The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Nourish on 31.01. 2014 22:43
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I've just received some thick flange barrels off e Bay but they won't sit in my BA7 crankcases - it looks like the spigot is fouling on the piece of crankcase between the mouth and the cam follower opening - is this usual - should I relieve the barrel spigot or the crankcase?
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A picture is worth a 1000 words, as they say.
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Never had this problem putting thick-flange barrels on plunger cases, but If I did, I'd definitely be relieving the crankcase not the barrels.
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Not A65?
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A10 Barrels?
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They look like A10 barrels to Me ?
I have never seen A65 ones however so cannot comment with certainty .
Perhaps You could photograph the flange view for confirmation ?
Steve ...
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You could photograph the flange view for confirmation ?
and the op of the crankcase
I'd say A10 defo as well
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I have an A65 and they are definately not A65.
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No two sets of cases are 100% the same. It's just the way castings were machined back in the day.
Adjust the cases not the barrels.
Cheers
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That's two of you who say to relieve the cases and not the barrel - as it's under the flange and not where they usually break - Why?
Hope you can see where I've marked where they are contacting
Cheers
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The skirts of the barrels are thin enough. I've seen them brake off without too much provocation.
The cases won't be weakened by a little grinding there. I had to do similar to a set of CA7 cases.
Cheers
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Well, I think this photo of my crankcase may answer the question. As you can see (and as I had never noticed before) the crossmember is relieved in the same place Nourish's/your's will be. It seems to me that the reason relieving the member ( *whistle*) was not previously necessary is that this is the first time the larger bore A10 barrels are being used on the A7 cases.
I have a frustrating, but now over, side note to this. In looking at crankcase diagrams, I noticed the alignment dowel in the crossmember. Before putting the cases together, I had forgotten to confirm the dowel in place. This meant disassembly, to be certain. Luckily, it had not been so long that the joint sealer had set, so the job was not horrible, but an hour of my life not coming back. The dowel was there.
'
Richard L.
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You could probably do without that dowel. The cases align via the register around the circumference of the mating surfaces. This ensures the alignment of the main bearings.
As long as the barrel flange is then properly flat they would be OK.
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A little hard to see in this pic....
but my A10 cases have been releived of some metal at some stage like Richards,
I always wondered why.... now I know.. *smile*
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The look of the relief in Wozza's/your crankcase is very similar to the work in mine, which makes me think this was factory done.
Briz, I'm sure you're right about not needing the dowel for case alignment, but I was done by the time you wrote. Anyway, I was concerned that the dowel was also intended to provide an added element of stability for the slim crossmember. The fact that it's part of the breather path is probably not an issue.
Richard L.
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Funny that this should occur, given that the cases for A7/10 are the same.....aren't they....?
Richard I had in mind the breather gallery, but you headed me off... ;) I believe the dowel should be there, with sealer, as without it provides more potential for oil to leak out the breather pipe...as sometimes comes up in topic...?
Another thing to keep in mind is ensuring the nut on the stud above it is tight- I had to open mine up at least twice to check, even though right before I did it first times was completely focused on task....out of sight-out of mind...(yes Bill)*eek*, but at least a barrel off is not as bad as a case splitting..... *ex*
(reason for 'twice+' was because there was a noise I had to isolate- hence stripdown)
cheers
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I didn't think about the oil leakage possibility through the breather, so sealer at that part of the joint is haphazard. We'll see about breather oil leakage. I'm sure as hell not parting it again for that. Anyway, the original design was not intended to include sealer on that joint, as I understand it.
The cases are the same, but my understanding is that Nourish bought A10 barrels to go on his A7 case.. Interesting to note that the cutaway in the crossmember is only on one side, and the same side, in both of the examples shown. A matter, I think, of "easier to trim the case than fix the mold pattern."
Richard L.
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The A7 and A10 cases are the same. Some do, some don't problem is due to the way the virgin castings are machined. A rough surface is fixed to the machine table and a face of the casting is cleaned up. Then most of the machining is done relative to that. So if in the original set up there is a bit of sand or irregular lump on the casting the end result will be slightly different to the next casting.
My first job after apprenticeship was machining gearbox castings for elevators.
Cheers
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I found my two thick flange barrels had slightly different overhang at the back, with the one I had shortened by 1/2" (for short rods) interfering with the magneto *sad2* so that over hang got milled off, so my mag now fits.
My road rocket cases also had inadequate clearance in the cam shaft trough to run a 357 cam without minor milling.
As soon as you start mixing and matching you can never guarantee its simply a matter of bolting on. and don't get me started on fitting a Joe hunt mag *eek*
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back in "the day" every thing was made using auto lathes & mills that machined between stops or against a cam.
Production tooling was high carbon steel which as all you who machine knows dulls or picks up alloy ( some times both ).
Thus no two parts would be machined identical.
The trick was to measure every thing using go-no go gauges and fit the best available part.
This is why you see all those strange little marks, numbers or letters stamped all over the place.
If the "f" gauge went into the hole, it got "f" stamped into it so the assembler took a shaft out of the "f" box and fitted it to the motor.
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If the "f" gauge went into the hole, it got "f" stamped into it so the assembler took a shaft out of the "f" box and fitted it to the motor.
gotta love them 'F' gauges and shafts... *smile*
I must've got lucky, the 357 fits my plunger cases ok, though there is a barrel overhang that I wondered about but causing no grief at this stage...!
*beer*
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had to do the same with mine..i am using 51 cases and found a set of big fin barrels...
had t get out the big file...and cut just as in all the pictures