This is an original 'Niew Old Stock' Hepolite 79mm +0.020" (500cc) 16H piston - unopened for 70 years! Can also be fitted to SOHC machines as well - Read detail listing. Very limited stock!!
20/4/17: I have been lucky enough to purchase a small batch of original 'New Old Stock' WD Norton 16H pistons, Hepolite Ref 8617. Most are in 79mm + 0.020 oversize, but a couple are +0.030, this listing is for an +0.020, but add a note if you want one of the +0.030 pistons instead - and we will email back if any are left.
These pistons all came in their original box's (now looking very shabby and dusty - but still intact) and were unopened. I have broken the seal and opened each piston to check for condition and corrosion. They may come with slight surface corrosion on the rings or pistons walls - but I have checked on each one that the piston rings all move in their ringlands and removed any light 'furring' to the aluminium, where they were in contact with the corrugated cardboard they were wrapped in. Each piston has then been sprayed in Duck Oil to protect it, re-packaged in the original packaging and then placed into a plastic clear bag for storage.
Each piston comes complete with the original Gudgeon pin and Circlips, as well as the original packaging - they even have the small WD Hepolite packaging slip of paper, an amazing time warp piston.
I have checked each piston and think they will still be perfectly good for use (I have removed two pistons which were not good enough to sell - one had a locked ring in groove, which broke and another was fine, but had some corrosion on the gudgeon pin). Any slight surface corrosion on the rings should wear away as soon as the engine starts (as often is the case with any engine that has not been run for a few months).
These pistons are good quality 'full skirt' type Hepolite pistons originally fitted to pre-war and WD type Norton 16H Sidevalve engines. However, to my knowledge the only difference between these and the same period (i.e. pre-war) Norton OHV Model 18/ES2 piston was a slightly higer compression ratio, as a result of a slightly raised dome, and of course there would have been slight indents in the crown of OHV/OHC engines for valve clearance. Many years ago in the mid 1980's I used one of these pistons in a petrol ES2 race engine, having knife edged and relieved the bottom skirt and found them to be an excellent piston.
At some time in the future I will be re-ordering the high compression Omega Forged racing pistons for SOHC petrol (non-alchohol) engines (Item No 0396 -0398), but due to the high investment needed for a batch this may be some time yet. Therefore, if you have an OHC or OHV engine on the road (and not intending to use it for for heavy high speed or racing use), then these are viable alternatives. You will of course have to check the valve clearances, particularly if the barrel is skimmed to raise compression ratio - but to mill/cut slight valve indents in the crown is a relatively simple task for anyone with a vertical mill (or even careful use with a small diameter angle grinder) - I have milled small valve cuataways in these pistons myself in the past, and seem to remember it being a simple job.
Final note on Dimensions: Distance from top of the Gudgeon Pin circumference to the Outer Crown - 23.2mm. Height of Crown from outer crown to the centre of the crown - 11.5mm. Distance from the bottom of the Gudgeon Pin circumference to the bottom of the skirt - 28.6mm (it is worth checking your own flywheel assembly/Little End Eye at bottom of the stroke to check that the skirt does not fould the flywheels at the bottom of the stroke - although again, it is a simple task to remove the lower skirt at the side in a curved arc if there is any risk of fouling - again I have done this in the past when fitting it to 'tall type' ES2 flywheels).
Alternatively if you have a Norton 16H Sidevalve Norton - this is the correct and original piston!
Only a very limited stock, when they are gone they are gone!- your chance to own and fit an original 'NOS' Norton piston in your machine . . . not sure if you will ever find one again