Bolts: Clutch to Flywheel: 4.2

[norman m. macleod]

Hi all,
Can anyone advise the correct bolts for the above duty (Six off)with respect to:-
(1) Steel grade, i.e., high tensile or not, and
(2) Dimensions, overall length under head,and what length plain and what length threaded......

I've been sent what are essentially 5/16" x 1" set-screws (threaded all the way......) from one of the usual suppliers, and I feel instinctively there should be a small unthreaded section under the head, say 1/4" or so, for this particular (critical) duty.....? Any comments/wisdom most appreciated.......and possibly where can I get the "correct" ones......?
Best regards to all,
Norman.

[Mark Gordon]

Norman,
Right you are. I have my engine disassembled for a rebuild and the bolts which hold the clutch to the flywheel do have about a 1/4" unthreaded section beneath the head. Others could tell you if that makes any difference or not.

[Heuer]

Maybe this will help:
Nuts, Bolts and Fasteners specs: http://dl.dropbox.com/u/8496016/Fastener%20codes.htm

[christopher storey]

Norman : this subject came up on Jaglovers just recently , and I discovered that there are variations. For instance, my S1 4.2 Factory parts manual suggests that these fasteners are UFS.137/8R which using the code which David has provided suggests they are 3/8 UNF setscrews which are 1/2 inch long. Yet other people say that their flywheel is drilled for 5/16, which is of course the size you have been sent. All very peculiar, but at least it confirms that setscrews , and not bolts, seem to have been factory fitment . I do wonder whether the 137 is a misprint for 131 which would denote 5/16

[1954Etype]

I can confirm that mine are 5/16.

[norman m. macleod]

Thanks all,
Christopher you are correct re the manual, and for that reason I ordered UFS.137/8R's as per my own Jaguar manual, and 3/8" diam. items arrived. The flywheel is drilled and tapped 5/16", of course, and, on remonstrating with the supplier, they were of the opinion that the manual was incorrect, as you postulated, and the listing should be 131 (5/16"). I am unconvinced, however, that a setscrew is appropriate in such an arduous duty, and the narrow highly loaded land should be plain, about 1/4". The supplier has just responded in, agreement, so the second lot, even at 5/16", were also incorrect. Mark confirms this too, with his current disassembly, thanks Mark........Third lot on the way ex supplier......
Thanks again All,
Best regards,
Norman.

[steve3.8]

Norman,

the set screws that hold the clutch to the flywheel don't have any shear load to take , the dowels eliminate it . Grade 5 is probably what the suppliers have sent you ? , grade 8 at a guess originally .