super m knock

jdetig1 · Sep 27, 2009

i rebuilt my super m and i hooked it on a 3 bottom plow and now at an idle there is a slight knock coming from the front of the engine maybe the crank. i put a different engine in it but used the main bearing caps from my old engine could this be the problem? if i take the belt off the power steering pump the noise stops but i dont think its the pump, could it be the pullys on the front of the crank? also if i speed the rpms up it stops you cant hear it but once in a while you can feel it.

rustred · Sep 27, 2009

i guess that would be a problem,unless you line bored it with those caps!everything is matched and should be #erd. you cant take one cap and put it in a diff. spot. if you dont have caps for your block its useless,basically junk.luckey the crank even turns, most time it will just jam up.bet you didnt plastigage it either. that would have given an indication of trouble. thats why when someone says its just o/h i get really leary of backyard mechanics.guess you better get that engine out and do it right.

David G · Sep 27, 2009

Caps are line bored for that engine and not interchangeable. It would be prudent to stop using it before your break something major.

scott mcintosh · Sep 27, 2009

Without line boring block,you just went to alot of work for nothing.Had a fella who did same thing with 300 Ford 6 cylinder motor he had me check out that someone worked on prior to that.High priced boat anchor.Scott

Bob M · Sep 28, 2009

If the knock disappears when the steering pump belt is removed look for loose crankshaft pulley(s). (You certain the big 2-1/2" nut that holds the pulley is tight?)

Another possiblity is the camshaft gear hub has cracked. This is a common failure on live pump-equipped Super M tractors. Test by lifting an implement with hydraulics with the engine idling. If the knock changes or disappears when the pump's loaded it means the cam gear is going away.

My money's on a loose front pulley however!

Janicholson · Sep 28, 2009

AS noted below bearing caps are not interchangable. you probably have more than .005" clearance on #1 main. When pulling up on it with the belt, it opens the clearance. when it fires, it slaps the clearance into the cap. (my guess)
To check it, make sure the pulley is tight, then use a dial indicator on the pulley flange, positioned so it is vertical. Use a pry bar to push down on the pully flange. set the dial to zero, then push up on the flange and read the indicator. At that distance from the bearing it should not be more than .005". (this probably translates to about .003 at the bearing) if it is more, do not run it till it is fixed. As stated, line boring is necessary (with the cap fit to allow metal to be removed (shaved cap mating surfaces) Best of luck, JimN

super m knock

jdetig1

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rustred

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David G

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scott mcintosh

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Bob M

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Janicholson

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