The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Radlan2 on 27.12. 2019 13:06
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Hi Folks
Further to my posting on the introductions page I have a question. I have gathered together parts to build a short stroke twin using an A7 crank with A7 (Daytona) thick flange barrel which has previously been bored for A10 pistons and drilled for through bolts. My question is:-
To through bolt this setup I need to tap new holes in the crank case, before that I have to find suitable studs, with (ideally) rolled threads made from EN16T, or is there a suitable/ better solution using for instance a Volkswagen or other cylinder head bolts which might require an M10 thread in the crankcase? Interested in any info on how this was done back in the day.
Best Regs
Chris P
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G'day Chris.
I have both my A10 Cafe and A7 Plunger through bolted.
https://www.a7a10.net/forum/index.php?topic=1806.msg12343#msg12343
I'd be interested in seeing pictures of your barrels and where the holes are located.
Cheers
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Hi Muskrat, folks.
A few pics of the barrel which is bored to 71mm, the original (cylinder head) tapped holes were plugged in 4 positions using aluminium, an odd choice? then re drilled all the way through the base 0.377"dia, compared with an original barrel stud hole 0.332". The pitch across the barrel is 6 9/16" the pitch front to back is 2 7/16" I have measured this with a steel rule only, there is a discrepancy of 0.020" on the F/B pitch but it appears true and a pretty good job.
I will simply use the barrel as a drill jig and spot through, into the crank case/head. In order to use 3/8" Dia studs I must open up the existing barrel through holes by at least a further 0.020" for clearance, not how it was envisaged in the original mod. If I use 5/16" studs, well it feels a bit small dia when it will need to be approx 5 1/2" long plus thread. This is why I would like to find a suitable long bolt used in a similar application to then modify, though the problem could then be that such a bolt requires rolled threads. Dunno.
Interested in any thoughts
Chris P
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G'day Chris.
Looks pretty much the same as mine. I used VW through studs but reduced the end into the cases to 5/16" and used helicoils as there's not a lot of meat there.
Lani at Coppergasketsunlimited has the drawing for the head gasket https://coppergaskets.us/
Where did you get it? I know Dan daughenbaugh (forum member) over in the states did it to his land speed record bike a few years ago.
Cheers