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T100 Engine Cases

2K views 12 replies 5 participants last post by  Norcoastal 
#1 · (Edited)
Are they the same?

I have a 1968 T100R and I need half of a case. There seems to be a lot of T100C's but not a lot of R's.

I know the juggs, pistons and heads are different, but are the cases interchangeable?

Thanks
 
#4 ·
Were the cases machined as a set at the factory so that the crank and cams ran true? I seem to remember something about that from years back. If so, it's something that might have to be considered.
But, then again, the "village idiot's" memory is fast becoming just that: Jim
 
#5 ·
Hi,

I have a 1968 T100R and I need half of a case. There seems to be a lot of T100C's but not a lot of R's.
are the cases interchangeable?
they're the same.
Uh-uh ... pre-'69 350/500 crankcase 'halves' might have the same part numbers but they aren't interchangeable - "the same". Jim is absolutely correct - crankcase 'halves' castings were bolted together, machined and then both 'halves' were stamped (on the lower engine mounting) with the same code, to ensure they were reassembled together after disassembly. That's why you read that replacement crankcases were supplied in "pairs" (of 'halves').

You might get a 'half' that appeared to match the one you have, but the pair will require measuring by someone who knows old Triumph twins to ensure main, cam and gearbox bearing housings are true and/or any machining necessary to make 'em so. By the time you've paid for that, you might as well have your original 'matching' crankcase half repaired (as you've asked and been advised already)?

If you're looking for a cheap way of getting a pair of usable crankcases, ... 'fraid there isn't one (otoh, there are several 'cheap' ways of fcuking-up what're currently perfectly good parts). As the saying goes, if you don't have the time and money to do the job correctly now, when are you going to have the time and money to fix a balls-up? :)

Btw, you do know:-

. pre-'69 and '69-on 350/500 bottom-end parts are completely different and not interchangeable at all;

. apart from 350/500 bore differences, "juggs" are interchangeable?

Hth.

Regards,
 
#8 ·
Hi,

I have a 1968 T100R and I need half of a case. There seems to be a lot of T100C's but not a lot of R's.
are the cases interchangeable?
they're the same.
Uh-uh ... pre-'69 350/500 crankcase 'halves' might have the same part numbers but they aren't interchangeable - "the same". Jim is absolutely correct - crankcase 'halves' castings were bolted together, machined and then both 'halves' were stamped (on the lower engine mounting) with the same code, to ensure they were reassembled together after disassembly. That's why you read that replacement crankcases were supplied in "pairs" (of 'halves').

You might get a 'half' that appeared to match the one you have, but the pair will require measuring by someone who knows old Triumph twins to ensure main, cam and gearbox bearing housings are true and/or any machining necessary to make 'em so. By the time you've paid for that, you might as well have your original 'matching' crankcase half repaired (as you've asked and been advised already)?

If you're looking for a cheap way of getting a pair of usable crankcases, ... 'fraid there isn't one (otoh, there are several 'cheap' ways of fcuking-up what're currently perfectly good parts). As the saying goes, if you don't have the time and money to do the job correctly now, when are you going to have the time and money to fix a balls-up?


Btw, you do know:-

. pre-'69 and '69-on 350/500 bottom-end parts are completely different and not interchangeable at all;

. apart from 350/500 bore differences, "juggs" are interchangeable?

Hth.

Regards,
Stuart, wow you have a great memory but I'm afraid you've misunderstood my question.

Maybe I didn't explain myself. While I do need half a case, I am NOT considering using a mis-matched engine case.

What I am asking is are the cases interchangeable. Meaning, can I use a T100C set of cases with T100C jugs, pistons, heads and carbs.

It's hard to find R cases and C cases are easy to find and cheaper.

Can a C case be matched with R juggs and heads.

I'll keep the original engine to sell with the bike but I'm looking to build a motor.

I believe that was actually your suggestion Stuart.
 
#6 ·
While Stuarts advice is absolutely correct, there HAVE been documented exceptions of people installing random replacement case halves WITHOUT re-boring, and were successful.

I recall one mention of eliminating the alignment dowels "helping the innards align" the mismatched case halves. The stuff was all assembled loosely with plenty of oil everywhere, then the case fasteners were slowly tightened while continuously rotating everything, and then finally torquing them down.

Personally, on MY OWN stuff, I could see trying that, "just for grins".
 
#7 ·
Hi Paul,

there HAVE been documented exceptions of people installing random replacement case halves WITHOUT re-boring, and were successful.
I recall one mention of eliminating the alignment dowels "helping the innards align" the mismatched case halves.
On a 'C'-range? Reason I ask is the crankcase halves on my 500 have a 'lip' around the junction; leaving out the dowels would only allow the 'halves' to be rotated relative to one another, not moved backwards/forwards and/or up/down. Rotating around the main bearings risks the crank, cams and/or gearbox shafts don't end up parallel to one another and/or the barrel land has steps in it that require machining the land.

Regards,
 
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