Posted by Jack Smith on May 14, 1998 at 03:22:15:
In Reply to: 251/265 Compression Ratios posted by Dave Hamann on May 14, 1998 at 00:20:33:
I'll try this and see if my ISP cuts it off short like my most recent messages. The heads will interchange as long as all water inlets and outlets are the same. Check the ports carefully and make sure the new head will get proper cooling. Some of the industrials and marines had a water inlet at the rear of the block in line with the spray tube. If your block has this triangular inlet, you're stuck with the original head, as the rigid copper pump tube will not have anywhere to hook up to. If this is not a problem, also take a close look at the crank snout, to make sure you don't have an engine that was made to drive off the snout end. These had a flywheel housing that just enclosed the flywheel edges, and no clutch. The clutch box drove off the crank nose. Also make real sure you have a standard rotation engine, as they were made in both rotations! The gears, cam, and some other parts are opposite. The changed head should raise your compression ratio, but these engines ping readily at 8:1, so don't go too far. That doesn't leave room to cut the head much more, when the head gasket blows. Notice I said "when", not if. As long as you have the thing torn down,check the block real close between #3 & #4 cylinders, and if it shows any sign of burning, the previous gasket had a leak there. You need to repair any erosion there or it'll blow again prematurely. Try to get a copper head gasket, and use a bit of grease on it when you seat it. You should have the sodium cooled exhaust valves in your industrial, and the stems are almost twice the diameter as the solid valves, so expect a puff of oil smoke from the guides when you decelerate and start cold. The big guides have a bit of trouble with oil control, but it's normal. Can't think of any reason this shouldn't work! Good luck!
Jack