Cylinder Block

Theory:- Fact is, the good old agricultural GX160 is flawed by a number of things, particularly bore leakage due to poor quality materials and finishing in the bore. All other things being equal, a good bore will generally give you a good engine, a poor one a weak engine.  Unfortunately, there are more poor and average ones than good ones ! Hence the Torque honing and the parts matching which currently has a significant effect.  You want the cylinder to be perfectly round when the engine is bolted together and at operating temperature, not when at ambient and bare.

Hone the cylinder with a torque plate and the side cover, both torqued to spec, 218 in/lb. Assemble the crank/piston/rod and install in the block.

# bore in line with crankshaft

# bore that stays round when head is tightened down

# Fit new piston rings and gap the ends

Put all short blocks back together and check for deck clearance. Now take the one with the smallest deck clearance and take it back apart. Measure the compression height of the piston that was in that engine. Start measuring all the other pistons until you find one that will bring you to Zero deck or as close without going over.

Crank Rod

While you have everything apart, plastic gauge the rod/crank clearance. You want it between .003" to .0035". Lubricate the lifters with a very light weight oil, i.e. sewing machine oil, WD40. Insert the lifters and make sure they move smoothly and require almost no pressure to move them.

# longest stroke available,

Fly Wheel

Weigh each flywheel. Out of all the engines you should find one that weighs about 2390 gms.

# lots of ignition timing advance

# light flywheel/fan

Cams

# lots of inlet valve timing and overlap

Degree out every cam and find the one that gives you the greatest area under the curve. Use that cam.

Cylinder Head

# brand new head bolts to get them nice and tight

Head that has minimum chamber volume and still meets the thickness spec.