Con Rod Length

Only one length ex factory, today the hot setup is short low weight piston on a long con rod to keep piston height the same.

John:

Your posting talks about a "long con rod"

So, you are saying that there were in fact long and short(er) con rods?

Mike

No ex factory in the day but one length, but there are now.

MAP do one version, Thunder Engineering do another but you need matching high pin short pistons to keep standard barrel.

Bill

the Norman White build may have used something like the Jim Schmidt Motorsport offering from the USA. Probably the best known and used kit among racers etc and beneficial on iso or solid mount bikes. His products are superb quality and well developed. I settled for standard length Carrillo steel rods and forged JE pistons for my Commando build, back when Carrillos were £388 a pair

This link provides a good amount of info on the subject

https://jsmotorsport.com/js-motorsport-technical-pistons-and-rods/

FWIW, years ago I acquired a pair of Cosworth pistons for a Commando engine I intended building. As well as reworking the head and machining out the Concentrics to 33mm (at his suggestion), Mick Hemmings had the 850 barrels bored out to suit the oversized pistons.

As the Cosworth gudgeon pins were larger, when we discussed machining the small-ends, Mick said best thing would be to bore them excentric, so as not to take any meat from the top of the rods.

Never got round to the job, and subsequently sold off the whole top end, so I cannot say what the effect of reducing the centres was, but I guess 1-2mm wouldnt have made that much difference on a road bike....