BSA Owners' Club Forum

The BSA Workshop => Twins => Topic started by: Mike Farmer on 30 September, 2017, 11:08:41

Title: A65 Camshaft
Post by: Mike Farmer on 30 September, 2017, 11:08:41
 :) :) :) :)
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)
Title: Re: A65 Camshaft
Post by: JulianS on 30 September, 2017, 11:41:52
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.
Title: Re: A65 Camshaft
Post by: Mike Farmer on 30 September, 2017, 13:32:56
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.

Title: Re: A65 Camshaft
Post by: JulianS on 30 September, 2017, 14:24:32
Only if you use the matching collets. See service bulletin below.
Title: Re: A65 Camshaft
Post by: Editor on 30 September, 2017, 16:11:59
Mike,
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!!
Title: Re: A65 Camshaft
Post by: Mike Farmer on 30 September, 2017, 17:17:30
Hiya Mr Editor, :)

In truth, no, not as a matter of course. I have a selection of books that have arrived unbidden in my drawer. However now that you have been so kind as to prompt me, in future I shall do so. Seriously thank you.

Julian Hi.
Thanks for your input, now I understand more fully. Further question,-- As I have no idea what year my cylinder head is from, are the lower valve collars interchangeable. And are there any others that might fit. I know that I can buy new ones but I wish to avoid that wherever possibly for such simple parts.

Mike 8) 8) 8)
Title: Re: A65 Camshaft
Post by: Mike Farmer on 01 October, 2017, 16:02:58
Hi. 8)

My cylinder head is stamped 68-72. I have been through all my bits and trawled the BSAOC archive but cant find that No. So what have I got.

Must admit that I would like to get this as right as possible, so that I can buy the correct valves etc. Are the valves A65 interchangeable. Must confess that previously I would have just bought A65 Valves because I wasn't aware they differed.

So despite the haggard looks I am still young enough to learn????????????

Mike :) :)
Title: Re: A65 Camshaft
Post by: JulianS on 01 October, 2017, 17:03:41
There will be a casting number on the head somewhere around the rocker spindle mounts.

Post some photos they might help us identify the head.

The inlets changed for 1966 but you can trace the different numbers through the parts books same with the spring seats.
Title: Re: A65 Camshaft
Post by: Mike Farmer on 01 October, 2017, 17:51:47
Hi.
That's where the casting mark  68-72 is situated???