Model 7 pistons

Previously howard_robinson wrote:

Hiyah Marcus - Depending on the year and assuming that you're using the standard iron cylinder head the original fit pistons would have been 6.7:1 compression ratio or latterly with the better quality fuel 7.8:1. The part numbers of these were D12/702 and L12-2/702 respectively. The Hepolite 7.8:1 (19785/6 ) would be a good substitute or even the Hepolite 8:1 (22504/5 ). These were the standard fayre for a Model 88 but they use the alloy head which is probably higher compression than the iron head. So these would be OK. You may even use the 8.5:1 (23179/80) subject to availability but I wouldn't go with the 9.0:1 or 9.45:1 88SS pistons. You'll probably have quite a search to get what you need so start with the American and European dealers. Good Luck, Howard.

Hi Howard,

thanks for that, mine is a 54 and has an alloy head, I'll try Norvil , andover and rgm monday, see what they have, looks like more searching

Thanks Marcus.

Previously anna jeannette Dixon wrote:

Previously marcus_bloomfield wrote:

Previously howard_robinson wrote:

Hiyah Marcus - Depending on the year and assuming that you're using the standard iron cylinder head the original fit pistons would have been 6.7:1 compression ratio or latterly with the better quality fuel 7.8:1. The part numbers of these were D12/702 and L12-2/702 respectively. The Hepolite 7.8:1 (19785/6 ) would be a good substitute or even the Hepolite 8:1 (22504/5 ). These were the standard fayre for a Model 88 but they use the alloy head which is probably higher compression than the iron head. So these would be OK. You may even use the 8.5:1 (23179/80) subject to availability but I wouldn't go with the 9.0:1 or 9.45:1 88SS pistons. You'll probably have quite a search to get what you need so start with the American and European dealers. Good Luck, Howard.

Hi Howard,

thanks for that, mine is a 54 and has an alloy head, I'll try Norvil , andover and rgm monday, see what they have, looks like more searching

Thanks Marcus.

Hello Marcus now the real pistons fitted to Norton twins were BHB -Rolls Royce and Hepolitecopied them and so did JP pistons along with Giardini pistons of Italy has Giardini Pistons known hasGPM is all you get in our days unless you're preparedto wait and do your research untilyou find a suitable set for your machine they are out there you just have to keep looking . and 8.5.1 is about the best all around has high compress with ethanolfuels may cause pinking and burning of the valves, have fun yours anna j Dixon

Hi again may have a lead on some BHB, if not i guess Giardini, with extra tolerance?