3 Cylinder Rebuilt = Low Compression

Steven B

1) About the bext compression you'll see is 350-400 max. That's at a decent cranking speed. When Ford first came out with the 450-500 figure, that was with the engine running at idle, which they later changed to a cranking test. Keep in mind that if your battery is weak and the cranking speed is sluggish, your compression will be lower. Also, you do have all the injectors out when you do this, right?

2) Piston deck height is VERY important. Not only were there different types of pistons, there were also different thicknesses of head gaskets. Using a thick gasket where a thin one should be will definitely cause hard starting when cold. It's amazing the difference just .020" can make.

3) I seriously doubt you can mix up the pistons (gas to diesel) and still be able to start the thing. According to the picture I have, the gas pistons have cutouts on the tops for valve reliefs.

#2) I really like your idea about the "Head" gasket, that one did not come to me at the time. I've contacted my engine rebuilder to verify which H/G was installed and I will cross check it with my local Ag dealer.

#3) I also thought that a mix-up in pistons was unlikely but they also had a 3 cylinder gas in the shop at the same time.

Since my first posting I've had the tractor on a small 6' chopper for 3-4 hrs, and it seems to have power. I've returned the tractor to its owner with instructions to work it well and I will re-check everything in a month or so.
I will let you know how things turn out.

Jim Maxwell

Reading between the lines I assume the valves and seats were cut, within specs and lapped. All else on target i would wait and see how it started when cold.

Jim Maxwell

Jim Maxwell

Jim Maxwell