Hi Julian

At the risk of boring everyone else rigid I still don't know which cylinder head I've got. The casting no does not appear to be recognised by any of the "dealers". So what alterations were made and when. All I know is that at some stage the Valves were changed. That infers that the seats were also changed.

Do you reckon that I can check this out simply by measuring the seat diameter or what else might you suggest.

What were the valve changes and was the head casting actually changed in any way.

Your help and advice appreciated.

Mike

The service bulletins below might help.

Could you post photos?

I  :)am about to try to post some pics. Anything is likely

Try agen

This is the third attempt. If I still have it wrong ?

And finally

The previous owner THINKS 1967.  AS can be seen?? it is stamped 68-72  and AM. All the holes are 3/8th

Mike

First photo frpm 1962-65 workshop manual showing valve sizes.

Second photo from 1966-68 workshop manual showing valve sizes, which stayed the same until the end.

Hi Julian Thanks again.

Unfortunately I still don't have enough info to be certain. I am leaning toward the later head. So some more advice please how would you suggest that I go about finally nailing this one down.

My thoughts are to get one of each vales and offer them up and see whether one sits way down in the seat or sits very proud.

I'm in no great hurry so I have plenty of time to get it right.

?

Mike

Hi,
    I had similar problems, to narrow identification:

1962 - 1969 Valve guides are this shape   https://www.feked.com/bsa-a50-a65-bronze-inlet-and-exhaust-guide-68-0809.html
1970 -1972 Guides are this shape   https://www.britishbikebits.com/valve-guide-g542pb-bsa-a65-1971-72#.WdkVQ2hSyUk

1962 - 1968 The two rear head bolts are 5/16" diameter
1969 - 1972 The two rear head bolts are 3/8" diameter

1962 - 1970 The rocker cover studs are 1/4" diameter
1971 -1972 The rocker cover studs are 5/16" diameter (the rocker cover has the head-steady bracket, hence the larger studs)

I also used the valve specification as Julian previously posted.

From your posted images you have a 1969.

Hope this helps....