Command 25 hp bent pushrods on one cylinder
Ok, so I have this kohler Command 25hp engine that's 20 years old. I just finished putting a shortblock on this engine, reusing the heads and valve train. Upon assembly and re-insertion into the tractor, it ran rough. Upon checking, I found 0 compression on the #1 head. Performed cylinder leakage test on it and found nothing significant. Pulled the lifters and bled them just to be sure. Still nothing. Just on a whim, I stuck a washer under the intake rocker arm stud to give me more clearance, and had compression. I ended up having the stick 2 washers under the rocker arm bolt to get it to work once it was all torqued. I let the engine run about half idle for about 45 minutes then parked the tractor for the night. When I got home tonight, I fired up the tractor and started mowing. About 6 feet into mowing, I heard a pop and then the engine just bogged down. I bent both push rods on the #1 cylinder and the exhaust valve keepers had popped off.
I've checked for bent valves, both valves move freely by hand when I compress the springs. I also checked the valve guides and they both seem to be at the right height.
I've had issues with the heads on this thing for years. Every couple of years I've had a head gasket blow on it. I've resurfaced the head each time, checked and re-cut valve seats when necessary. I've had threads all over these heads strip when they weren't even tightened up to torque. The rocker arm bolts stripped out in the heads and I drilled them out and installed a steel insert for them to screw into. This is the only thing that physically I can think of that is different.
I'm thinking new heads are the way to go, and if I do so I'm replacing both heads and the complete valve train. The # 2 cylinder seems fine at this point, so there's something specific to this side.
I know resurfacing the heads and cutting the valve seats can throw the specs out if i do it often enough. I'm tearing my hair out over this.
HELP!!