Would a badly worn crankshaft spigot bearing cause clutch failure?

[Al Weyman]

The three race old clutch on my Camaro literally disintergrated at Silverstone stripping all the fiberous material off the centre plate and gave no warning, one moment it was OK the next slipping like hell then bang gone. I know the clutch was marginal and am going to replace with a triple plate Tilton I have but find these ultra light button clutches a bit of a pain manourvering around the paddock etc. so thought I would try a conventional unit.

Anyhow I have noticed the spigot shaft bush in the crankshaft is very badly worn, did not notice it when I rebuilt the engine but may have been like it already. Does anyone think that this could have caused such a catastropic failure as the engine is not making bundles of power.

[graham bahr]

i dont think so, the spigot is there to support the gearbox input shaft, if badly worn the spigot would allow the shaft to wander a bit, when the clutch is disengauged, and thus might cause the shaft and clutch plate therefore to be revolving slightly exentrically, and hold eveything slightly off centre when re_engauged this would put added load on the centre of the plate, wear teh splined section and possibly break the bit that houses the springs but i doubt it would effect the linning

[Tim Falce]

If you hadn't noticed the bearing wear before was it because you didn't look or didn't notice? Maybe the crank bush wear is due to a clutch breaking up. Is the gearbox spigot shaft bearing and the clutch cover OK?

I have had no end of engine trouble which turns out was caused by my clutch pressure plate being out of centre. I had it balanced on the engine but it seems the arms mounting the pressure plate to the cover bend and cause the pressure plate to go out of line and out of balance, setting up vibration through the engine.
I have virtually destroyed three engines by using the same clutch cover on all of them (the only common denominator on all three) and had to change to a multi plate setup.

I suppose if the bush in the crank is worn enough then movement could occur in the spigot shaft causing the plate to fail. The slipping before hand could have been the start of it breaking up.
Was it a standard clutch and are you sure you weren't heavy handed on your down-shifts? This apparently caused my problem.

[Al Weyman]

It was a standard beefed up clutch single plate and I am used to racing with a multiplate set up but I don't think I was particularly abusive. I did not notice any wear before but this is qite a lot and thought I would have notices, I will check for any tell tale swarth later.

Interesting what you say about misalignment Falcemob as I am wondering if the actual box is misaligned on the bellhousing as one of the lugs is damaged and looks like it has been for some while (I left the box on the bell housing before so would not have noticed but as only 4 big bolts like an old Viva I dropped it out first this time and made it easier to get off). I did also have to excert a fair bit of pressure to prise the box off the bell housing which I put down to the clutch being mulched but the centre plate was in fair condition apart from zero lining material both sides. I have a spare Muncie gearbox case and wonder if it is worth swapping everthing over.

Hey just had a thought, last time I used this car what 13 or 14 years ago, I broke two 400cu crankshafts on the trot and put it down at the time to running an externally balanced 400 cast crank but the Americans use the crank and it gives no problems in fact the mains ar 1/8" bigger than the 350. Thats why I gave up on the 400ci engines I wonder if some misalignment would cause this as well. When I originally bought the car as a road car the manual box was a conversion, got me thinking now.

[Tim Falce]

My team mate replaced his standard cover with a heavy duty one which did one or two races before breaking.
I was also told that spinning the car can do serious damage to the clutch (more likely to be my problem) as the speed differential between wheels and engine can be too great and something has to give.
I now have a 7.25 inch triple plate with sintered centre plates and don't have much trouble in the paddock apart from a bit of juddering if I can't let the clutch up completely.

It could be worth checking out the g/box alignment if you seem to be having similar problems, you may have been lucky with the clutch going so quickly.

[greenamex2]

How much movement was there in the spigot bearing? If it's anything like a Corolla one then it would be a millimetre or two at the most which wouldn't affect the clutch.

I know when big V8's are used with the Renault UN1 transaxle in mid engined kit cars there is often a misalignment problem. In this case it is ALWAYS the gearbox that breaks first, not the clutch.

[Al Weyman]

I would say at least two mm of play.

[graham bahr]

Originally Posted by Al Weyman

I would say at least two mm of play.

cant see that was your problem then, and even if it was im sure it would be the centre of the clutch rather than the lining that would fail

[R59]

too much torque for that Vauxhall Viva clutch plate you put in there al!

[Al Weyman]

You may be right Rob, thing is I took this engine out of the IROC race car complete with clutch and put a new centre plate in it and I do believe the car had been used in competition but maybe not although the rest of the engine was quite well put together and had some reasonable bits in it so am surprised who ever owned it skimped on the clutch. I knew it would not last for ever but was surpised by this total failure in such a short time. Mybe they just stuck it in to sell it.

[midgetman]

Just a thought Al. Although our MG Midgets don't put out anything like the grunt yours does, we have trouble because modern clutches sold as "competition" just aren't man enough for the "big bore" engines. They used to, but not any more since they went asbestos-free. Perhaps the driven plate spec has changed in the 12 years since you last raced like ours has?

It certainly sounds like accelerated wear, can't see that mis-alignment or vibes would do that.

[Al Weyman]

Actually Midgetman you may well be right, no asbestos these days, never thought of that. The last time I raced it I used the triple plate sintered Tilton button clutch, proper job and I have just bought new plated for it and will stick that back in it is just that they are extremelly light and the mass is located at the centre using just an automatic trans driveplate to carry the ring gear. Improves accelaration and you get nice crisp gear changes and it sounds like a proper engine when you blip the throttle as the pick up is instantanoeus but it is a sod to manouvere around the paddock as I said before.

[R59]

Al, just a thought, how about a single paddle plate?

[Al Weyman]

I have a twin plate McCleod Paddle clutch in my other car and that has an alloy flywheel and is almost as bad around the paddock.

The problem as well is the Muncie has a very long first gear and the final axle ratio is also a bit tall but as I don't really want to rev this engine much over 6000rpm so I am a bit stuck with it as it will only give me say 145mph at say Thruxton which is not really enough as it is and I can't be arsed to keep changing ratios for different circuits as it is a pain with the GM 10 bolt axle which I must use. The Tilton unit is great actually and would have still been servicable after three seasons racing it is just as I have it out I have replaced the clutch pack for good measure. I am just surprised with the level of tune with this engine that it required this type of clutch maybe it is making better power than I thought!

[graham bahr]

Originally Posted by Al Weyman

I I am just surprised with the level of tune with this engine that it required this type of clutch maybe it is making better power than I thought!

torque my man torque, thats what eats clutches and transmissions, as power is basically only torque at revs, so your low? powered engine doesn't make big torque at high revs, but i bet it still makes big torque and thats what does the damage

[graham bahr]

Originally Posted by midgetman

They used to, but not any more since they went asbestos-free. Perhaps the driven plate spec has changed in the 12 years since you last raced like ours has?

.

you might have a good point there, a friend of mine who used to prepare lots of race and rally engines in the 60's and 70's always struggled to understand why modern racers are using such high tech clutches, when back then even quite extreme engines got by on fairly std clutches.

although it has to be said, for normal road use modern clutches last 2-3 times longer than their old asbestos relatives

[Al Weyman]

Maybe in normal road use they are OK but as soon as subject to any excessive heat they cannot handle it. I noticed the first time I did a racy start at Pembrey it felt a bit marginal, something I am not used to as with the sintered clutches you just drop them and bang you're away, no burning clutch smell! In the second race I was a bit careful and it actually cost me a couple of positions by Hatchetts so maybe it is all just as well in the long run.

[Al Weyman]

Been replacing the clutch today with the Tilton unit but I think I found out why the clutch went.

I had previously messed with the linkage and I reckon it had a faulty clutch release bearing with a little notch in it where it slides over a sleeve on the box. Well I recon it with the incresed throw it was catching on the sleeve and held the clutch open hence the problem. I actually wish I had sussed it before I put this racing Tilton triple plate sintered clutch in because apart from the expense they are a dog to drive, either in or out no messing, and very hard to drive around the paddock or manouvering in and out the workshop. Still I should see a performance increase with the lightweight unit.

Actually I reckon the jambed open clutch probably minced the spigot bearing and not the other way around.

[Madman280]

As a matter of course I like to replace the gear box input seal if the spigot bearing is worn. All of that movement can't do it any good and oil on the clutch will kill it just as fast as slipping it.

[Al Weyman]

Good point Madman only the old Muncie don't have one as such as I recollect just an oil thrower arrangement and there was no evidence of leaking.

Incidently I have stick the Tilton triple plate 7.5" in with just a automatic ring gear driveplate (no flywheel as such) and fired it up today and it feels real good and ticks over nice. If it will work OK on a big V8 anyone contemplating this in a 4 or a 6 banger then go for it!

[dtype38]

A big V8 has quite a lot of rotating mass already before you fit a flywheel Al. If you tried that on a little high compression 4 it might just stop

[Tim Falce]

Originally Posted by Al Weyman

Incidently I have stick the Tilton triple plate 7.5" in with just a automatic ring gear driveplate (no flywheel as such) and fired it up today and it feels real good and ticks over nice.

What have you used for the clutch to mount on and run against?

[Al Weyman]

The Tilton is a complete unit in itself Dtype and so in effect has a little 8" flywheel. The whole unit bolts directly to the crankshaft and the Auto flex plate is sandwiched between the crank and the Tilton.

[greenamex2]

I have practically a flex plate for a fly wheel on my high comp 1600 4. I also have a light crank, rods, pistons, single plate Helix race clutch and NO front crankshaft damper.

The engine also has 320 degree PLUS cams and 10.5mm lift (a lot for 1600).

It ticks over fine, albeit at 1600 RPM. I can drive it round the paddock OK despite a very high first gear (for a 1600) and can light up the tyres on the start to problem.

I really believe that the ultralight flywheel causing problems is just a myth or perhaps an excuse from engine mappers who can't map engines properly. If you are on carbs then it's probably because you haven't got a high enough intake velocity low down for the carb to meter correctly.

[Al Weyman]

No crankshaft damper? Don't think you could do that on a Chevy.