I posted this over in the Farmall area as well. Just wanted to get as much input as possible. I got a chance to compression test a Farmall 706 with a 263 engine tonight. Owners are putting in a Cummins diesel and sold the original engine to me. The engine starts great, idles great, no smoke, has good power in high 4th going down the road, and has very little blow-by. You can tell it has a little miss once the engine comes up to governed engine speed. While reaching wide open governed rpm in high 4th the motor sounds good and strong. Wide open at rated rpm going down the road you can tell there is a miss.
Compression test done with choke off, warm engine, throttle wide open, air cleaner hose off. First psi readings are just a warm engine. Second and third are with oil added to the cylinder.
.......No oil in cylinder.......Cylinder lubed with oil first series of cranks.......Lubed second series of cranks
Cylinder #1..........165..........250..........250
Cylinder #2..........150..........250..........250
Cylinder #3..........130..........250..........250
Cylinder #4..........160..........250..........250
Cylinder #5..........150..........250..........250
Cylinder #6..........90..........225..........150
As you can see cylinder #6 is weak. PSI comes up when oil is added to the cylinder. But still not to the PSI of the other cylinders. On the second test with oil added to the cylinders the PSI drops some. No more oil was added the second try - just another series of cranks.
What is cylinder #6 showing????????? Could the difference between no oil and oil added be showing a valve is going bad rather than the rings??? I was under the understanding that if oil was added it pretty much sealed up the rings and if you had lower compression readings that it would be the valves. I did not have time to check the valve lash plus I was at the sellers house and didn't want to open the engine up there. I will check the valve clearance before I take the head off. If and when I eventually take the head off and would happen to find good valves/seats can I just do the rings in cylinder #6??? Maybe the sleeve and piston should be done as well?? While I am there maybe I would do cylinder # 3 as well. Tractor will only do light chore type work. Thanks.
Compression test done with choke off, warm engine, throttle wide open, air cleaner hose off. First psi readings are just a warm engine. Second and third are with oil added to the cylinder.
.......No oil in cylinder.......Cylinder lubed with oil first series of cranks.......Lubed second series of cranks
Cylinder #1..........165..........250..........250
Cylinder #2..........150..........250..........250
Cylinder #3..........130..........250..........250
Cylinder #4..........160..........250..........250
Cylinder #5..........150..........250..........250
Cylinder #6..........90..........225..........150
As you can see cylinder #6 is weak. PSI comes up when oil is added to the cylinder. But still not to the PSI of the other cylinders. On the second test with oil added to the cylinders the PSI drops some. No more oil was added the second try - just another series of cranks.
What is cylinder #6 showing????????? Could the difference between no oil and oil added be showing a valve is going bad rather than the rings??? I was under the understanding that if oil was added it pretty much sealed up the rings and if you had lower compression readings that it would be the valves. I did not have time to check the valve lash plus I was at the sellers house and didn't want to open the engine up there. I will check the valve clearance before I take the head off. If and when I eventually take the head off and would happen to find good valves/seats can I just do the rings in cylinder #6??? Maybe the sleeve and piston should be done as well?? While I am there maybe I would do cylinder # 3 as well. Tractor will only do light chore type work. Thanks.