The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: chaz on 21.03. 2013 17:54

Title: head and bores questions
Post by: chaz on 21.03. 2013 17:54
before I start re ringing Ive a couple of questions...
firstly looking at Roy Bacons book the cylinder head for a 1952 plunger A10 should be 67-1065, mine is a 67-1066 any difference??
second, bore with new rings have 0.015" end gap is this right/ wrong as cant find spec at the moment.
thirdly , Draganfly have sent Gandini rings. are these ok, or not?
fourthly , having just rebuilt an ariel square four motor on standard original pistons the Gandini rings wouldnt fit in the bores, after much cussing and phone calls its established the inner diameter of the rings is 0.020 smaller than standard/Hepolite ones, will I have a problem?
reason for asking is that the square 4 caused a lot of trouble and if I dont need to re ring or bore then Ill keep them until I do unless I am going to get trouble fitting them... Gandidni aka GPM, thanks
Title: Re: head and bores questions
Post by: bsa-bill on 21.03. 2013 18:19
Quote
A10 should be 67-1065, mine is a 67-1066 any difference??

Casting number 1 different then part number
ring gap - don't know if there's a difference with plunger engines but for mine (59 s/a) 13 thou compression rings and 11 oil control
Plunger owners here will have more appropriate knowledge so ignore mine if they say different.

I have GPM pistons in mine no problems so far

some info here http://www.bsawiki.com/index.php?title=Chapter03 (http://www.bsawiki.com/index.php?title=Chapter03)
Title: Re: head and bores questions
Post by: wilko on 21.03. 2013 22:11
Always check ring depth on all piston sets. I have a high comp piston for my Matchy single that had a top ring groove shallower than the other two!
Title: Re: head and bores questions
Post by: TT John on 22.03. 2013 14:06
Chaz.
I know that the heads are different on a s/a A10 to a plunger. not sure what the casting number is but on my plunger A10, I have fitted a head which was for a s/a, (the plunger one is more rounded) but I had to cut down the carb manifold so that I had room to fit the carb in, before that, I had a Ariel Huntmaster head but that again was slightly different in that I had to get Hunt master exhaust pipes as they are flange fitting also come out at a different angle.

TTJohn
Title: Re: head and bores questions
Post by: chaz on 25.03. 2013 19:17
thanks for the input, had problems with the gpm's and my reborer hates them
Title: Re: head and bores questions
Post by: bsa-bill on 25.03. 2013 21:32
last rebore I had done the guy said he'd give it an extra half thou as they were GPM pistons.

Now read that again while considering I was taking the barrels back to him after his previous rebore (100 miles previous) as the original pistons (Australian) showed signs of picking up around the crown, which he reckoned was grit !!!!!