Originally Posted by JMo (& piglet)
As John explains above, the combination of a longer rod and adjusting the position of the crank pin will give the necessary stroke to retain the standard bore/cylinder etc. As he explains,the trick[y bit] will be to create a piston profile that creates enough compression while at the same time misses the valves when they are extended - the 690 Rally cam (which should help boost power) has a longer overlap than the stock cam, so things could be a bit tight in there - hence the prototype build and bench test before we go to production with the final specification...
Seeing your using the same compression height as the stock piston,
and using a longer connecting rod, with the shorter stroke.
this will change your rod ratio dramatically.
With this combination it will like a smaller port volume.
Thats why i did this
Good piston guys like,
Venolia, BME, etc etc
Those guys can copy your combustion chamber shape,
upload that profile into the C&C and then can machine the crown of the piston to suit.
It saves alot of time than the old days.