Re: Replace rings in '75 motor?
The 6hp is a pretty good motor and it's certainly worth tearing into to see what the problem is.
One thing I'd suggest is to pull the cylinder head, it's possible you may have a blown head gasket. With the head off, take a look at the cylinder bores and see if they're scored or otherwise damaged. If not, it's probably worth fixing.
But check the head and head gasket carefully, it's very common to see the head gasket on these crack & leak between cylinders, then you get very low compression readings on both cylinders.
A new gasket is quite a bit less than an engine overhaul or new motor so you really don't have anything to lose. You'd have to pull the head anyway as part of the teardown.
If you find it's a head gasket issue, you'll get better service out of the repair if you have the head milled/surfaced to ensure it's flat. A local automotive machine shop should be able to 'flatten' the head in short order for a nominal charge.
You can also do this yourself with a hunk of glass, flat on the workbench and surfacing the head on the glass after first laying down a suitable hunk of medium-grit sandpaper. After a few passes, the low spots will be clearly evident. Move the head about in a 'figure eight' pattern or similar until all the low spots are gone.
HTH & let us know what you find..........ed
