4.2 series 1 2+2 flywheel

Spark · Post by **Spark** » Sat Dec 27, 2014 9:38 pm

Flywheel doesn't look good assume this isn't correct or is it?
Can you re grind the surface of the flywheel without having to rebalance.
The grooves are about the thickness of a fingernail deep and are around the full circumference of the wheel
Any comments thanks

christopher storey · Post by **christopher storey** » Sat Dec 27, 2014 11:19 pm

Those are very strange looking groooves and look to me as though they have been machined in , rather than being the result of wear/foreign object damage . Before deciding what to do you really need to place a clutch driven plate over the flywheel to see whether the grooves actually bear on the plate or outside its periphery, in which case they are of no consequence . What is the clutch pressure plate like ?

As far as surfacing it is concerned, provided it is done properly it should not affect the balance, but in any case anyone decent machine shop who surfaces it for you should be able to get it balanced for you.

jag68 · Post by **jag68** » Sun Dec 28, 2014 1:58 am

Your flywheel needs to be re-surfaced, I can see a groove caused by the inner face of the disc as well as the more obvious outer grooves. Re-surfacing is ordinarily done on a lathe. I would expect from seeing the flywheel that the face on your clutch pressure plate would probably be equally bad and either needs to be re-surfaced or replaced/rebuilt. Somebody drove the car long after the clutch had worn beyond usable. I'd advise getting the flywheel and clutch pressure plate assembly balanced as a unit - in other words bolted together. These are all routine operations at an engine rebuilding shop and shouldn't be expensive. It's not worth taking a chance and having to remove and replace the transmission in your car if you leave it as is and it doesn't work (Can you r & r a transmission in a 2 + 2 without removing the engine?). Your machinist can tell you if it's too worn to fix - but if it hasn't been re-surfaced before it's probably fixable.

Terry Sturgeon

christopher storey · Post by **christopher storey** » Sun Dec 28, 2014 9:44 am

Another thought - before you go any further count the teeth on the starter ring. For a 4.2 there should be 133 teeth. Any other number ( probably 132 or 104 ) means it has come from another Jaguar and you will have all sorts of problems with starter mismatch, because the diameters are different

Spark · Post by **Spark** » Sun Dec 28, 2014 10:07 am

Just checked it has 133 teeth
What I don't get is the grooves are very unifom
The car has had a new clutch plate as it still got plenty of meat on it.
The grooves are reveresed onto the plate also the grooves are within the diameter of the plate.
I'm thinking just to get it machined flat, will clean it up with 400 glass paper and brake cleaner first

I assume this should be done on a lathe as terry states and not a surface grinder?

Thanks
Phil

christopher storey · Post by **christopher storey** » Sun Dec 28, 2014 11:50 am

I think my machine shop man would say that a surface grinder was best . I remember him telling me that flywheels are so work hardened that getting cutting tools to bite on a flywheel without taking chunks out of it and/or immediately blunting the tool was difficult

PeterCrespin · Post by **PeterCrespin** » Mon Dec 29, 2014 10:42 am

A surface grinder gives a finer anf flatter 'cross-hatched' (ish) finish. I turned a Jag flywheel down in my old 12" gap bed lathe easily enough but had it balanced subsequently. It's tough steel but cut perfectly well with a carbide tool.

The minor problem I had was the huge swarf which came of as a hot continuous sharp and tough ribbon because the steel was quite ductile. I'm not sure any kind of tip profile change would have broken it into chips it was such tough metal. Because of the large diameter there is a high tool speed at normal revs so I had to run the lather quite slowly.

The pressure plate is not worth rescuing, partly because it will probably cost nearly as much to mount and machine as replace, but also because I think the geometry of a diaphragm plate means a minor change in position as caused by a worn friction plate or machined pressure plate causes more of a clamping load reduction than the same dimensional change would on a 3.8 coil spring type clutch. I would assume the entire clutch is scrap and start with a new kit on a freshly-surfaced flywheel.

jag68 · Post by **jag68** » Mon Dec 29, 2014 9:16 pm

Jaguar flywheels are forged (as opposed to cast like most) so they are quite strong. You do get hot spots which are harder than the surrounding metal. I think that whether you get it ground or turned, if done by a competent shop, won't make a lot of difference. The surface friable material wears away quickly as the disc beds it. Your flywheel should have the engine serial number on the edge - so identifying it as out of your car should be easy.

christopher storey · Post by **christopher storey** » Tue Dec 30, 2014 10:05 am

Yes, it is the hotspots that make them so difficult to turn on a lathe without getting an uneven surface

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