Crankshaft End Play on Rebuild

[Bud Man]

Had my 29 A motor completely rebuilt (stock specs except for inserts a 5.5 head) and I reinstalled it last month. Runs and drives well, with clutch and trans both smooth and positive. Discovered today that the crank end play is in the .035 - .040 range, way out of spec. Was fine tuning the clutch free play a bit and noticed an audible clack when I would depress the pedal with the engine off. Emailed the engine builder, a well known shop that apparently does several A engines each year, and he emailed back that it (quote) “sounds like something must be pushing on the crank from the clutch side too much”. He also indicated that all A engines leave his shop with cranks set at .005/.006”. I am far from an expert on Model A’ but I have rebuilt engines in the past, and am at a loss as to how this crank spec would have changed so dramatically after less than 50 miles on the engine. Break in has been gentle and up to now, the truck performs well, but don’t know what to do at this point. Hoping the folks on this forum can lend some expertise and advice.

[darrylkmc]

Hi Bud Man,

I am sorry to hear about your newly rebuilt engine, but your thrust change with your engine is completely unacceptable.

There is babbitt from your rear main bearing thrust surface in your pan.

I would guess that the thrust area of the Crankshaft is rough and has gouged into the thrust surface of the babbitt.

This needs to be returned to the engine rebuilder, it should Not be run again until it is determined what is cutting your thrust babbitt.

Darryl in Fairbanks

[redmodelt]

except for inserts

[darrylkmc]

Unacceptable either way, the Babbitt or Bronze is being gouged out and is going to be in the pan.

[Kohnke Rebabbitting]

If he sets up at .005, or .006., any thing after .006 is wore out, and that is using a crank, with old bearings.

It doesn't make any difference if it is insert thrust, or babbitt thrust.

New bearing thrust on either should not be under .003, and not over .004.

Herm.

[Bud Man]

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I appreciate all the help. Planning to drop the pan today and will take a look. Very, very disappointing, to be sure. Thank you again! Bud

[tinkirk]

Originally Posted by Bud Man

I appreciate all the help. Planning to drop the pan today and will take a look. Very, very disappointing, to be sure. Thank you again! Bud

you might want to bring the car to the re-builder so he can see what you have going on and let him drop the pan so he has no excuses!
i know if it was a motor that i put together, i would not want someone else to take it apart

Terry

[Bud Man]

Removed pan yesterday, and as expected, lots of fine bearing material in the very bottom. Removed rear main, and also as expected, the flywheel side bearing was worn, miking out at .216" (the other rear bearing was at .251", showing next to no wear). The worn bearing exhibited no serious gouging on the crank flange side and appears to be a fine ridge of displaced metal - "squish" - along the entire outer edge. So, it looks as though there has indeed been some serious pressure against the crank. I am at a loss, as prior to joining the transmission to the flywheel housing, I measured the distance between the input shaft nose and pilot bearing, and it checked out fine. The two assemblies mated easily. Clutch has performed well since the rebuild and the T/O bearing is not touching the clutch fingers when disengaged. Has anyone on the forum had a similar issue and if so, any suggestions on where I should be looking at this point?

[tinkirk]

Originally Posted by Bud Man

Removed pan yesterday, and as expected, lots of fine bearing material in the very bottom. Removed rear main, and also as expected, the flywheel side bearing was worn, miking out at .216" (the other rear bearing was at .251", showing next to no wear). The worn bearing exhibited no serious gouging on the crank flange side and appears to be a fine ridge of displaced metal - "squish" - along the entire outer edge. So, it looks as though there has indeed been some serious pressure against the crank. I am at a loss, as prior to joining the transmission to the flywheel housing, I measured the distance between the input shaft nose and pilot bearing, and it checked out fine. The two assemblies mated easily. Clutch has performed well since the rebuild and the T/O bearing is not touching the clutch fingers when disengaged. Has anyone on the forum had a similar issue and if so, any suggestions on where I should be looking at this point?

kind of hard to tell without actually being able to see it, but my thought go to, Was the rear thrust bearing pinned into the block or just floating around in there ???

Tinkirk/Terry

[Kurt in NJ]

How smooth is the thrust surface on the crankshaft, one of my practice crankshafts I didn't dress the grinding wheel correctly and it made a rough surface almost like a file on the thrust

Is the rear thrust bearing full circle or just 1/2

[Bud Man]

Terry,

Engine was converted to inserts, so the 1/2 bearings just roll up into the grooves machined into the block, and both are held in place by the rear main cap.

Kurt,

My finger tells me its very smooth, and the worn down side of the bearing itself appears relatively smooth as well, with some very lite scoring, but nothing approaching deep grooves.

Appreciate the replies!

Bud

[tinkirk]

THE BACK OF THE REAR MAIN BEARING BLOCK AND CAP IS TO BE COUNTER BORED .125 DEEP AND 2.250 DIAMETER
THE REAR THRUST WASHERS ARE HELD IN PLACE BY COUNTER BORE AND CRANKSHAFT. THE BLOCK THRUST WASHER IS TO BE DOWELED TO BLOCK TO PREVENT ROTATING. THRUST WASHERS ARE NOT TO BE ATTACHED OR SECURED AS THIS CAN CAUSE END LOADING AND ABNORMAL WEAR.

THE FRONT OF THE REAR MAIN BEARING BLOCK ONLY IS COUNTER BORED .125 DEEP AND 2.250 DIAMETER
THE FRONT THRUST WASHER IS HELD IN PLACE BY COUNTER BORE AND CRANKSHAFT. THE CAP NOT COUNTER BORED WILL PREVENT THE THRUST WASHER FROM ROTATING. AGAIN THE THRUST WASHER IS NOT SECURED TO


this is how both of mine are set up

Terry