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At Cubfest Northeast a couple weeks ago, we were rebuilding an engine that Cecil had bored to .040 and had a crank polished. All the parts were available in one place or another, so I proceeded to put it together. Keep in mind that the block, crank, cam, and connecting rods all came from different motors.
When I installed the first piston assembly i noticed it was a little tighter rotating than usual, and that trend continued to the last piston. So tight, in fact, that rotating the engine was difficult.
I began to suspect that the crankshaft was from a 154 engine and the rods were of the old type. the difference is that the rod bearings on the newer connecting rods are narrower by about .125. Dissassembling the connecting rods from the engine confirmed that the old style rod bearings were scuffed on the outside edges - telling us where it was binding the motor.
Yesterday during hurricane Sandy I reassembled the engine with 154 (new style) connecting rods and narrow rod bushings to match. The result? The engine turns normally for a new rebuild.
Larry was looking for a part number change on the crankshaft to support my theory, but could not find one. Nor have i seen a reason for the change in rod bearings. If anyone has additional info, i'd like to hear it. One thing for sure, the newer crankshaft is not as tight a radius cut in the rod journal, and it was that extra material that was binding the motor.
The rods are different not the crank I believe Did you check the rod #s
all the crankshafts are the same as far as measurements / specks. There were some that were forged steel instead of cast steel but specks are the same. The only difference in the numbered series c-60 is the rods. 251246 is the old style rod. . the new style rod number I dont have right at hand. Usually the new style numbers on the rods cant be seen. The later rod takes a different bearing. If you happen to use the 251246 rod bearing in the later rod it will be too tight. If you use the later rod bearing in the 251246 rod it will also be too tight.If skuffing on one side of the bearing is found that usually indicates a bent rod or improperly ground crank. also the rod cap numbers must match. even if they do this doesnt insure they are a matched set. when the caps are torqued you should not be able to feel with your finger nail a difference in mating surface between the rod and rod cap.
Collector of Farmall cubs and cub cadets.Injoy helping people keep their cubs running. Years of experipnce.
the new rod # is 527457R1
251246R1 is the old rod
I surely would have bet American dollars that there was only one crankshaft, but there are two different part numbers. The break is at 261717 engine serial number. It may have only been to differentiate which connecting rods??
1971 Cub (Rufus) 1950 Cub (Cathy) 1965 Lo Boy Fast Hitch (Nameless III) 1970 Cub 1000 Loader & Fast Hitch (Lee)
The catalog only lists the crankshaft as a package that includes the rod bearings. Thus 2 different numbers even if the crankshaft itself is the same. Some of the early catalogs did show the number of the crankshaft itself, even though you couldn't order it. I don't know if there is an edition that lists the crankshaft number that was packaged with the later rod bearings. Maybe after Rudi's server is back up we can check another edition or two.
Anybody have an edition of the parts catalog from just after the rod change?
The way I interpret ENG 1 is that there are 2 packages- one each for old and new rods. The package for the old rods states that for service replacement rods, the new rod and bearing must be ordered (old rod obsolete) and that the bearing with the "old rod" crank kit will not work with the new rods.
I am glad that Betsy's mill is going to live I am sure Cecil will be happy. It was sad to see all that work go for naught at CubFest Northeast .. but I sure enjoyed what little of the engine work I was able to see. I learned a lot by guru-gazing
all i can make out on the crankshaft is 456R1 with the 4 being hard to tell. there are numbers in front of those, but they go off the casting. that number does not show up in TC37F for those packages.
The crank is STD, simply polished for this install. the scuffing on the edge of the old style connecting rod bearings was on all 4 bearing sets, so i discounted having a bearing cap mismatch issue. generally a mismatch would show with scuffing across the bearing at the joint between the cap and rod.
It appears that less attention was given to the radius on the outside edges of the rod journal after SN 261XXX, due to the increased clearance by the narrower rod bearings.
The original standard crankshaft was 251264R1. With the dowel in place it was 251264R11. The R1 number should be cast into the part (never checked one though). Your partial number seems to indicate that the crank itself did have a part number change.
the mystery deepens....
I checked 3 cranks i removed from 154 engines sn > 261XXX. all three had no part number markings evident, nor even an IH logo. it is evident by simply holding the wide early bearings up to the rod journals that these cranks also cannot accept early connecting rods.
early crankshafts CAN however accept the later connecting rods (narrow bearings) without issue, but not the other way around.
it still begs the question - why was the change made?
When I bring my two blocks down to pull the front pulleys we will have a 1950 and 1976 crank to compare side by side.
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