Compression (large difference)

[frippe123]

I have had a rough couple of weeks with health issues in my family so today I went out tinkering trying to get my mind on something else. I tried to get one of the Power Wagon chassis I have standing started but it wouldn't start. First the starting motor wouldn't crank over. I managed to fix that by taking the "push"-button apart and clean the contacts. When the starter was once again mounted it would crank the engine over just fine. Spark was weak but I already knew that because of how worn all the ignition parts were and new parts are already on the way.

I managed to get hold of a cheap compression tester. First I thought the compression tester was nonfunctional as I tested it on cylinder one and six and they both game me zero compression. I swore I would newer buy a cheap tool anymore as I always do. However the other PW chassis I have do start so I tried the tester on one of those cylinders and got really good result.

Back to the original chassis knowing the tester was ok I managed to get good compression in some cylinders and bad or none in others. This is the result on each cylinder:

1: 0 psi
2: 80 psi
3: 65 psi
4: 0 psi
5: 88 psi
6: 0 psi

What would you say would be the major problem? Stuck valves, broken camshaft or something else?

[Desoto61]

For either option the answer seems to be the same, you need to pull the valve cover plate off and see what's happening, that's the simplest place to start I'd think.

[Cheyenne Dave]

There is nothing simple here, not with 88 psi as the best reading. Almost seems to have jumped time, but I am guessing that would be only a starting point.

Your were gonna do a complete rebuild anyway, right?

cd

[Charles Talbert]

I have had a rough couple of weeks with health issues in my family so today I went out tinkering trying to get my mind on something else. I tried to get one of the Power Wagon chassis I have standing started but it wouldn't start. First the starting motor wouldn't crank over. I managed to fix that by taking the "push"-button apart and clean the contacts. When the starter was once again mounted it would crank the engine over just fine. Spark was weak but I already knew that because of how worn all the ignition parts were and new parts are already on the way.

I managed to get hold of a cheap compression tester. First I thought the compression tester was nonfunctional as I tested it on cylinder one and six and they both game me zero compression. I swore I would newer buy a cheap tool anymore as I always do. However the other PW chassis I have do start so I tried the tester on one of those cylinders and got really good result.

Back to the original chassis knowing the tester was ok I managed to get good compression in some cylinders and bad or none in others. This is the result on each cylinder:

1: 0 psi
2: 80 psi
3: 65 psi
4: 0 psi
5: 88 psi
6: 0 psi

What would you say would be the major problem? Stuck valves, broken camshaft or something else?

0 is bad, 88 is really just as bad. Readings of around 105 PSI or higher would be called good, or decent. 100 is borderline, below that will be causing some issues. The ones yielding 0 is most likely due to stuck valves. Put a couple of pumps of oil in the plug holes of 2, 3, and 5. Retest immediately after pumping in oil. If the reading jumps up significantly, ring and or cylinder wall issues is the problem there. More likely than not, it's a waste of time. I don't expect anything short of a major overhaul will help the problems at hand.

[frippe123]

Thank you Charles, Dave and Desoto61,

Plan? I actually does not have clear path at the moment. As I'm both purist and not purist my goal is (as with my cars) to end up with two running trucks, One original truck with cab and bed (the purist) that does not have to be in pristine condition at all, just original. And a second truck that could be little modified and does not have to be period correct. None of the chassis I own have cabs on them. The white 40s-something which is the one that does not want to start is missing papers so I really can't do anything with it except use it for parts. The green -56 that is starting has papers and is like the white 40s heavily Bubbafied. It had excellent sheet metal on fenders and running boards until someone got the great idea to put enormous tires and therefore cut them up.

As of several years back I am still searching for Power Wagons to acquire but have yet found one with a decent cab worth importing to Sweden. The ideal solution would be to find a complete pre-50s truck and a 50s cab with doors for my -56 frame. I have found a pre-50s truck without a good cab in the states and a civilian 1/2 civilian cab in Holland. The price for the cab in Holland is steep, would need some alterations to fit and the firewall looks different. I have not yet decided if that would make the truck pure enough for my liking. Also the customs have started to question whether a truck in need of restoration can be a collectors item. If I decide to use the -56 as a base for the non pure truck cab year doesn't matter.

So the plan is that there is no plan. But as I patiently wait for anything to show up I need to have a few projects that are not directly related to the "husband to do list" and overhauling an engine might perhaps be that. I have never done that before but I am always fun to learn new things. The most I have changed to an engine internal is a camshaft on an Opel Kadett.

Anyways enough rambling. Back to the engine in question. I removed the valve cover which took quite some elbow grease as there was some black goo used as thread locks on the valve cove bolts. In hind sight I should have removed the front fender as that would have made it much easier. The engine did not look pretty. The 1 and 6 valves were permanently stuck and the 4 moved slowly. I don't remember which ones were were intake and exhaust. Everything was sooty and there was quite a buildup on a few of the cylinders. One valve was whitish. I sprayed penetrating oil down the neck of the stuck valves to see if that will release them.

Is there any good engine literature available that relates to overhauling this specific engine?

[gmharris]

Much of the information available online is for Dodge military trucks. Some manuals are available on CD's from various suppliers. The military M37 is similar to the Dodge FFPW. Manuals for the civilian FFPW are often available on Ebay.

Here's and interesting site. I haven't had a chance to do anything with it since the internet connection I have here is too slow. Looks good though.

http://www.imfmotorpool.com/M37_Manuals.html

As for your trucks, I would focus on just one truck. Leave the other for parts or sell it.

[frippe123]

Thanks GM-harris for the link and tips. Will definately try it out. I think I read on this forum or on in the PWA magazine that the military manuals are written for an audience with a little less experience in automotive work which would suit me well. I have a paper repair manual for 1949 trucks and a 1956 manual on cd so I think I am set there.

My long term intention with the trucks now would be trying to find a cab and merge the two trucks into one. I would probably take the frame from the -40s truck or atleast the rear cross members and use the driveline for the -56.

But I might want to fix the engine anyway just for fun and learning.