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A65 top end compatibility #39688
06/10/08 7:42 pm
06/10/08 7:42 pm
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gastonia nc
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raf940 Offline OP
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the rolling chassis part of my A65 project is wrapping up and the time to start with the powerplant will be here soon...a quick question on parts interchangeability...i have 1966 A65 cases..will all 650 cylinder years fit? also what years of cylinder head would work.......the one that came with the 'kit' says 71-2200 i take to be an OIF model
many thanks


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
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Re: A65 top end compatibility #39689
06/10/08 8:09 pm
06/10/08 8:09 pm
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Stone Creek OH USA
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Rich B Online happy

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Stone Creek OH USA
All cylinders up to the advent of 3/8" base studs will fit (62 - 69?). If you have a late head, you need cylinders with 3/8" rear bolt holes. Earlier heads/cylinders used 5/16" bolts at the rear of the head.

You need 67 - 69 cylinders based upon the bottom end and head you already have. Just watch, some 69's though have 3/8" base studs.


Life is too short to drink cheap, bad beer.
Re: A65 top end compatibility #39690
06/11/08 1:41 am
06/11/08 1:41 am
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gastonia nc
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raf940 Offline OP
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raf940  Offline OP
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thanks! in other words anything from 66 up to OIF would work for cylinders,,,how do i judge the year of heads??i see some on eBay with a prefix 68..the one i have starts with 71...does that indicate the year??


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 top end compatibility #39691
06/11/08 2:39 am
06/11/08 2:39 am
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Christchurch, NZ
Kevin (NZ). Offline
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I didn't interpret it that way RAF.
'67 to '69 cylinders are required. They will have the 5/16 base holes and the top threaded holes will all be the same size at 3/8.
Earlier varieties will have the two smaller rear holes at the top. The later versions will be 3/8 base stud. (too large for your '66 cases).
I doubt the 71-.... indicates the year.
the same applies to the head, - are all the holes equal sized ? (1967 and on).
The later OIF rocker covers have two extra holes for the head steady.
You may well have a '66 head in which case only pre-1967 cylinders will do the job. (Two smaller rear holes).


Why, Y, Dash Y..



Re: A65 top end compatibility #39692
06/11/08 10:45 am
06/11/08 10:45 am
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Stone Creek OH USA
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Rich B Online happy

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Kevin,

The Triumph P/N system started around 70? 71-XXXX is an engine part no.,, not a year. So I am assuming 70 on head. He will have to work out the rocker cover thing when he gets to that point.


Life is too short to drink cheap, bad beer.
Re: A65 top end compatibility #39693
06/11/08 1:16 pm
06/11/08 1:16 pm
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gastonia nc
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raf940 Offline OP
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i think i have it now..........thanks fellers


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 top end compatibility #39694
06/11/08 3:33 pm
06/11/08 3:33 pm
Joined: Sep 2002
Posts: 7,812
Seattle
Alex Offline

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Alex  Offline

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Seattle
It is, in fact, possible to put the later barrels on an early motor. All you have to do is grind about 1/8" out of the front inner mounting holes and use some grade 8 flat washers under the base nuts. Worked fine for me in the past.

Also, as far as I know, all you have to do is drill out the rear center mount head bolt hole and clearance the pocket in the head for a socket to use an earlier head on a later barrel. I don't see why a later head wouldn't work on the earlier barrel if you use the 5/16 rear center bolt. All the other head bolts save that one were the same through the years.


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 top end compatibility #39695
06/11/08 3:57 pm
06/11/08 3:57 pm
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Posts: 3,235
arkansas
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leon bee Offline
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arkansas
Alex is my man! I hadn't decided to mention it yet, but I am running a 3/8 rear bolt hole head on an earlier barrel with 5/16 bolts and good washers. No problems, but only a couple hundred miles on that setup. And I am getting ready to do it again on another engine. Then, I been wondering.....why wouldn't you just drill the rear holes to use an earlier head on the 3/8 bolt cylinders. I am, after all, in Arkansas. Then after all that I got a couple of those 71 cylinders I've been pondering putting on 68 crankcase.

Re: A65 top end compatibility #39696
06/11/08 4:12 pm
06/11/08 4:12 pm
Joined: Sep 2002
Posts: 7,812
Seattle
Alex Offline

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Alex  Offline

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Seattle
I really don't think there's anything wrong with doing that. Remember that the extra clearance on each side of the hole is only .030". A .060" thick grade 8 washer won't deflect at all over that gap.


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 top end compatibility #39697
06/11/08 4:45 pm
06/11/08 4:45 pm
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Stone Creek OH USA
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Rich B Online happy

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The 5/16" bolts are longer than the 3/8" bolts. The heads are machined different to accomodate the length. The 5/16" heads have a boss that is not on the 3/8" bolt heads. Yes you can use a 3/8" head with 5/16" bolts, but depending on tolerance stack up, you may bottom the bolts out in the barrel before they tighten the head.

Early heads on late barrels can be made to work, but, you need to machine the boss off and also open up the hole to get sufficient engagement of threads with the 3/8" bolts.

Late barrels on early cases will work also with some effort. 4 regular studs need replaced with the 5/16" doweled studs to fill the gap in the cylinder. Leave the 2 front studs as 5/16" to allow for the difference in spacing of the holes. Replace the 2 existing studs with regular 5/16" studs and make a hollow dowel to make up the difference in size between a 5/16" cylinder base & the 3/8" dowels.

Not that I would do any of the above :rolleyes: . and if I have done any of the above, I will disavow any knowledge of performing said bodges :p .


Life is too short to drink cheap, bad beer.
Re: A65 top end compatibility #39698
06/11/08 8:04 pm
06/11/08 8:04 pm
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gastonia nc
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raf940 Offline OP
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alex..i hope in a while when i get ready to do the motor that i can hire you to do the bottom end....ok?


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 top end compatibility #39699
06/11/08 9:35 pm
06/11/08 9:35 pm
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gastonia nc
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raf940 Offline OP
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ok.....i got home from work and measured the studs in the cases..they are 5/16.....all of the holes in the head are 3/8 .i dont have cylinders yet but am assuming i can use the head with any one of the above 'fixes' on what might be procured in th eway of cylinders


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 top end compatibility #39700
06/11/08 11:23 pm
06/11/08 11:23 pm
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gastonia nc
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raf940 Offline OP
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raf940  Offline OP
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well a guy just told me he had a cylinder with 3/8 base holes and i could just remove the 5/16 studs from my cases and retap for 3/8 ones...whadda ya think about that?


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 top end compatibility #39701
06/11/08 11:33 pm
06/11/08 11:33 pm
Joined: Sep 2002
Posts: 7,812
Seattle
Alex Offline

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Alex  Offline

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Posts: 7,812
Seattle
Quote:
Originally posted by raf940:
well a guy just told me he had a cylinder with 3/8 base holes and i could just remove the 5/16 studs from my cases and retap for 3/8 ones...whadda ya think about that?
It's not QUITE that simple. Yes, you can bore and tap for the larger studs, but it needs to be don VERY carefully to make sure the studs are square to the case. Also, as I mentioned earlier, the front inner studs were moved by about 1/16". I would say unless you're building a racer, the 5/16 stud are adequate.

On the plus side, this'll make the head installation much simpler.

As long as it's after Mid-Ohio, I can put your bottom end together no prob.


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 top end compatibility #39702
06/11/08 11:52 pm
06/11/08 11:52 pm
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Posts: 3,664
gastonia nc
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raf940 Offline OP
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raf940  Offline OP
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gastonia nc
i think i'll stick with the 5/16" studs........i have fork tubes, rim, and spokes coming this week then off to gettysburg for the july 4th weekend extravaganza so i'll be busy a while myself...i printed out the suggestions above and will study them in the meantime


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 top end compatibility #39703
06/27/08 9:27 pm
06/27/08 9:27 pm
Joined: Mar 2006
Posts: 3,664
gastonia nc
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raf940 Offline OP
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raf940  Offline OP
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call it blind luck or whatever...but i got a nice set of cylinders off eBay for $75 including tappets and it had 5/16 base studs and 3/8 head studs just like i needed for the case and thunderbolt head i had...


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

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