The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: 0116harley on 05.02. 2012 11:46

Title: cylinder head
Post by: 0116harley on 05.02. 2012 11:46
Hi everyone
Thought id do some work on my A10 this weekend. Just putting the rocker cover back on when one of the long bolts snaped of in the head (some times its one step forward an 3 back on this bike). Anyway as im trying to remove the bolt with a bolt extractor i noticed a crack im sure this is not going to affect anything but would like to no what you guys think.
Also can anyone tell me what thread the bolts are i think there 5/16 bsf
cheers neil
Title: Re: cylinder head
Post by: Beezageezauk on 05.02. 2012 12:19
Hi Neil,

If the thread is still original it will be 5/16 x 26tpi cycle thread and the original bolt was 3 1/2 inches long.

Obviously you don't want any cracks but I don't suppose that it will harm if the crack is not too bad and you think that the pressures on the rocker box won't affect it too much.   Use it as is, keep your eye on it and check for oil leaks on a regular basis.

Beezageezauk.

Title: Re: cylinder head
Post by: Goldy on 05.02. 2012 12:55
If the crack is through the tapped hole then there is no use putting a bolt in it and as these bolts hold the head steady bracket I would think that is going to lead to problems. Whilst you have it strippped down take the head off and get it welded is what I would do. all the best Goldy
Title: Re: cylinder head
Post by: trevinoz on 06.02. 2012 19:46
The head bolts are not 26 tpi but BSF as you surmised.
     Trev.
Title: Re: cylinder head
Post by: bsa-bill on 06.02. 2012 20:08
I thought the subject was Rocker box studs
Title: Re: cylinder head
Post by: trevinoz on 06.02. 2012 20:10
Bill,
         My mistake, just out of bed and eyes not working properly, or maybe the brain.
       Trev.
Title: Re: cylinder head
Post by: 0116harley on 06.02. 2012 20:21
Hi all
   never welded cast iron before heard its a right pig to weld, so dont surpose its any good geting the mig out an givin it ago
cheers neil
Title: Re: cylinder head
Post by: wilko on 06.02. 2012 21:54
It's easy to migweld cast iron. I've filled in  an M20 head to give it some go. (http://i244.photobucket.com/albums/gg3/takka22/000_0894.jpg)
Title: Re: cylinder head
Post by: bsa-bill on 06.02. 2012 22:10
know what you mean Trev, lasts most of the day at my age though.

Now then welding cast. bound to be some members here skilled in doing that so I stand to be corrected but we used to heat the job first to cherry red then weld it with a stick for welding cast, of course mig is a different thing, can you get mig wire for welding cast
Title: Re: cylinder head
Post by: Brian on 06.02. 2012 23:20
Recently I had some fins to repair on a cylinder and thought I would give the mig a go just to see what happened. Absolutely brilliant, I used normal general purpose wire and stitch welded them about 1/4" at a time. Probably the best cast welding I have ever done. I used to use a stick welder with high nickel rods.

I would have no hestitation in welding a crack like that in a head with the mig. Blast the crack area clean and then V it out and weld in in three or four goes.
Title: Re: cylinder head
Post by: 0116harley on 07.02. 2012 09:30
Hi Brian im tempted to have a go with the mig. What size wire did you use, think ive got 0.6 in my welder.Did you let it cool down between each weld
Title: Re: cylinder head
Post by: Brian on 07.02. 2012 09:34
I've got .06 in mine and that is what I used. I welded about 1/4" at a time and let it cool for about 5 minutes. I did have to use slightly higher amps than normal.

I would recommend having a go on a bit of scrap first.
Title: Re: cylinder head
Post by: TT John on 07.02. 2012 10:46
Brian. what was thee outcome on the M20 head did it improve performance by much? also was it noticable?.

Regards TTJohn
Title: Re: cylinder head
Post by: wilko on 07.02. 2012 21:26
It was me. Yes it certainly gave it some guts. An extra 10 mph! It out drags a C11 now! Goldy cams next!
Title: Re: cylinder head
Post by: TT John on 08.02. 2012 09:08
Wilko.
Sorry mate, got the posts mixed up. Must learn to read proper next time *eek*.

Regards TTJohn *smile*