9 or 10 inch clutch

[tr2tr6]

Hi guys,
Can anyone help ime please, Iam rebuilding my '63 fhc with the original engine and moss gearbox, what is the best clutch assembly to use, the original 10 inch or the new 9 inch diaphram unit? Any help would be appreciated. Thanks!

[christopher storey]

The diaphragm unit is unquestionably nicer to use because it is much lighter in terms of pedal effort . Provided your flywheel is drilled for both 10" and 9.5" units, it is a bolt straight on feature . With a 4.2 its torque capacity is a little suspect ( mine smells if repeated steep hill starts have to be undertaken ) but with a 3.8 you should have no problem. I have heard that you can in fact get 10" diaphragm units, but I have not seen one myself, so an enquiry with Barratt's may be worthwhile

[Moeregaard]

I would go with the 9.5" clutch. I did this with my very early 4.2 FHC and was happy with it. The 10" diaphragm unit fitted to the early 4.2-litre cars had a checkered reputation and many owners actually reverted to the arm-type 10" clutch used by the 3.8-litre cars. I spoke with the owner of a well known Jaguar restorer/supplier over here, and he strongly recommended fitment of the 9.5" clutch. I did and it was much nicer to use, with less pedal effort and smoother take up.

[mark10337]

I did read somewhere (probably on this forum) that the later 9.5" clutch was a cost saving from Jaguar on the later cars. When I took mine on my Series 2 apart, I found it was a 10" fitted - most likely a PO at some stage. I kept it as a 10" and have been quite happy with it so far.

[tinworm]

Well - as mentioned by an earlier respondent you can only fit a 9.5" clutch if the flywheel is drilled for it -and this would be late 3.8 only so '64 if you have the original flywheel. if I remember correctly the bolts for the 4.2 are 5/16" and the 3.8 is 3/8" so you would need a set of bolts too. I find the spring clutch has a smoother and progressive feel to it whereas the 4.2 clutch has the 'in or out' style as befits a diaphagm as it goes over centre - slightly lighter action though, as mentioned before. I would not feel a 9.5" is necessarily an improvement over a 10" where the original flywheel is used - you would have a bit of a gain with it fitted to the much lighter 3.8 (dual drilled) flywheel as the 10" clutch cover is much heavier .
So just to clarify 3.8 flywheel - light
4.2 flywheel- heavy
10" clutch - heavy
9.5" clutch - light
So your best combination would be 3.8 flywheel and and 4.2 clutch for a sporting driver - if you have the necessary parts.
Dont forget the bellhousing /starter difficulties with swapping bits around - there have been one or two threads on here about this.

best of luck Barrie

[64etype]

I had my early '64 flywheel drilled for the 9.5" bolt pattern. (and the locating dowels).

[andrewh]

Ditto, my 62 3.8 had the flywheel redrilled. the 9.5 inch is a nice clutch.

[shauniedawn]

What is the actual difference in flywheel weights between the two?

Shaun

[tr2tr6]

Many thanks guys for all the useful information. After considering all of your advice, I think I will stick with the 10 inch clutch as I don't fancy going along the lines of re-drilling my flywheel. Thanks again!

[Jeff Poston]

I recently went to put a new 9.5 inch diaphragm clutch into my 1969 S2 OTS. I discovered it had a 10 inch diaphragm clutch. I thought all S2s had the 9.5 inch. Anyway the flywheel was drilled for the 9.5 inch as someone else has pointed out the bolt sizes are different, but also the dowels are a different size (1/4ins instead of 5/16) and are in a different location. My machine shop pulled the old dowels and put new smaller ones in and also tapped clean the holes for the new bolts.