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A65 Head interchangeability? #360032
02/25/11 5:11 pm
02/25/11 5:11 pm
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Comox BC Canada
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Gordo in Comox Offline OP
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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


Without frequent roadside repairs there is no fun in riding!
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Re: A65 Head interchangeability? [Re: Gordo in Comox] #360037
02/25/11 5:21 pm
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Ger B Offline
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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.


Ger B

Re: A65 Head interchangeability? [Re: Gordo in Comox] #360042
02/25/11 6:02 pm
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Pre 66 heads also have smaller exhaust valves and different valve springs


VicCyclone

1965 A50 Cyclone Clubman
1966 Victor GP
1967 Victor Special
1968 Victor Special
1968 A65L

2009 HD FXDC
Re: A65 Head interchangeability? [Re: Gordo in Comox] #360046
02/25/11 6:11 pm
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Thanks

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

Gordo


Without frequent roadside repairs there is no fun in riding!
Re: A65 Head interchangeability? [Re: Gordo in Comox] #360087
02/25/11 10:48 pm
02/25/11 10:48 pm
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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


1967 A65 Lightning
1967 Triumph T20 Mountain Cub
1967 Moto Guzzi V7
1969 B44 Victor Special
1966? Royal Enfield Interceptor
Re: A65 Head interchangeability? [Re: ] #360119
02/26/11 1:19 am
02/26/11 1:19 am
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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
1968 MGB Roadster
1979 Chevrolet Camaro Berlinetta
1969 Honda Mini Trail
1939 farmall f30 tractor
2004 Honda Shadow Aero
1972 BSA Thunderbolt
1975 yamaha xs650b
1972 Norton commando project
Re: A65 Head interchangeability? [Re: Gordo in Comox] #360171
02/26/11 8:30 am
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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.


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
Re: A65 Head interchangeability? [Re: Gordo in Comox] #360199
02/26/11 2:42 pm
02/26/11 2:42 pm
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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


Life is too short to drink cheap, bad beer.
Re: A65 Head interchangeability? [Re: Gordo in Comox] #360210
02/26/11 3:52 pm
02/26/11 3:52 pm
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Gary E Offline
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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).



1967 BSA Wasp
1967 BSA Hornet (West Coast Model)
1967 BSA Hornet (East Coast Model)
1968 BSA Firebird Scrambler
1968 BSA Spitfire Mark IV
Re: A65 Head interchangeability? [Re: Gary E] #360213
02/26/11 4:19 pm
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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


Life is too short to drink cheap, bad beer.
Re: A65 Head interchangeability? [Re: Gordo in Comox] #360217
02/26/11 4:47 pm
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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


Without frequent roadside repairs there is no fun in riding!
Re: A65 Head interchangeability? [Re: Gordo in Comox] #360225
02/26/11 6:06 pm
02/26/11 6:06 pm
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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
Re: A65 Head interchangeability? [Re: Gordo in Comox] #360253
02/26/11 9:38 pm
02/26/11 9:38 pm
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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
Re: A65 Head interchangeability? [Re: Gary E] #360367
02/27/11 4:21 pm
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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?


Life is too short to drink cheap, bad beer.
Re: A65 Head interchangeability? [Re: Gordo in Comox] #360419
02/27/11 9:59 pm
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Can anyone ident a single carb head with 68-72 inside the casting?

Thanks

Gordo


Without frequent roadside repairs there is no fun in riding!
Re: A65 Head interchangeability? [Re: Gordo in Comox] #360447
02/28/11 12:43 am
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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

1965 A50 Cyclone Clubman
1966 Victor GP
1967 Victor Special
1968 Victor Special
1968 A65L

2009 HD FXDC
Re: A65 Head interchangeability? [Re: Gordo in Comox] #360612
03/01/11 12:23 am
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Gordo-

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

Rusty


1967 A65 Lightning
1967 Triumph T20 Mountain Cub
1967 Moto Guzzi V7
1969 B44 Victor Special
1966? Royal Enfield Interceptor
Re: A65 Head interchangeability? [Re: Gordo in Comox] #360618
03/01/11 12:51 am
03/01/11 12:51 am
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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


Without frequent roadside repairs there is no fun in riding!
Re: A65 Head interchangeability? [Re: Gordo in Comox] #360712
03/01/11 3:52 pm
03/01/11 3:52 pm
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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
Re: A65 Head interchangeability? [Re: Gordo in Comox] #360718
03/01/11 4:24 pm
03/01/11 4:24 pm
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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


Without frequent roadside repairs there is no fun in riding!
Re: A65 Head interchangeability? [Re: Gordo in Comox] #360719
03/01/11 4:54 pm
03/01/11 4:54 pm
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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:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.
Re: A65 Head interchangeability? [Re: Gordo in Comox] #360722
03/01/11 5:11 pm
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Alex: Thanks for the info.

Gordo


Without frequent roadside repairs there is no fun in riding!
Re: A65 Head interchangeability? [Re: Gordo in Comox] #360822
03/02/11 2:30 am
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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.


1967 BSA Wasp
1967 BSA Hornet (West Coast Model)
1967 BSA Hornet (East Coast Model)
1968 BSA Firebird Scrambler
1968 BSA Spitfire Mark IV
Re: A65 Head interchangeability? [Re: Gary E] #729436
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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.

Re: A65 Head interchangeability? [Re: Gordo in Comox] #729451
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Easiest is also best in this case. Cheers PRT


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