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M37 Timing?


maddmaxx1949

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Been working on the M37 today and trying to figure out no matter where this thing is timing wise all I am getting are back fires. Here's the shakedown:

 

1. Both oil pump and Distributor are the civilian type. 

2. TDC of Piston one on compression stroke is no where near marks on the balancer

      - When Piston 1 was at TDC I tried to blow air into the spark plug hole and no leaks.

3. Current electric is 24v regulated down to 12v for a standard 12v ignition coil.

4. Ran briefly a few months ago but only loped. Sounded like it was running on about half the cylinders and had to keep the gas pedal down to keep it going. eventually just died and could not get it going again

5. Major backfire through the carb and the muffler when I try and start. This is with distributor in normal position and flipped 180 degrees

 

Things I have done in no particular order:

 

1. Verified Timing at TDC using rear plug and tissue over the no. 1. spark plug hole. 

2. Took a timing light to it while it was "loping" and verified using timing light.

3. Replaced carb with carb from a smooth running 218 and pinched off the vaccuum line to the wipers to mitigate potential leak.

4. sprayed manifold while running and no change in RPM's 

5. At worst, all tappets are moving and valves which reside under the spark plugs are moving as well. ( verifying rest of valves tomorrow)

 Will also be doing a compression test tomorrow but felt strong from sticking my thumb over it (not sure how accurate that is but it was similar to my running flathead)

6. Fuel delivery is solid. pulling from a clean mason jar and good steady flow from the pump to carb.

 

 

I'm not sure what else to check for backfire to be honest. I've never had this much trouble with a flathead. Any chance It may have skipped a tooth or something? (not sure what those symptoms would be..) Open to any suggestions or ideas

 

 

 

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Remove the front valve cover and set it so #1 is TDC. Confirm the exhaust valve starts to open as you continue turning the engine over by hand. If I remember the spec correctly it should start to open around 12 degrees ADC. (Check the shop manual for the exact spec)   If it isn't correct the timing chain is installed incorrectly. If OK back up to TDC for #1, pull the distributor cap and it should be around 7:00. If it is off 180 degrees, pull the distributor and rotate to the correct location. If neither, oil pump is not correctly installed. Need to pull it and rotate so the distributor drive slot is correctly aligned. Then reinstall the distributor to the correct orientation. 

Lastly correct the location of the timing marks on the damper. Are you using the pointer on the front of the timing chain cover or some other location for reference?  Once you know it is all properly set up it will make tracking the issue (if it still remains) easier.  

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Trying to wrap my head around your situation.  You have located #1 TDC by checking compression at #1 (tissue paper) and top of piston stroke using #6 piston.  Marks on crankshaft pulley are "no where near" where they should be. If you had to estimate, how many degrees off are the timing marks on the pulley away from the pointer on the timing gear cover?   What did you verify with the timing light?  That the timing light works properly or that somehow now the timing marks on the pulley are correct.  As stated above by web master: next is to check proper valve timing wrt piston position.  With #1 piston at TDC on compression stroke both valves should be closed.  Pretty sure valves are visible through the spark plug hole. Are they both closed?  

My thinking is that the timing marks on the pulley really have nothing to do with the actual running of the engine.  If the crankshaft and camshaft are properly timed and the spark happens at the proper time with proper carburetion, the engine should run.  Sounds like it does or did although poorly from improper spark timing causing Backfire through carb and exhaust.  So, when you are at #1 TDC and lift the distributor cap, where is the rotor pointing?  It really doesn't matter as long as the spark plug wire on the cap above the end of the rotor goes to the number one spark plug.  Then verify from the #1 wire the other wires in a clockwise direction follow the firing order.  Please advise.  Merry Christmas and best regards.

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  • 6 months later...

Okay, so shelved the project for a while to work on other things. Cousin came over this weekend to pick up some things and look at it just for fun. We went through the timing procedure again, this time I had an extra long handcrank so I didn't have to bump the starter to turn it which helped immensely. Plus using a better sized rod for the #6 cyl. hole also helped.  Major adjustment on the distributor was way off from TDC and I couldn't get spark when I rotated the distributor during static timing. Adjusted major adjustment. Rotated distributor while on #1 TDC until points sparked. Tightened distributor down and hallelujah the truck is running strong. had to turn up the idle a bit so it didn't die. But, no more lope, no more rough running. Thanks all. Helps to get a second set of eyes when you are doing it and to take a step back for a bit. I swear I had timed it 15 times but I clearly missed a step and something wasn't clicking in my head.

 

Running off a gas can right now but going to get the tank flushed and hopefully have a functioning wood hauler here soon. Brakes optional of course.

 

 

Edit: I also did not see any timing marks on the front crank pulley, probably too much rust at this point but I will need to emery paper it at some point if I'm going to find them

Edited by maddmaxx1949
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