Clutch choice for 3.8L rebuild

I’ve looked at the old postings on this topic, but still have questions about it. I’m at the point in my engine rebuild for my '62 e Coupe where I need to balance a pressure plate. My 3.8 flywheel is a drilled only for a 10" clutch, the stock being a 3-lever Borg and Beck. The diaphragm clutches have the reputation of being smoother and more reliable, although I would doubt the latter is very important for a car that won’t see high mileage these days. Diaphragm clutches are now only available in 9.5" diameter, and using one will require redrilling the flywheel. My question is:
Will I see enough real difference between the original style 3-lever 10" unit and the 9.5" diaphragm unit to justify the extra machine work? I’m inclined just to stick to the 3-lever as it’s simpler.
Let me add that I will be using a 3.8L bellhousing modified to couple with a close-ratio 4.2 4-synchro transmission and a 2.88 rear end.
Thank you for your thoughts.

There ARE 10" diaphragm clutches out there, but they are few and far between. The primary advantage of a diaphragm clutch is reduced pedal effort, especially with the pedal all the way down. So, it’s mostly a matter of “feel”. If you don’t mind heavier pedal effort, stick with the spring clutch. OTOH, it should NOT cost much to have the flywheel drilled for the 9.5" clutch. ANY machine shop should be able to do it easily with perhaps an hours labor.

Regards,
Ray L.

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Some, including me, have reported very heavy effort with “recent” 9.5" clutches. Mine is so heavy my wife can’t drive the car, despite her good physical condition (no trouble with our 928, old Vette, etc.).
Our clutch works very smoothly and the Moss shifts fine and, of course, it doesn’t slip. We did need to source a flywheel which was ‘double drilled’ and the install went fine. The pressure plate DID hit the bellhousing which I very, very fortunately found before installation (very slight grinding required.) It was a German made AP from one of the usuals.
Since others have reported this issue I’d hazard a guess they used to offer 2 flavors of clutch, regular and “heavy duty”. Reduced inventory issues MAY have caused them to now only stock the “heavy” one. It actually sucks quite a bit - in fact the semi major reason we want to sell the car, as having the car usable for my wife is a big deal for us.
Because of the, I’m sorry, stupidity, of having to take the car apart to put a clutch in, I’d never use a unit in an E-type that wasn’t ironclad guaranteed to be the same effort as an original - NOS if possible.
Part in our car is: KT9702, ordered April 2015
By the way, flywheel was 18 grams out per the speed shop balance job, which the owner said was “a lot”.

I doubt the diagram is more reliable in fact there have been a number of failures with those parts in the last several years. What it is, is lighter, hence more modern feeling. Pedal pressure is extremely light compared to the spring clutch. If you have knee issues you might prefer it. I stuck with the old faithful spring clutch.

If I recall your posts, you also sourced an original, or at least one with the same manufacturer. I wish I just stayed with the original, as trying to outsmart myself backfired.

I just got a Borg and Beck from SNG. I think it’s okay but won’t know fir certain until my hydraulic issues are sorted out.

Seems to me that with the close ratio 4.2 gearbox and a 2.88 gear 1st gear is sure going to be long!

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Thanks for the input. I do have three used 10" 3-finger pressure plates on the shelf that are probably usable, although not perfect. Maybe I should clean them up and have a closer look. I had one rebuilt quite a few years ago, and the car didn’t have excessive pedal pressure. Perhaps I’ll consider that again, considering this information. I don’t think I’ll go to the trouble for the diaphragm clutch. Although I could drill and tap the flywheel myself in my neighbor’s machine shop, it doesn’t seem worth the trouble, especially if I can use one of my old pressure plates. Does anyone know the specification for the clamping pressure? It’s not listed in the manual.

Robert, if you do the math on the close ratio gearbox (2.933 first gear), the 2.88 gives product for first gear between what a standard (2.68 first gear) box would have with 3.31 and 3.07 ratios. That translates to a speed of 7.6mph at 800rpm vs non-close ratio box of 7.2mph for a 3.31 and 7.8mph for a 3.07. I run a 3.31 rear end in my non-close-ratio 4-synchro e-type roadster, and like it very much, but would like a bit taller, and I think the combo I plan for the coupe will be ideal.