What thread are Alloy head rocker box bolts

[old53]

I Have lost  the short bolt from in side the rocker box, actually it had the wrong one fitted to an old head and I would like the right bolt for my new head. I am having some difficulty in finding a supplier locally. Is it  BSF or BSC thread can you help Thanks

[RichardL]

Carey (I think it is),

When bolt size questions come up I often go to burtonbikebits.net as a reference. They are quite good for including size information with part numbers. Here, I believe the part number you are seeking is 15-1355. What they say about this part is:

15-1355        BOLT - 5/16" CEI X 1 1/2" UH

...and the link is:

http://www.burtonbikebits.net/TRIStock.pdf

Richard L.

[trevinoz]

I have that bolt as 1-11/16" long. I had better check.
Trev.

[trickytree]

Acording to my 49-53 parts catalogue 15-1355 is....

5/16 CEI x 1.5" (.625" thread length, .218" head thickness and .525" hex!!!)

[old53]

Thanks Guys for the lead
CEI  is what I was looking for
Google revealed
-- CEI (Cycle Engineers Institute)
This thread series was superseded by BSC (British Standard Cycle) thread.
These are different names commonly used for the same threads. 60 degree thread angle, rather than the 55 degree of BSW and BSF.