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Are there any limitations to using A65 heads from different years on either a 1965 engine or a 69 engine?

Gordo


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I use a new old stock "old" head (pre 1968?)on a 1971 engine. I needed to drill the rear two bolt holes in the head to a one size lager diameter.
Sometime in the history they went to one size larger diametre bolts.
The later heads (oil in frame) have a wider rocker cover than the earlier heads.


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Pre 66 heads also have smaller exhaust valves and different valve springs


VicCyclone

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1966 Victor GP
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1968 A65L

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Thanks

Any details big or small are appreciated as we look to options.

Gordo


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I sent the head from my '66 A65 to Ed at E&V for rebuild. He remarked that I have a later style head. My rocker cover has two bolts in the top I guess to bolt to the frame of a later style.

Rusty


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same here...have OIF single carb head on my 68 A65...used a couple of SS button head bolts to plug up the head steady holes in valve cover


1972 Triumph T120
1968 BSA A65
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FWIW: The holes in the OIF rocker covers are for the later head steady bolts.
Make certain those bolts are tight and sealed. They WILL leak oil if not.


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Gordo

No doubt I will miss a detail which someone else will point out, but IME, this is the A65 head selection:

62 - 65 Different valves, 5/16" rear bolts to retain the head by intake rockers. The 5/16" bolts are longer than the later 3/8" bolts and have a boss cast into the head for the longer bolts. IME, the dual carb version of this head is SWEET on the street.. grin

66 - Bigger valves and ports, 5/16" rear mounting bolts

67 - 70 - 3/8" rear bolts, same valves/springs as 66. I have run into a few odd 70's that have 5/16" rocker cover bolts and rockers covers to match eek That rocker cover will fit a 71 on head.

71 - 72 - 5/16" rocker cover studs with a slightly different pattern. Rocker cover has 2 threaded holes in top to allow head stead to bolt on.

"Balancing" a head - Mainly making sure the intake port capacities and combustion chamber capacities are matched. It allows similar intake charges and similar compression ratio and combustion side to side. I have never heard any one head was better than any other in that regards. Somewhat luck of the draw depending on tolerances. Some say the 65 and back heads actually had the best intake ports. shocked


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Rich,

You have the head differences well covered. Since my little pea brain understands pictures the best, here is an item of difference. The head on the left has a different rocker cover stud casting height than the earlier head on the right.

In this particular example, the left head is A50 Wasp ('66/'67)and the right head is A50 Cyclone ('64/'65).

[Linked Image]


1967 BSA Wasp
1967 BSA Hornet (West Coast Model)
1967 BSA Hornet (East Coast Model)
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Interesting Gary.....

Maybe today I ought to compare one of my early dual carb A65 heads to a late dual carb head.... Or work on the electrical system of the Gold Star grin ....decisions decisions laughing


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Thanks for all the info. I can see that matching rocker covers are going to be part of any swap. Now back to the parts bins.

Does anyone have the code for reading the casting numbers?

Gordo


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The outer valve cover bolt holes on the '67 - '70 are 5.6875" east/west and 5.750" north/south. Does anyone have the OIF locations?
Went out and measure the OIF cover. The studs are 5.875" east/west. North/south is the same as is the cover width.

Last edited by DMadigan; 02/27/11 12:35 am. Reason: updated measurements
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68-701 is the casting number for A65 late '67 thru '70.


1967 BSA Wasp
1967 BSA Hornet (West Coast Model)
1967 BSA Hornet (East Coast Model)
1968 BSA Firebird Scrambler
1968 BSA Spitfire Mark IV
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Gary

I compared a dual carb A65D head to a a dual carb 68/69 head. The intake ports are the same angle. Did you compare teh 2 A50 heads to any A65 heads out of curiousity?


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Can anyone ident a single carb head with 68-72 inside the casting?

Thanks

Gordo


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Based upon my BSA parts book collection plus the master price list for 1970, I reckon that it's a very early '63 0r 64 650 Star Twin Head The part# of the finished head for those years is 68-0069.


VicCyclone

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Gordo-

I have a 68-72 single carb head sitting on my bench, what did you want to know?

Rusty


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Rusty: I picked one up on ebay that is now in the mail and I was wondering which rocker cover would work on it. At this point I only have an early smooth type cover.

Vic above had it as an early head so I could be in luck.

Gordo


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Gordo,
The smooth cover will work on it. If you should decide on going to a finned cover, I have an extra one available.


1967 BSA Wasp
1967 BSA Hornet (West Coast Model)
1967 BSA Hornet (East Coast Model)
1968 BSA Firebird Scrambler
1968 BSA Spitfire Mark IV
1965 Cyclone Competition Build
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Gary: Thanks. So there are the early smooth covers, first finned covers and the later finned types with the two extra holes for a head stay.

Are there any other versions? Knowledge will help me avoid both selling and buying errors at swapmeets.

Gordo


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Gordo,

There are three types of covers:
62-65 68-0139 Smooth, 1/4" studs
66-70 68-0830 Finned, 1/4" Studs
71-72 71-2333 Finned, 5/16" Studs and head steady mount

Dry frame covers can be interchanged, but OIF (71-72) covers cannot be installed on earlier heads and vise-versa.


A smattering:
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'40 Silver Star
'37 Rudge Special
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Alex: Thanks for the info.

Gordo


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>>>I compared a dual carb A65D head to a a dual carb 68/69 head. The intake ports are the same angle. Did you compare teh 2 A50 heads to any A65 heads out of curiousity?<<<

Rich,
Don't know about the ports. I was only showing the difference in the rear cover stud casting height.


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1967 BSA Hornet (West Coast Model)
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Hey,

I am using a 71 head on an 68 engine. I am just confused about the valve cover bolts which are one of the many many bolts and nuts that I am missing. I understand the 2 studs that are on the stays are 1/4 BSF, and would require BSF nuts, which I need to get. But the 71 parts books lists 2 separate stud/bolt combos for the 5/16th UNC/UNF holes. Can one just use 5/16 UNC bolts cut to length? Seems the easiest.

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Easiest is also best in this case. Cheers PRT


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