AN Acquires Thruxton Club Racer

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Do Mahle supply pistons for Norton Commandos ? Are Omega piston blanks forged ?
 
Blanks are forged on a new die designed and made by Omega for AN. The forged 750 piston with pin, rings and circlips is 6g heavier than the standard GPM piston. 850 pistons have been forged and will be final cut in the new year.
 
Steve, the piston pictures are from this thread about my short stroke rebuild. There's a little more info on them in the thread.

https://www.accessnorton.com/NortonCommando/short-stroke-750-build.5160/#post-54374

Ken

Thanks Ken, yes I knew the picture originated with you. I just might have a look for the ones I have soon and post a picture. They are original '70s and unmachined so a slightly different shape around the squish area.

'70s Omegas for the short stroke were cast, and reasonably light.

Des Senior and his engine developer had some Omegas made to their own design for a short stroke project in something like 2008.
 
Hi Steve, I posted a picture of the original Omega cast short stroke pistons that I started with on this page. Are they the same as the ones you have?

https://www.accessnorton.com/NortonCommando/short-stroke-750-build.5160/page-2

The only problem I had with them was breaking through from the valve cutouts to the back of the top ring groove. But that was only because I used a head with even larger valves than the original RH7 head had, and also pushed the pistons up further into the combustion chamber to get the CR up. Machining the valve cutouts for that was a bit more than the pistons could take. They actually worked ok for racing for quite a while, but finally burned through into the ring groove. That was the first pair I used. I was a little more conservative when I replaced them with the second set. For the pistons I had JE make, I lowered the top ring groove a bit to avoid the problem.

Ken
 
I would have thought the forged pistons would be lighter than cast ones. Every forged piston I have seen has had very thin skirts. I saw a Mahle piston which had been run so loose that the bottom edge of the skirt had curled under without cracking.
 
Hi Steve, I posted a picture of the original Omega cast short stroke pistons that I started with on this page. Are they the same as the ones you have?

Ken

Yes, they are like that. There were used with standard Commando rods, as they had been machined with the smaller pin hole. I had never considered if the deck height had to be different to cope with a different rod length! For me it all fitted together with sufficent clearance, as tested with 'plasticine'.

But as far as I know a batch of these was delivered to Thruxton.

When I got them it was with a complete kit to build an engine, which the seller had intended to build for himself, before he was laid off.

(As an aside, he then went to work as mechanic for Alex George, which I assume was a fun thing to do in '76! Alex had been riding the Cosworth Challenge in '75, but went on to the 500cc world championships.)
 
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