Originally posted by rcpilot
I just bought a used ns12s3, bad idea. There was supposed to be a gallon on the engine but its completly out of compression and there is a very large amount of play between the crankshaft and connecting rod. Does anyone know appropriate running dimensions for the connecting rod end and crankshaft end where they meet? Should I replace the connecting rod or just the crankshaft? Would a rod from an mr12 fit? Also would it be a good idea to get the p/s squeezed or better replaced? And one last question, what size head shim does this engine normally come with stock, this guy had 7mm clearance, I am used to running 3mm.
Any help greatly appreciated.
Standard crank pin should be 4.27mm. Crank should be changed when it gets to 4.23mm. Now if your crank is in between that range, most probably is conrod bushing out of measure, conrod should be changed if play is .05mm with crank, provided crank is between above measures.
I wouldn't do p/s squeeze on such a high revving engine, better change p/s.
As per head shim, standard shim for Nova based engines is 0.3mm (silver aluminum shim) which is good for running engine with up to 30% nitro, but if you are running 20% nitro you would do better with a 0.17mm shim. If you are running 25% nitro you should have a 0.21mm shim.
AFM