Bell Housing Locating Bolt

Old Fogey UKOld Fogey UK Posts: 763Expert Adviser
Please could someone tell me the precise dimensions of the critical locating bolt  that goes at the bottom right of the bell housing on prewar 254s ?
I think it's a 3/8 inch UNF but I don't know the overall length or the length and diameter of the unthreaded shank.
The engine restorer used a fully threaded bolt (which I understand is a no-no) and that has probably contributed to my clutch problem.
Thanks !


  • 54coupe54coupe Posts: 780Member
    edited October 5
    I think that locator is a sleeve. If it's like every one I took apart, there will be a counterbore in the back of the block, and in the bell housing. The O.D. on the newer engines is .619", and the I.D. is somewhere between .4375 and .500 The I.D. size is not critical, as long as the bolt passes through it. Add the depth of both counterbores to the thickness of the rear engine plate for the length of the sleeve.
  • GeoffGeoff Posts: 4,293Senior Contributor
    MUST be a 7/16" diameter bolt, inserted from  the front so that the shank is a tight fit in the holes of the engine plate and the bell housing.  Was originally a stepped bolt, with a 3/8" u.n.f thread on  the rear end, but a straight 7/16' bolt is fine.  There is a dowel in  the top left  hole.  if you use a smaller bolt the housing will move, mis-aligning the clutch spigot.  
  • Old Fogey UKOld Fogey UK Posts: 763Expert Adviser
    Geoff - when you say the bolt has to be inserted from the front, do you mean from the engine plate into the bell housing  or the other way round ?
  • GeoffGeoff Posts: 4,293Senior Contributor
    From the front, with the nut at the back, and the head of the bolt at the front (that is towards the radiator).   The shank of the bolt locates the bell housing in the correct position.  You may need to jiggle things around a little when installing the bolt. 
  • Old Fogey UKOld Fogey UK Posts: 763Expert Adviser
    Thanks, Geoff.
    I've recruited a working party of three (1 automotive engineer, 1 car mechanic plus me as dogsbody) to put everything together again.
    I'm just waiting for the re-lined clutch disc to arrive and then it's all systems go.
  • GeoffGeoff Posts: 4,293Senior Contributor
    One thing I should have emphasised, it must be a full shanked bolt with just the end threaded.
  • Old Fogey UKOld Fogey UK Posts: 763Expert Adviser
    I have found one like that, Geoff, but thanks for the reminder.
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