The head on my Bonnie (in this months issue of real classic - co, I'm famous!) has got valve seat recession on one(!) valve. Seriously thinking about getting an 8 valve head for her. Anyone know what else needs changing - fit and forget?
She doesn't really need to be any faster, but she always feels a bit strangled at the top end, plenty of torque so I just ride the waves. Just time for another evolution I think.
Triumph also did an eight valve head for a while on the 750 TSX towards the end of Meriden.
I've no idea of what else needs changing but I would imagine that a Weslake head includes rocker boxes and rocker arms and shafts? I can't imagine setting twice the number of valve clearances through the circular type tappet inspection covers that were on 650s up to 73/74. They must at least use the rocker covers with the larger, single, oval type cover on each side, or come with the head?
I'm sure you're aware that your existing head can probably be fixed even if the valve seat is very worn and there are cracks to the stud holes?
Paul - TSX was a styling exercise the 8 valver was TSS. Never had one myself but knew a few tha did when they were new.
TSS had a different stiffer crank. Different rods and used 2 rings instead of a normal head gasket
The whole layout on 8 valvers was quite a bit different.
Valves were set at a more upright angle and used shorter rockers forked to drive 2 valves each. The push rods were angled out a bit I think and the rockers were the other way round - if you see what I mean - push rods on the outer end and valves on the inner end.
IIRC the valve adjustment cover was the whole top of the rocker box.
Good TSS was quite a bit quicker than a T140E and a lot smoother too.
Some who had TSSs thought they were the dog's bollox and others thoutht they were a load of bollox. There were good ones and bad ones. The Co-op were about out of money and a lot of stuff went out to customers that should have gone in the skip. There were quite a few porous head castings got used among other problems.
You would also need to modify the crank casings as the TSS 8 valve engine had oval push rod tubes. Your standard T140 casings would have to be machined to accomodate the push rod tubes for a TSS type head.