The BSA Workshop > Twins

A65 Camshaft

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Mike Farmer:
 :) :) :) :)
Good morning. I am rebuilding an A65 engine to Thunderbolt spec. I have a camshaft No 68-0473 which I am lead to believe is high lift???. Out of a Spitfire or something of that ilk.(According to Draganfly,-----I don't know) If I remember rightly the correct one is 67-356??

I know the dear old Thunderbolt with standard pistons etc doesn't need that amount of breath, so what will be the probable effect if I use it
I suspect very little but I would be interested in your thoughts.

Mike 8) 8) 8)

68 473 is the standard cam for the A65 Thunderbolt, Lightning Spitfire etc.

The A50 Royal Star and some pre 1966 A65 were fitted with cam 68 103.

Cam 67 356 will not fit an A50 or A65.

Mike Farmer:
Thanks for that. Now I know where I'm going. Some of these books are simply unbelievable wit duff info.

Go a step further--are the different valve collars interchangeable??Not that I know what year my cylinder head is.

Only if you use the matching collets. See service bulletin below.

You say some of these books have duff info. Do you use the parts books available in the members area? They have the ones for all years of the A65 and they are the genuine BSA ones.
I find one of the benefits of using these is you can compare the camshaft for instance on say a 1965 against a 1966model and glean when changes if any were made.
Caveat here, some of the post 1971 OIF parts lists can be a bit iffy as they changed parts mid season as the development continued until the abrupt stop in 1973!!


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