slant six low compression how low is low?

Picked up an old Hobart G300 welder with a Chrysler engine. It's a 170 cu. in. slant six and I'm only getting 40 psi on each cylinder when I check the compression. I know it's only supposed to be an 8.5 to 1 comp ratio but doesn't 40 seem way low for even a 8.5/1 motor? I don't have any experience with these sixes so guess I could use some advice.

Thanks

it's almost deceased. Only a /6 could still run with it that low. You might adj the valves, .010" intake/.020" ex and I like to loosen the plugs several turns then tighten them up & reinstall the plug wires & start it & rev it to blow the loosened carbon chips out which can lodge under a valve & give a false low reading (but not low like you have) & only takes an extra minute or 2 when doing a compression test.

Lol, yea that's what I figured. I have no idea how long it's been since the thing ran, bought it at auction a few years back and just now getting around to messing with it. Hopefully they just parked her because the engine was weak rather than a problem with the welder head. I would probably spend a few bucks and overhaul the six but probably tough finding parts for the generator side and $$$ too.

You might pick up a /6 for cheap and or see if the welder head is OK first

I've hot a cheap 225

spray alittle oil in the cylinders,see if it comes up. a sitting- dry engine will have low #'s. a little oil might help.rings could even be stuck in place.oil might free them up also. at 40 lbs I wouldn't expect it too run.

You are going to need at least 100 psi cranking compression to get it to run.

Pour some turpentine down the plug holes and let it sit overnight. As said before, check the valve adjustment too.

One thing you will have to watch swapping a 225 in will be clearance for the top of the motor, and exhaust routing. The 225 is taller than a 170 by a couple inches. Also, the crank flywheel register diameter changed in 1968 so your coupler may not fit.

FYI, 8.5 is probably optomistic. True cr is usually closer to 7.5:1.

Might want to check the timing chain.