- Joined
- Jan 18, 2012
- Messages
- 130
Hi
I have a Combat engine,
when I rebuild it, I've decided to detune it and I fit a standard cam and an RH1 head.
I fit also a new pair of hepolite pistons,
If I would back to Combat spec, (I know I have to open it to replace the 2s cam)...
But the question is, what about the pistons?
does the new hepolite pistons fit with a Combat Head?
I know Combat pistons where introduced with bigger valve recess on the top, is it correct?
I have read a post from Icrken
"in 1972, all Commandos, standard and combat, intially used what Norton called an "Interim" piston design, part numbers 063338 and 063339. The only difference from the previous standard pistons, part numbers 062459 and 062462, was deeper valve notches in the piston to accomodate the combat cam lift profile . The interim pistons were installed starting with engine number 200976. These pistons still had the slots in the oil ring grooves. Starting with engine number 204166, Norton installed the "final 1972" piston design, part numbers 063348 and 063349, in all Commandos, standard and combat. These pistons also had the larger valve notches, but had solid skirts. They were used for all the 750 Commandos from then on. Both the interim and final designs were for a nominal 9.0 compression ratio, had the same deck height, and were considered interchangeable by the factory. The combat got it's higher compression by milling the head 1 mm/.040". The combat engines did not have higher compression pistons from the factory, and they should have the same deck height as standard Commandos. All this info is from the Norton factory service releases"
Best piston for a Combat engine to buy new?
Please advice
Mario
I have a Combat engine,
when I rebuild it, I've decided to detune it and I fit a standard cam and an RH1 head.
I fit also a new pair of hepolite pistons,
If I would back to Combat spec, (I know I have to open it to replace the 2s cam)...
But the question is, what about the pistons?
does the new hepolite pistons fit with a Combat Head?
I know Combat pistons where introduced with bigger valve recess on the top, is it correct?
I have read a post from Icrken
"in 1972, all Commandos, standard and combat, intially used what Norton called an "Interim" piston design, part numbers 063338 and 063339. The only difference from the previous standard pistons, part numbers 062459 and 062462, was deeper valve notches in the piston to accomodate the combat cam lift profile . The interim pistons were installed starting with engine number 200976. These pistons still had the slots in the oil ring grooves. Starting with engine number 204166, Norton installed the "final 1972" piston design, part numbers 063348 and 063349, in all Commandos, standard and combat. These pistons also had the larger valve notches, but had solid skirts. They were used for all the 750 Commandos from then on. Both the interim and final designs were for a nominal 9.0 compression ratio, had the same deck height, and were considered interchangeable by the factory. The combat got it's higher compression by milling the head 1 mm/.040". The combat engines did not have higher compression pistons from the factory, and they should have the same deck height as standard Commandos. All this info is from the Norton factory service releases"
Best piston for a Combat engine to buy new?
Please advice
Mario
