RV8 4.6

[Sir Shelby]

Hello all together,
just a short introduction of myself:
My name is Markus, I am living in Germany and built up a Pilgrim Cobra with a Rover V8 3.9 the last 3 years. I got this kit from a guy who bought all the parts in 1991 and never touched them. The car is now running and registerd since spring 2019.
Right now I build up a RV8 4.6 engine for this Cobra and need some technical help.

Pistons/conrods: I want to swamp from 4.6 pistons onto the 4.0 ones in order to reach higher compression ratio
a) are the conrods of the 4.6 and the 4.0 the same ones?
b) I weighted a difference of 20 gramms between the 4.6 pistons with conrods and the 4.0 pistons with conrods. is this just caused by the different deepening in the piston or caused by different conrods?
c) need the crank get rebalanced due to this increase of weight of the piston/conrod combination or is it good enough to equal them?

Thanks to everybody for each advise and help.

Kind regards
Markus

PS: I am sure this won't be my last questions in that project

[garrycol]

Conrods are different (different length) - for a 4.6 you need 4.6 conrods - the 4.0 pistons go in OK but you should put 4.6 gudgeon pins in the pistons as the 4.6 gudgeons while the same outside diameter have a thicker wall to take the higher loads.

Garry