Rod End Shake - Too much?

Bottom End (crankcases and crankshaft)
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Rod End Shake - Too much?


Post by Ripley/Fla »

Upon disassembly of my top end I found that the front cylinder rod has a lot of side shake. I can cock it. The rear or wider one has almost none. What is the correct way to determine rebuild time?

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Post by FlatHeadSix »


Read the shop manual, a small amount of side play is both acceptable and expected. The up-down play is the critical test. Pull the rod straight up and push it straight down, if you can detect any play that way its time for a bottom end rebuild.


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Post by Cotten »

Once upon a time,
I was working out of a street shop with a crew of serious motormen.
Every time a top end came off, we would line up, stick our tongues between our teeth and "feel' the rods for a guess as to their condition before they came apart.

The best method of inspection (without disassembly) seemed to be to wash out the crank with solvent, and then grasp each rod with one hand to pull upward, while smacking the rod top with the other fist, at many different degrees of rotation.
Extreme clearance would sometimes produce a knocking sound.

This still failed to display spalled races.

A freshly rebuilt male (front) rod will have ~.030" sideplay at the top; Worn but serviceable rods could display up to .090", but oil-starved cranks could show anything, even less than .010"!

An assembled crank might as well be at the bottom of a bucket of paint: You cannot divine its condition by touch and feel.

Unless you personally know the history and service of a motor, it's broke.


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Post by fourthgear »

Well said ! Disassemble & inspect and repair as needed.

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