M211 - Too Slow

[delos]

My M211, well actually a M220 shop truck with a water tank, is maxing out at 30, downhill. The engine runs good but after sitting for more than a few days it requires oil squirted in the cylinder to build up compression or it does not have enough to get running. After it starts one day, it starts up the next day and the next... So maybe a compression issue? I have been thinking about disconnecting the front driveline and the front rear or rear rear to lessen all the mechanical drag. Any ideas on how to get it going faster? Would adjusting ignition timing significantly improve performance? Any suggestions would be appreciated

 

[Oldfart]

My experience with oiling a cylinder to improve compression sufficient to start causes me to suspect valve seat leakage as a first. If the engine is having that much trouble, it would be best to run a compression test to see it was all cylinders or just one or two.

I have recovered engine compression and performance by squirting large amounts of upper cylinder cleaner into the spark plug hole and allowing things to soak for a couple of days. Using the same technique I have freed broken rings and removed gunk from valve seats that allowed what little compression I did have to go away. I view this method as last chance before the rebuild. The older upper cylinder cleaner chemistry worked better and it consisted mostly of Butyl Cellusolve, but hard to find that nowadays.

Tuning changes can make a difference, but it sounds more like you are suffering from a loss of Horse Power due to a worn engine.

 

[delos]

Thank you for your suggestions. I will do a compression test after i run it across town and let it cool - then post my results. Any ideas what a rebuild costs for one of these engines? I can do all the work except the machining.

 

[Oldfart]

delos,
Last engine I had rebuilt cost me $1250. It was a Chevy V8 and I hired it all done. We found it was almost the same cost to hire our engine shop to do it all as it was to pay for the machine work and rebuild kit. (about another $150 for the labor and that way I got 12 months and 12K mile guarantee.) Our engine shop was about the same cost no matter the engine (diesels more of course.) There were lots of GMC 302 engines out there when these trucks were put on the road. You should be able to find a used engine for around $800 if you have the luxury of time to look. If you don't care about original, the bell housing will accept OLDS, Pontiac or Cadillac blocks prior to the one engine fits all GM time frame.

Check out "Gunfreak", he has his truck for sale, but he has shared his restoration work on Steel Soldiers and you might find more information there. His has an Olds engine.

Idaho Motor Pool is not to far from you and I know they have dealt with these series of trucks. They might be a source of parts and knowledge.

 

[clinto]

I would run a compression test as well. Get a baseline so you know what you are working with.

 

[nattieleather]

If you want to keep it original then yes do a compression test and see what is going on and then change accodingly. If your not concerned about original then you have options from V8 gas motors to diesels. Keep us posted on what you find and what you want to do. Good luck!

 

[emr]

Its a slow truck and always will be, That truck any faster is dangerous, now if u have some motor issues that can be fixed for it to run like its supposed to it will still be slow, and was meant to be, A different hobby Is what i see for faster trucks, really no disrespect intended, just the facts. Good Luck !!!

 

[pa.rich]

Mine will go about 50 mph. Are you sure its not in low range? Not trying to insult you. I agree about the compression check.

 

[natem]

I would also do a quick vacuum test.

Nate

 

[hippiedude]

Check all vacum lines first , then do a compression check cold first then do it hot .....That truck should do 50 to 55 mph....By the way that is a good looking truck ...... PS you sure that tank is empty .... ...... Good luck ................. Tim

 

[Gunfreak25]

Actually Old Fart, I closed the ad on my truck earlier today. I was frustrated with the truck so I put it up for sale. After a cool off period I want to keep it again. Best thing a man can do is walk away when the frustration sets in.

 

[Stan Leschert]

Our M135 will do 55-58 MPH on the flat. 45-50 is a good cruising speed, and I know that it has exceeded 62! Not me, Leo was late for work! Hills will be slow, but I have yet to meet a hill that it won't crawl up!

 

[Oldfart]

Actually Old Fart, I closed the ad on my truck earlier today. I was frustrated with the truck so I put it up for sale. After a cool off period I want to keep it again. Best thing a man can do is walk away when the frustration sets in.

Our M220 keeps growing on me. I do wish some things were more available (like airpacks) and we were farther along with our van body restoration, but I keep telling myself we are lucky to have started off with something as complete as it was. Glad you decided to hang in there a while longer.

 

[jollyroger]

Oldfarts 220 runs 55 all day long with the empty M-105 behind it, on the flat. It sniffs a hill and it slows down. The truck runs really good. I have been impressed. Everyone we talked to said they are slow as molasses in January. But honestly it out performs all of the stock M-37's I've run. And the brakes will shut her down.

I just drive it like all my other MV's. Tons of room left to stop. I'm not in a hurry to accelerate. Put myself in a clear traffic area, i.e. no cars around me. Anticipate traffic and let people merge in front so they don't get upset about being stuck behind the big truck. Common sense stuff the Oldfart taught me.

I would check for the simple things first. Is it stuck in low? Great question. Vaccum line check. Etc.

But with your explanation of not starting after it's cold or sitting for a period of time and you have to wet the cylinders to get it to start I would suspect low compression. I have had a lot of old GM inline 6's that have worn out and needed rebuilt or replaced. Most due to loss of compression.

Low compression. Hole in the top of the piston (detonation). Not likely. Valve(s) worn or damaged. Possible but usually accompanied by a dead hole or missfire. ALL of the valves don't usually go bad at the same time. Stuck or worn rings/worn cylinders. Most likely.

Bad rings/worn cylinders. Symptoms. Hard starting cold to impossible to start cold. Improvement in starting wetting cylinders. Excessive blow by into the crankcase. Low compression check numbers. Spark Plug fouling. Buring oil in the exhaust. Oil consumption. Raw oil in the exhaust.

Honestly a leakdown test is more accurate than a compression test but for these purposes a compression test will narrow down the problem Cylinders and or if the engine is just plain worn out. And a compression test is easier to perform and the test tools are cheap to get.

Good luck and keep us in the loop.

 

[delos]

Working on the rig today...Will post an update tonight

 

[rchalmers3]

Hey guys, I'm not a gas powered MV expert, but I'd like to toss in another idea about old gasser trucks.

When the ignition points (or distributor bushings!) wear out, the point gap closes and the dwell can shift to the point where the spark arriving at the plugs is weak and late. It can make trucks very hard to start!

My recommended method of diagnostics would be to warm up the engine and measure dwell, base timing and advance timing. Correct anything there then measure the engine vacuum, which will give you an indication of the general health of the engine mechanical condition.

I would only bother to measure compression if there is a discrepancy in the vacuum readings, such as fluctuating readings or constant low readings.
My .02c

Rick

 

[pwrwagonfire]

I like the paint job, what was its use in a former life?

 

[flighht2k5]

How is dwell checked?

 

[rchalmers3]

How is dwell checked?

Good question.

Back in the day, there were analog instruments made expressively for measuring dwell. You simply connected the tool, set the scale for the number of cylinders (or selected the correct multi-scale on the dial face) and ran the motor. You could (on some vehicles) adjust the points while the engine was running to obtain the proper dwell. Most cars required an "adjust and test" method to obtain proper settings.

Today is a different day. My Fluke automotive multimeter has a "Duty Cycle" setting that gives exact measurement of points closed time (dwell). However for any motor of more than two cylinders, you must perform a calculation to derive the dwell from the duty cycle. This table is printed at the back of the Fluke manual and is an obvious vestige of the earlier years of automotive diagnostics! It makes me feel like a dinosaur to recall that I once used a dwell meter extensively.

Rick

 

[delos]

This particular rig is stenciled US NAVY on the inside of the drivers door, the inside is original OD Green. The County had it for 20 or so years, well as long as anybody could remember, they just used it for trash fires and keeping the dust down around the waste transfer station. Also, the serial number/vin is 666 Ha ha ha

I checked the centrifugal advance mechanism on the distributor, and it works properly as far a i can tell. I sprayed some pb blaster in there to keep it that way. the pb blaster loosened up the screw that holds the points contacts in place. pretty easy to figure that one out, I put a nut on the backside and it is ok now.

Ok so I did a good compression test today. Took all the plugs out, throttle open and about 10 seconds of cranking on each hole. The results are from 1 to 6.=====90 60 58 66 2 105===== The one that flunked is cylinder number 5, which also has a wet plug(oil) all the other plugs looked a little black, but healthy. I put some marvel mystery oil in each cylinder and it is soaking now.

It looks like we have a dead hole. I bought a gasket kit on ebay, so It looks like i'm pulling the head at some point. Probably should take a close look at the valves? What kind of bad things can happen running the truck with a dead hole?

Thanks for all the help folks!