Compression psi for Oliver 1655

Taw128

New User
Working on a Oliver 1655 diesel that suspect has a compression leak. When tested cylinders 1 through 6 tested at 290,300,300,300,300,250 psi. Does anyone know if 290-300 psi should be normal range for engine? Thanks
 
You are low! Take a cylinder leak down test and see where your leak is. When the head is off install seats so the valve protrusion can be set at the specified amount. Questions? J.
 
As John says, it's LOW. My 4-78 White forklift started hard when I first got it, all cylinders were 290-300 PSI range on the compression test. Pulled the head, all valves were flush to slightly below, which caused the low compression. Had ALL the seats replaced, and purposely got ALL the valves .085-.090 ABOVE the head surface. Now it starts much better cold, shows 350-360 PSI. I wouldn't be afraid of getting the valves even a bit farther out of the head as my pistons had valve pockets that were .140 inch deep, and with the head gasket in place valves are not even close to hitting. My opinion, but I'd rather have NO valve pockets at the piston top like Perkins uses. Then the head with flush valves would be fine.
 

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