A65 VALVE SPRING LENGTH.

[johnjag]

Hi all - recently bought a 1964 A65 Rocket A65 with a blown head gasket but ran fine otherwise. Took the head off and tested the valves for leakage - poor! So removed the valves to find every inner spring broken. I ordered a new set of Hepolite springs and noticed the new springs were very much longer than the removed originals. The new ones were 2.06" long. the originals 1.692" long, too much for it to be just wear. This of course would lead me to realise why the inners had broke. That is until I looked at my original BSA INSTRUCTION Manual which gives the outer spring free length at 1 and three quarter inches which matches the length of the removed springs. The Haynes Manual gives the free length at 2 and one thirty seconds of an inch and my original BSA WORKSHOP Manual gives the same. So is the longer size of spring correct and the ones fitted are wrong and the length given in my INSTRUCTION Manual is also wrong. All the lengths of the internal springs are given as the same as originally fitted and newly supplied.
Thanks
John.

[Bess]

Hi,
   You need springs parts numbers 40-0169 inner and 68-0475 outer, years 1963-65, sizes as per image.

Many suppliers will offer the part numbers but with the wrong length, the wrong amount of coils or the wrong wire diameter.  This is worth a read:

https://www.classicbritishspares.com/blogs/news/bsa-valve-springs-that-coil-bind?_pos=3&_sid=ae8cf7839&_ss=r

SRM in Wales had the best, it maybe worth giving them a call.

Best wishes...

[johnjag]

Thanks Bess - I am now beginning to think the shorter springs are correct as they won't get coil bound having less coils and less compression. However I am still wondering why all the inner springs have broken.
John.