[Healeys] BN2 Trans Dowel Bolts

[Michael MacLean]

As I said in a post post to the list, I was looking for the dowel bolts to assemble (on center) the BN2 transmission to the engine backplate.  Curt Arndt was kind enough to furnish pictures of the correct dowel bolts used in production of the 4 speed side shift BN2 transmission.  The only supplier of these original style bolts in the UK did not have any in stock, but did list them on their web site.  They may be available in the future I would venture to guess.  My only alternative was to ask the wisdom of the list.  David Nock was very helpful with this problem. He told me the later dowel bolts for BN4 type cars would work.  As luck would have it, he sells them at a better price than you can find online.  I took the plunge and purchased the two dowel bolts required for centering the transmission on installation and they arrived in the mail today along with nylon insert nuts and lock washers.  The lock washers play an important part in this.  When you measure the two thicknesses of the backplate and the transmission flange in the location of the two dowel bolts, you come up 1/16th of an inch (plus a little for the recess in the trans flange face) greater in length than the unthreaded shank of the dowel bolt.  The big lockwasher is thick enough to allow you to tighten the nyloc nut all the way down.  The lock washer is thicker than 1/16th of an inch.  I understand the temptation to just use some 3/8ths bolts in all the holes, but when I tried the dowel bolt in any of the other holes not intended for dowel bolts, it was a very loose fit.  So add to the fact that all 3/8ths bolts used might make it hard to center the transmission to avoid undue lateral pressure on the components inside the bell housing and the transmission output shaft bearings.  This information only relates to BN2 transmission installation as I have no experience with the BN1.  As an aside, I don't understand the round head with two flats of the original dowel bolt.  The BN2 transmission has a recess in the flange where the dowel bolt head is located,, but the hex head of the BN4 dowel bolt fits fine in this recess as if the recess is only the to mark the spot where the dowel bolt goes.  OK, class dismissed.Mike MacLean

Sent from AT&T Yahoo Mail on Android
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://autox.team.net/pipermail/healeys/attachments/20210327/083ffe76/attachment.htm>