A65 pistons

[Mike Farmer]

 

I am now building an A65 engine the pots are at +040" and I have a new set and a used set of 9.5:1 pistons. the used set is within very sensible wear limits. About .004"--.006" in the bores

I also have a set of used std 7.5:1 pistons.

I want to use 7.5:1.

+040" 7.5:1 are extortionate as there appear to be none in the UK. (I've just fitted a pair to a bike in rebuild and its come out at +£360 actually EU311 plus vat and shipping £72. Yuk

My thoughts are-----using the std pair as a crown pattern I shall machine one of the other pairs to the same crown profile. I'm sure someone will have done this or something similar.

Your thoughts pleeeze

Mike

[DAVE BRADY]

Hi Mike,

Are the crowns on the 9:1s thick enough to take down to 7.5:1?  A piston with that much material is heavy and top heavy so I think they are all pretty much the same weight with variations by manufacturer rather than much variance by compression ratio.
You may end up with a crown that is too thin.

Dave.

[Mike Farmer]

 

Hi Dave

I had wondered about that and reckon that I can get some accurate internal measurements. Thanks I'll let you know.

Mike

[Mike Farmer]

 

Just followed this thro and measured it, I don't think its viable simply because of the crown thickness.

Mike