ORIGINAL: adamw2k2
Hi just joined the forum, looks really awesome!!
I currently have a GX31 and am looking to increase the compression ratio from the standard figure of 8:1 to around 10:1
I have heard that with a GX35 engine, a piston from a GX31 can be used to increase the CR, but can the connecting rod of a GX35 be used in a GX31 to have the same effect of increasing CR?
now thats it lunch time and I have time to explain.
The connecting rod in the GX35 is longer than the connecting rod in the GX31 by .197" The piston will collide with the head. There is not enough material to machine the top of piston, long before you lower it enough the ring grooves will be gone and there will be a large hole in the piston. No room to machine combustion chamber either.
Not to mention splitting the crankshaft to remove the rod and for reassembly requires special tools.
Plus you cannot buy connecting rods, they only come on crankshaft assemblies.
The only way to increase compression in the GX31 is to offset bore the wrist pin hole to a larger size and bush back down to wrist pin size.
(tig welding the top is not recommmend)