It's getting new rings with a dingle ball hone this time instead of the flat stone hone I used last time (which probably did more harm than good). New 0.001" oversized bearings to tighten up the bottom end. As for knurling, I didn't measure out the bore versus piston diameter, but I'm not sure how much run time this engine got after the over bore, but there is no ridge at the top of the cylinder, but on the same token, if there was ever a cross hatched hone done, it was gone.
I'm going to be measuring how far the pistons are in the hole. I measured it when I pulled it apart a few years ago but cannot remember the number now. All the pistons are 0.030" over, so I guess whom ever rebuilt it last could only come up with four pistons from one supplier and got the other two to round out the engine. When I first disassembled the engine after getting it I was expecting just the two cylinders to be overbored, lol.
I still am having a pro do my turbo head, this is just going to be me working it over.
I'm going to smooth out the ports and open up around the backside of the valves and smooth out the valve guide bosses. Along with reshaping the chamber around the intake valve. Also remember, for the short turn radius that these valves are canted, not straight up and down. I'll cc all the chambers and match them up best I can then run the compression calc's with all the other pertinent measurements and then shave the head accordingly to bring the compression up to 9.0-9.5:1 if I can, but it may be tough to even get that high with these pistons. I'm thinking about having the intake/exhaust surface shaved some, but I don't think it can be shaved enough to true up the 1/16th to 1/8th inch gap on the intake. When I call the machine shop on Monday I'm going to see how much and if he can install bronze inserts on the valve guides to tighten up the seal around the valve stems. Or speaking of knurling, maybe I'll inquire about doing that to the valve guides.
I'm going to cut and grind the divider out of the intake plenum as well to promote intake flow. Its also getting more valve spring pressure so I can wind up the engine as high as I want to find peak HP. There is minimal harm in over springing an engine as long as it doesn't eat the cam.
Rebuilding an OHC Pontiac 250 with EFI and a Turbo