. Besides, they freewheel if you break a CV or an axle.

3. QUAIFE 'TORQUE SENSING" TYPE I

have used this one a few times as has Fortech and we both took them out! I've been told to give it another chance and I may, but I don't plan on it in the near future. This one allows you to rest, but my experience with them is that they are less than confidence building. They seem very inconsistent from turn to turn, they give a feeling of not holding the car into the corner. I've also been told by some greater powers that this LSD works good when new but when worn - watch out! I was advised to replace the diff every season or so, to not have this problem. This doesn't sound very good to me. I was also advised that I would have to adjust my chassis around the LSD, maybe so but not right now! This type of diff is also a freewheeler.

4. 'TRAN-X" CLUTCH TYPE

This one really is a modern day Salisbury (with improvements). It is pre-Ioad adjustable and seems to be very well made (after some initial manufacturing start-up problems). The final jury is still out on this one but it does seem to be better than the original Salisbury in that it can hold the car straight using much less preload, like half as much (wastes less horse-power). And it does have the ability to lock and unlock where the Salisbury did not. This feature makes corner entry and exit much nicer and it is still easier on the biceps (and you still use less castor). But...if you are used to the old Salisbury this diff is different.

Depending on how you can specify the diff when ordering, it can be a little sensitive to getting on and off the throttle. It can be a little darty if you are too abrupt with the throttle, so it reminds you that smoother is faster.

On the technical side, this month I will tell you about what I discovered about my valve train problems that showed up to haunt me at the SCCA Runoffs. Well, to start with, there was not enough oil getting to the valve train. This was caused by an engineering oversight in the design of the roller rocker assembly. Either the oil-feed hole in the pedestal was too small and restricted oil flow up to and through the rocker assembly, or more probably, the rockers had no oil squirters to direct oil at the valve and pushrod tip, thus reducing the oil quantity there. Or it could have been a combination of both. Second, on this particular block, the oil quantity number 1 push rod hole had not been drilled correctly by the factory. The last 1/8" at the bottom of the hole was reduced by about .050". This, at high RPM, was causing the push rod to rub and to bow at this pOint, which in turn caused the upper push rod cup to wear, allowing the ball and socket to disintegrate. Thirdly, not all push rods are equal. Some have a narrow ball radius and some have a mushroomed ball radius on the down side end. When the valve lash is set, the mushroomed radius locates the pushrod into the Iifter cup pretty snugly, where the narrow radius allows the pushrod to dance around quite a bit. This allows all the push rods to rub somewhat in the push rod holes at high RPM despite that they had not during measuring and assembly.so the conclusions I have come to are that for the time being I will use Crane push rods for they have a mushroomed radius ball, and I will return to Mini Spares roller rockers made by Titan Motorsport that have never given me a bit of problem since t 984, and I do not care if the motor smokes a little on over-run because I have a little too much oil in the valve train.

Race report: The first race of t 994 has come and gone. It was a double National at Phoenix International Raceway. joe Huffaker jr. drove the Fortech Mini. The weekend started out pretty rotten. I hadn't been feeling too well healthwise, and of course when I buckled into the car things didn't get any better. Actually it worked out quite well, me not feeling well and joe's inexperience in the car was a perfect match. For both races I felt my worse. I got a really bad start, they all flew by me and I ended up with two of them between me and joe. On the third lap, in an effort to get by those two, I made a move that put my CV jOints in jeopardy. One of them broke, so I became onewheel drive. I finished the race that way, all 25 laps. Let that be a testimony for the Tran-X diff. I could not have run that many laps on any other diff ... period. In Sunday's race I got a good start but the cars from behind were the same story. I got back around them on the first lap, sensibly this time! Then when I went to downshift for the first time, the trans locked in fourth, and when it did unlock, it jammed in second. It seems I had my first 50 cent failure. The bush that the external shift rod runs through had come un-fitted.