840 with Compression Issues

[Anonymous-0]

I just picked up a 1957 Ford 840, which runs really good, but when I checked the compression on the cylinders there was a large difference in the pressures. Here are my results Cylinder-#1: 148 psi, #2: 42 psi, #3: 58 PSI and #4: 152 psi. All of the cylinders held the compression for 5 minutes, no leak down. What could be the cause of the major deviation?

 

[showcrop]

I believe that it is indicating a bad head gasket. At least that's what it was on mine. you have a leak between 2 and 3. Otherwise very good compression, so your 840 is good otherwise, and a new head gasket is not a big deal. Just be sure you take the head to a machine shop to get it checked out and surfaced.

 

[Scoyt]

It does sound like a bad head gasket to me too. I have seen cars do the same thing, and it be a bad spot on the head gasket between the 2 cylinders.

 

[souNdguy]

I'll 3rd the idea of a bad head gasket!

soundguy

 

[Gene Hillman]

I'm not sure what you meant by "all cylinders held compression for five minutes". When an engine is stopped, the cylinders don't hold compression for any length of time. It equalizes to atmospheric pressure through ring end gaps in a short period of time. Normally, two adjacent cylinders with low compression is a bad head gasket unless you would happen to have to have a bad valve in each cylinder.

 

[Anonymous-0]

Thanks to all for the information.

 

[john_Bud]

You have a blown head gasket. If the readings on the compression tester were steady for 5 min, it means that the tester check valve was holding - not the cylinder.

Pop the head off, scrape it clean, have the valves ground, put on a new gasket and tractor off.

jb