Pre Spa check up

[erictharg]

I pulled the engine and gearbox from the racer to check them over before Spa in September. The engine is running fine. Pulls well and uses little oil. But it is leaking oil from one or more places. The gearbox has now done more than two seasons of racing and also working fine but it seemed sensible to check it over (especially as the shriek of the straight cut gears mean you would never hear the sound of any impending failure).
One source of engine oil is clearly the timing cover, as the front of it has been deformed by someone (ahem!) using it to gently lever the pulley off with two screwdrivers instead of digging out the correct hub puller. This means the seal is not sitting square to the axis of the pulley and so not working very well. I'll use the puller in future - as ever shortcuts usually come back to bite you! I'm also replacing the clutch plate. I'm still running a stock Midget 1275 clutch and its worked fine so far. The cover is balanced with the crank and flywheel so I'll keep it but fit a new centre plate. Should be good for a couple years more.
The gearbox looks fine. No obvious wear to anything. The gear teeth and dog rings look as new. The ball bearings are of course looser than when new, but still smooth. The layshaft is just beginning to mark up where the needle rollers run on it, and is the weakest link in the gearbox. So I'll replace the layshaft and bearings, and also the needle roller that sits in the back of the input shaft.
When I bled the brakes at Rocky the rear fluid was discoloured suggesting the seals are wearing in the slave cylinders, so I have ordered two new rear cylinders (5/8" bore instead of the stock 3/4" - means I can run the bias bar closer to the middle instead of adjusted right over to the front cylinder). £11 each from Mini spares. Don't you just love those prices?
I'm worried that the Romac crank damper I bought used on E Bay when building the car has had a good soaking of oil from the leaking timing cover seal. I don't know if that might be affecting the elastomer insert that hold the two parts of the damper together. I've got a second hand Metro damper that looks in good fettle but I don't know how accurately it is balanced. The only other alternative is one of MED's new dampers, but they're £140, and Mini Spares do the stock Cooper S damper but they need balancing before fitting. I read that the danger speed for resonance in an A Series crank is high 6000 rpm range, where mine spend a lot of time. Think I'll call MED and plead poverty. See if they can do me a better price...

[adamwilkinson]

Hadn't realised you are running a SCCR 'box, don't you just love the sound of them!

May I suggest checking the bung in your rocker shaft...

Might also be worth renewing the diff oil seeing as you are replacing other fluids. I should probably check/replace the oil in our 'box and diff.

[Westfield 129]

I've been running a Romac damper for several years, and from time to time, it gets oiled from worn front seals. I don't think that there is a problem with this, as the unit is balanced.

If you find that you have a problem with setting the timing, then the damper has slipped internally (the timing mark has moved), but this would be a rare occurrence with a high quality damper such as the Romac (though I have three stock dampers that this have slipped). I doubt that there is any problem with the damper. It is not going to change its balance just because it was oiled.

The clutch, though it is balanced with the rotating assembly, can be changed. It would be silly to think that when you had to do a clutch change that you had to disassemble the engine and re balance it. I change clutch covers often, and don't think much about it. The engines run the same, and produce the same power after they have been renewed. I personally have never had any luck with just a change of clutch disc, and always change the entire assembly. If you are worried about the balance, you can have the cover rebuilt. I often do that, as my local rebuilder makes a better cover than the OEM.

Damper pullers are cheap. Any three slot puller will work, with some long bolts (the damper has three threaded holes already). You don't need anything special. The price for a bolt on puller is about the same as for a pair of big screwdrivers, and a lot less than a front cover.

[adamwilkinson]

Speaking from experience, if your clutch cover has been balanced with the crank, rods, pulleys, flywheel etc then replacing the cover without rebalancing the whole lot will end up costing you more in the long run. When you see how much material is taken of the cover, to then think you can just slap another one on is daft - UNLESS, of course, you had a 2nd one balanced at the time the first was.

We had a clutch cover break during a race leaving me without a clutch. We stupidly just bolted on a spare unbalanced cover and ended up bending the crank by the end of the season!
Lesson learnt, and steel crank bought.

Bolting on an unbalanced cover might work for road use, but I'd strongly recommend not doing so for racing where you are constantly at the upper end of the rev range.

[erictharg]

Thanks for the feedback on the damper Jan. I'll stick with the Romac for now given your good experience with them.

Re. clutch, there's nothing wrong with the existing one, but it seems sensible to put a fresh plate in. Gives me more life and restores the clamp load compared to a thinner worn disc. There's no reason not to use the pressure plate again, given its face is not marked at all.
I would opt for having a new cover balanced before fitting though. I'm not sure the factory balancing is good enough for a race engine. I suspect that once I get a limited slip diff the clutch will have to work harder and that may be the time to upgrade to the 7.5" version.

All the oils will be changed - diff, engine and of course gearbox.

[Westfield 129]

My experience with clutch covers is that they loose clamping force about the same time that the disc is worn. The loss of clamping force is more evident than disc wear. I have had slipping clutches with good discs, as the spring clamping force was lost.

Clutch covers are balanced, and marked, as is the flywheel. Installing a new clutch cover should duplicate the balance of the original, unless you are using a completely different design.

"In the long run" is interesting, as my race engines seem to last about forever, or more than 40K miles... Which is several lifetimes for a race engine. In any case, I have yet had to re size a BMC A crank due to bearing wear, even after installing several clutches on a balanced reciprocating assembly.

But on the practical side, it is simply not practical to disassemble the engine just because you need to change the clutch cover, as well as being unnecessary. The idea of balancing with the clutch cover is to correct for the balance of the production clutch cover, and installing a new clutch cover using the marks provided by both the cover manufacturer, and the marks provided by the engine balancer on the flywheel ensures that the replacement clutch/flywheel assembly will be balanced within reasonable tolerances.

All the production clutch covers are the same balance (and marked to indicate how they are to be installed. Installing one on your balanced reciprocating assembly, properly clocked to the markings, wont change a thing.

[adamwilkinson]

I think we are going to have to agree to disagree on this subject, especially as Charles is only planning on changing the plate itself.