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Farmall & IHC Tractors Discussion Forum
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Farmall M engine performance

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TYE W

11-24-2005 10:16:17




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Today I was trying to get the M to run correctly but little luck. The tractor has excessive back fire/pop out the exhaust at times. Adjusted carb, found to help but did not rid completely of back fire. Also recently performed tune-up (plugs,wires, cap and rotor and points). Checked timing and found it was off, set timing correctly. Timing helped to regain some power but didn't help back fire/popping 100%. Disassembled carb to check for dirt and debris- non found, also reassembled with fresh parts. Also observed, I can disable ignition on cylinders 3 and 4 with little to no change on engine idle. Disabling cylinders 1 and 2 nearly kill the engine-good spark at all four cylinders. Performed compression test and all cylinders were within 5 psi of each other. Approx. 95psi in each cylinder. Does anyone have any other ideas about what could be the problem? I suspect valve issues, does anyone argee? Thanks for any help.

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Farmall Daddy

11-25-2005 11:48:43




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 Re: Farmall M engine performance in reply to TYE W, 11-24-2005 10:16:17  
I would have to agree with Chad. I am having the same problem with my Farmall 560 not hitting on numbers 5 and 6 correctly. My two suspicions for your case would be, like said before, a worn bushing within the distributor. Another, which I had found on my 560 would be that the intake valves may be to tight and not shutting all the way, thus making a backfire through the intake system and then out the carb when the power stroke hits. If you are backfiring through the exhaust, your exhaust valve{s} would be too tight, thus not shutting all the way, and during the power stroke, being pushed through the exhaust valve and the rest of the exhaust system. Hope this helps, cuz I know the pain in the butt that little things like these can have on a guy!

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ChadS

11-26-2005 05:39:16




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 Re: Farmall M engine performance in reply to Farmall Daddy, 11-25-2005 11:48:43  
FD, 6 cyl,s like the lash a bit loose,, Get it warmed up, and run a compression check, when you find the low cyl, you found the valve(s) out of adjustment. I run my 263 at 32 hot, that is where it makes peak cyl pressure, but that lash setting could vary from engine to engine,,, I know, its not book specs for field use,, but it makes good power! Find a combine distributor, or a truck distributor, put a light set of advance springs in it and you will see a big difference. You may have a head gasket leaking inbetween 5 and 6,,,,, if it has no load on the engine, it can run and sound just fine, when the load is applied, the increased cyl pressure could float inbetween the 2 cyls and cause a pop, but its usually thru the intake when this happens,,, Check it in this order to find the miss,,,,, 1, warm it up, pull all the plugs out, run a compression test. Adjust valves if you find a low reading,,, 2, if the valves find a leak, and pressure increases, then check for vacuum leaks, Manifold gasket, carb gasket, you can spray a little carb cleaner around the manifold, if the engine speeds up, or smooths out, you have a leak, 3, If the cyl pressure is up, and no leaks are found, run it for a short period under a load, see if it still pops, if it does, shut it down, and look at the distributor cap, If you are running a high energy ign system, you may be carbon tracking inside the cap. New cap, and add a resistor to the coil.
If no carbon tracks are found, look at the plugs for color,, you want them a cocoa brown when its under a full 540 dyno pull,,,, Carb jetting and then maybe think about your cyl pressure, you may be under octane, or if your running race fuel, you may be over octane,,,
4, Ignition timing. Retard the timing, make it sound like its under a slight load, they like their timing, My 460 sounds like a car with a auto tranny, idiling in drive,,,,, not smooth or sewing machine smooth,,,,,
All of the above should find that pop,,,, and you should be able to cure it if no internal problems exist. Chad

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ChadS

11-25-2005 07:41:39




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 Re: Farmall M engine performance in reply to TYE W, 11-24-2005 10:16:17  
I have a Super M, and a 52 H that pops too. I think its in the mechanical advance in the distributor that causes the pop. My other Farmalls have the distributors rebuilt and they do not have this problem, but I have swapped distributors on the H and it did not pop any longer,,, What happens on the mechanical advance is that the springs and the weights get worn out, some stick, some kinda free float the rotor back and forth,,,,, Take the cap off and snap the rotor,, if it springs and comes back to full rest with good spring tension, its ok, but if it doesnt,, it may advance timing then stick in one spot, leaving the timing advanced and it will pop from timing being out from the advance not returning to the full rest postion. You can tell right off the bat if the advance is junk,, when you snap that rotor, and it feels sloppy and loose, you should have a closer look. Hope this helps,,, ChadS

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Yugrotcart

11-24-2005 14:39:51




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 Re: Farmall M engine performance in reply to TYE W, 11-24-2005 10:16:17  
Try adjusting the valves, both intake and exhaust should be set at 20 thou cold. Had a misfire in my W6, fairly new plugs. Replaced the plugs with new ones, solved the problem. Plugs that I took out looked fine, near new. Also are you using solid copper core pug wire?



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Wayne Swenson

11-24-2005 10:39:32




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 Re: Farmall M engine performance in reply to TYE W, 11-24-2005 10:16:17  
Are you sure the plug wires for 3 & 4 aren"t crossed? The distributor bushing may be worn causing erratic spark.
The manifold may have an internal leak on the 3-4 runner or the manifold gasket may be leaking. With the engine running, spray some carb cleaner on the manifold in the 3-4 area; if the engine smoothes out & speeds up you have found the air leak.
Have you run the engine at WOT (wide open throttle) & adjusted the high speed mixture screw in & out to get the highest r.p.m.? Then add ½-¾ turn out for power.
Going deeper, the valve springs may be weak or broken.
Work on the basics first; don"t go digging too deep until all the easy things have been checked (checked twice like Santa Clause"s list).
Good luck.

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TYE W

11-24-2005 11:08:57




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 Re: Farmall M engine performance in reply to Wayne Swenson, 11-24-2005 10:39:32  
Wayne, Forgot to mention that the tractor runs fairly decent under load/ driving uphill. Just thought of that info so thought I should share it. Thanks for the thoughts. ---Tye



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Jason Simmerman

11-24-2005 16:37:48




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 Re: Farmall M engine performance in reply to TYE W, 11-24-2005 11:08:57  
Also was the compression test done with the motor cold or hot? Makes a huge difference. Sounds like others have said eithor a crossed up wire, bad cap, or maybe even a burnt valve.



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