'48 C60 engine rebuild

[Stoffregen Motorsports]

I made good progress today, in my view, but I have a few more questions. I installed the five plugs, the valves and cam shaft, and adjusted the tappets. I then installed the main bearings dry, and two of the pistons with dry rod bearings. I then used plasti-gauge on each of these bearings. My machinist had assembled the piston, rings, and rods as an assembly I lubricated the pistons and rings before inserting them. The spec for both the main and rod bearings is .002 - .003. My questions are:
For rod bearing #3 the plasti-gauge indicated almost .0015. Is this a significant deviation from spec?
For both the #1 and the #3 main bearing the plasti-gauge tappers from .002 at the front of the bearing to about .0015 at the back of the bearing. And the #2 main bearing is .003 across the center journal. Both the main and rod bearings .010 bearings. Is there a problem indicated by this data or am I good to proceed with plasti-gaugeing the other two rod bearings and proceeding?

Another concern that I am wondering, but have not researched yet, is how do I measure the run-out of the crank shaft? A feeler gauge on the side of the #2 main bearing? I understand that measuring this value is an important factor in avoiding a rear seal failure.
Thanks, Phill

So to clarify, the main bearing clearance varied from between .0015" and .002"? For reference, .0015" would be tight, but .002 would be well within spec. Note that if there are any burrs on the main bearing saddle in the block or on the cap, this could affect the clearances. It should also be noted that engine bearings generally come with a coating that wears off quickly. I always hit the edges of any bearing housing with emery cloth to knock down any burrs that may be present. I also give the bearing shells themselves a light sanding with 1000 grit sandpaper and some WD40.

How to check main bearing thrust? Should not be confused with runout. Thrust is the end play fore-and-aft of the crankshaft against the thrust bearing. This is actually more important than most people think because the amount of thrust end play can affect the oil pressure. Too much thrust end play can lower the oil pressure. I don't know what the spec is for the Cub motor, but I bet it's within .006" to .010", right? Using a feeler gauge is acceptable, but prone to faults. A better way is to use an dial indicator. I place the indicator on a crank counterweight or the snout of the crank and measure the end play that way. Any lube on the bearings will affect the measurement, so measure it dry (or with a very light amount of oil smeared on the bearing shells).

Since most engine bearing manufacturers intend for bearing end play to be "adjusted", I always push the crank forward with a screwdriver wedged between the block and the crank while I'm installing the bearing cap. This will even the rear side of the cap with the block making the two halves of the thrust bearing flush with each other. You could even install the main cap just snug and smack the crank forward with a gentle blow of a hammer.

I then measure with the dial indicator and make any adjustments on the front of the thrust bearing.

How do you adjust thrust clearance if it's tight? With light touches on a belt sander or by sanding on emery cloth.

[tst]

was the crank machined ? rods are 2-.003 did you use "green" plasti gauge? , dial indicator to measure end play for thrust bearing works well, .015 is tight, check it again , maybe machinist was off ? .004-.008 thrust end play specs are in the manual, did you torgue caps to spec when checking clearance ? are the caps in correct orientation? they only fit one way correctly

[ricky racer]

I would say that .0015" would be acceptable since it still allows room for the oil to provide a protective film but the ones that taper are a little suspect. You may want to pull the crankshaft out and recheck the bearing fits and make sure there's no dirt under the bearing halves or under the mating ends of the bearing caps. Double check to make sure the oil hole is in the correct position.

The lateral or end clearance is measured at the center main bearing by pushing the crankshaft against the rear thrust face of the center main bearing. Using a feeler gauge, check the clearance between the front thrust face of the bearing and the crankshaft. Make sure the upper center main bearing thrust face is against the crankshaft while keeping the crankshaft pressed against the lower bearing thrust face. Clearance in the bolt holes can allow misalignment.

I'm not sure what you are referencing regarding runout. There should be no, or very little runout on the crankshaft.

If the ring end gaps have not been checked, that needs to be done. At the very least, carefully remove one of the compression rings and place it in each of the cylinders and measure the end gap. If the end gap measures good you're probably safe to assemble the engine. If the end gap is too tight, you'll need to remove all of the compression rings and adjust the end gaps.

[phill_mi]

I removed all of the main bearings (and pistons), cleaned the bearings and followed the Bearing Fitting Procedure in the Service Manual more carefully. Then I torqued only M1 and checked the clearance with green plastigauge. I got .002 clear across so I am in spec on that one. I then did the same to Main #3 with only that bearing torqued, resulting in .002 (with only a slightly wider than .002 toward the front of that journal meaning starting to approach .0015). So the taper that I observed in the width of the plastiguage for #1 is gone and for #3 mostly gone. I understand that those are acceptable.

I came across this blog https://www.enginelabs.com/engine-tech/blueprint-series-the-thrust-bearing-and-setting-crankshaft-endplay/ which helped me understand the advice you folks had given regarding measuring crankshaft thrust. I obtained a dial indicator and measured the thrust bearing side clearance at .007. The spec is .004 to .008. So I did not try to dress the center bearing any closer to .006.

Now off to work on the fit of each piston and rod bearing. The machinist said that he had checked the end gap for each of the rings when he installed the rings on the pistons, but I will check this also.

[Jim Becker]

. . . Now off to work on the fit of each piston and rod bearing. The machinist said that he had checked the end gap for each of the rings when he installed the rings on the pistons, but I will check this also.

I would probably leave the rings alone. Since the machinist says he checked the end gaps, you probably have a bigger risk of breaking a new ring than the risk of a tight ring.

[ricky racer]

. . . Now off to work on the fit of each piston and rod bearing. The machinist said that he had checked the end gap for each of the rings when he installed the rings on the pistons, but I will check this also.

I would probably leave the rings alone. Since the machinist says he checked the end gaps, you probably have a bigger risk of breaking a new ring than the risk of a tight ring.

I agree if they've been checked already.

[phill_mi]

Thanks Jim and Ricky. I came to the same conclusion when I was checking the clearance on the rod bearings, I oiled the rings for a given piston assembly but left the bearing dry so I could plastigage it. I took note of how much force was required to push the piston through it's bore. After gauging each piston I concluded that the force required to push the piston through the bore was reasonable and was the same as each of the other pistons as far as I could tell. I know that the folks at CD's Engines in Hudsonville, MI know a lot more about this than I do when they told me they had gaped the rings. Since there was no obvious variation I decided to leave the rings as they were. I then reinserted each piston with assembly lube on the bearings and skirt, and soaked the rings in oil. For each piston I rotated the crankshaft to make sure it turned smoothly before inserting the next piston. I put a bolt in the nose of the crankshaft and used a short stubby wrench to rotate the crank. By using the short wrench I figured I was applying a minimum level of torque to achieve rotation. I am now debating whether to install the head to close up the top side or finish assembling the rest of the parts first (front cover and oil pump) before installing the head.

[Gary Dotson]

Where you proceed from here doesn’t really matter, I’d probably get the head buttoned up. It sounds like you have the bottom end sorted out well.

[Stoffregen Motorsports]

I'd say you've done your due diligence. Build it, fire it, let er rip.

[Cubfriend]

I removed all of the main bearings (and pistons), cleaned the bearings and followed the Bearing Fitting Procedure in the Service Manual more carefully. Then I torqued only M1 and checked the clearance with green plastigauge. I got .002 clear across so I am in spec on that one. I then did the same to Main #3 with only that bearing torqued, resulting in .002 (with only a slightly wider than .002 toward the front of that journal meaning starting to approach .0015). So the taper that I observed in the width of the plastiguage for #1 is gone and for #3 mostly gone. I understand that those are acceptable.

I came across this blog https://www.enginelabs.com/engine-tech/blueprint-series-the-thrust-bearing-and-setting-crankshaft-endplay/ which helped me understand the advice you folks had given regarding measuring crankshaft thrust. I obtained a dial indicator and measured the thrust bearing side clearance at .007. The spec is .004 to .008. So I did not try to dress the center bearing any closer to .006.

Now off to work on the fit of each piston and rod bearing. The machinist said that he had checked the end gap for each of the rings when he installed the rings on the pistons, but I will check this also.

Dressing the main thrust bearing will only increase the clearance, not decrease it. Leave well enough alone. .007 is fine. If you dressed the bearing it would be closer to .008 which is your maximum clearance.

[phill_mi]

Cubfriend thanks for straightening me out. I plan to leave it alone.

[phill_mi]

On page 1-41 of the Service Manual I do not understand this statement:

NOTE: If necessary, install a new wear sleeve onto the fan drive pulley using the FES 33-4 fan drive pulley wear sleeve installer as shown. Be sure to apply a sealer onto the pulley O. D. or the I. D. of the wear sleeve before installing the wear sleeve onto the pulley.

When I look at my pulley I do not find a sleeve, so I am not sure how to understand this.

But when I look at the idler gear I do see a bushing that appears to be pressed into the gear. I have been using the Service Manual but I don't see any reference to this bushing so that I can check the clearance. I went ahead and installed the idler gear. I did not notice any slop related to that bushing. Later I found the information on the bushing on page 10 of GSS-1008. As I read through GSS-1008 I noticed that many of the specs in the Service Manual are specified as a wider range of values in GSS-1008, with the Service Manual value typically the minimum value. Example the Main bearing bolt torque is 55 ft-lbs in the service manual but 55 to 60 in GSS-1008. A similar story for the rod bearing bolts and the idler gear bolt. While I meet the minimum should I revisit them to get into the mid range (or does it even matter for my old school snap action torque wrench)?

And on a third topic I find that some of my parts were not clearly labeled when I removed them from the tractor. Oops! So I have been looking up the parts specifications on Messicks to confirm the correct bolt, etc. But I cannot find the valve cover bolts or studs on Messicks and my memory is not clear as to what I should put in those two holes? Can anyone point me in the correct direction to look this info up?

[phill_mi]

OK I see that it is bolts that I need to find for the valve tappet cover.

[Dale Finch]

The sleeve they refer to is IF your pulley has a groove worn in it from the seal or o-ring, you can "repair" it by installing a wear sleeve (aka Speedy Sleeve) such as this one sold by TM Tractors, which comes with the correct sleeve AND seal:
http://www.tmtractor.com/new/en/472fp.htm

Here is a HOW TO showing a homemade tool for installation:
http://farmallcub.com/phpBB2/viewtopic.php?f=141&t=76098

[Bill V in Md]

OK I see that it is bolts that I need to find for the valve tappet cover.

5/16" x 3" NC Hex Head. These are identified in the Parts Manual.