hi to all first ever post so be gentle! Just rebuilding a 67 hornet and i have just come across some lovely barrels with thier 20 over 10.1 pistons. Theres adifference in that the stud holes are 3/8 and the original studs are 5/16. Can i make up spacing sleeves or would it be better to re stud the cases? Any advice would be appreciated. Thanks for this font of knowledge.j
Hi Dibble,
Welcome to the Forum. It is probably worth upgrading the studs as this is what BSA did and especially for 10:1 compression. SRM is probably a good place to look as they will do the studs and I think I have seen tap kit for them as well. I am sure that sleeving the barrels would work but personally I would always have that bit of doubt in the back of my mind.
Dave.
I think that the 3/8 inch studs came in for 1970. The 1970 barrels had a revised stud spacing and cutouts in the bottom fin so they dont interchange with the earlier barrels.
Hi,
It looks like SRM's big bore kits fit the earlier and later cases but the earlier ones need the stud conversion.
From SRM website
"Suitable for BSA A65 1970-72, 1962-69 will need to select the 5/16" - 3/8" base stud conversion kit in the options above"
This seems to imply that the only difference is the dia. of the studs?
Dave.
Thanks Dave for the advice. I know what you mean about the "doubt" think and thats why im going for the upgraded stud option. It makes you think though the hornets of the day did ok on the 5/16 as standard, i think! I've investigated the barrels and the only difference seems to be the stud holes. The casting numbers are still 68.44 as per the originals. Thanks all.
Hi Dibble,
Prompted by Julian's comment re stud centres changed I did a bit of digging. The difference is apparently about 70 thou and some people have slightly elongated the hole to allow the later barrels to fit. I have never seen the SRM big bore kit but guess that they must have an elongated hole to allow for the small difference in stud centres.
If you are going to convert to the larger studs ask SRM what their advice is.
Dave.