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00transamnh 
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Location: Maine
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 Topic: Connecting rods pinching crank
Posted: 15 Oct 2016 at 6:33am |
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Gentlemen I need some help.
I am rebuilding a 1940 B engine and have run into a roadblock. After installing the rod bearings and caps when I approach anything close to spec torque the crank is pinched to the point that i can not rotate the engine. The mains came out perfect but these rods are killing me...
For some background this cam was ground .010 under and I am using .010 under clevite bearings. I am also using a full .010 shim stack (and even used .012 to see if it would give relief). Also the caps and rods were kept together so i am confident that is not my problem. A plastigage. tells me i am right on at the top of the bearing with .002 clearance.
Any idea what i can look for here? I am stumped.
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Tim NH
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Location: Lancaster NH
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Posted: 15 Oct 2016 at 6:44am |
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Make sure the shims are back as far as they can go from the bearings. Tim
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1950 WD 1959 D14 1955 WD45 1976 7000 B 207
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00transamnh
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Posted: 15 Oct 2016 at 6:59am |
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Tim, they are not in contact with the bearings.
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Hubnut
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Posted: 15 Oct 2016 at 7:25am |
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Sometimes plastigauge can give a false result. Increase the shim in increments and retest. I bet you find similar clearances and it will unbind the crank.
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1940 B "Lucy"
1941 B w/ Woods L59 "Flavia"
1942 B w/ finish mower "Dick"
1941 C w/ 3-point "Maggie"
1947 C SFW w/ L306 "Trixie"
1972 314H
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Gerald J.
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Posted: 15 Oct 2016 at 7:29am |
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Make sure the rod caps are turned the same way they were when they were bored. A reversed cap can be as much of a binder as the wrong cap.
Gerald J.
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00transamnh
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Posted: 15 Oct 2016 at 8:01am |
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Are the rod bolts match machined with each rod and cap? I have definitely mixed up the bolts at this point. Could that be my problem?
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00transamnh
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Posted: 15 Oct 2016 at 8:06am |
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Gerald, the caps on these rods are fool proof. They only go in one way.
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TramwayGuy
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Posted: 15 Oct 2016 at 8:57am |
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Were the rods resized? Perhaps they are out-of-round. They may have clearance in one direction but not at 90 degrees.
You need to torque the caps onto the rod; then measure with inside micrometer at several locations. Wouldn't hurt to double check the rod journal also.
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fixer1958
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Posted: 15 Oct 2016 at 9:01am |
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Can you check them one at a time to kind of narrow down the offending rod journal?
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00transamnh
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Posted: 15 Oct 2016 at 9:38am |
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It appears that cyl 1 and 4 are my problem children. 2 and 3 seem to rotate freely.
The engine was seized but the rod bearings appeared to be in a less than catastrophic state.
Going to pull out cyl 1 now and see if i can spot an out of round condition.
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Don(MO)
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Posted: 15 Oct 2016 at 9:51am |
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Did you read the part in manual about installing rod/piston units, please read it, or just turn the 1 and 4 rods around 90* and check the fit.
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3 WD45's with power steering,G,D15 fork lift,D19, W-Speed Patrol, "A" Gleaner with a 330 corn head,"66" combine,roto-baler, and lots of Snap Coupler implements to make them work for their keep.
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Dick L
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Posted: 15 Oct 2016 at 11:06am |
Common problem actually.
Do you have the ability to measure inside and outside dimensions? If you measure the crankshaft journals. Then put two rod caps together with the bearings installed with bolts finger snug to make sure you get a good reading, then measure the inside. If you have more than .0035 difference you will need to file the ends of the bearing shells. When you have more than the .0035 or so the bearing ends have no other place to go except in toward the journal.
How I fit and file when this happens.
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Dick L
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Posted: 15 Oct 2016 at 11:15am |
I think I am changing my opinion on what you have going on. Do you have the rods all going the same direction? The rods are off set and need to be installed with the narrow side toward the main bearing caps. If thay are in wrong the rod will be cocked. The problem would be pinched by the above post or in the rods put in the wrong direction.
The picture at the link is how they go.
Edited by Dick L - 15 Oct 2016 at 11:19am
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00transamnh
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Posted: 15 Oct 2016 at 11:57am |
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Figured it out gents! Atleast for cyl 4.
First, the rods were in the right direction, so that wasnt the problem.
After pulling the #4 piston and rod out I did the roundness check and it was WAY out when i torqued it. Oddly enought when untorqued everything seemed to be ok. It was like the entire cap would shift in one direction when torqued.
After some close examination i noticed that on the rod, the mating sirfaces for the bolts had some rolled over material. When torqued the D shaped rod boles would rotate and ride up and over the roled over material. This caused the bolts to cross-corner and drive the rod and cap in opposite directions. A little filing and a good clean and Im back in business.
Edited by 00transamnh - 15 Oct 2016 at 7:07pm
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Dick L
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Posted: 15 Oct 2016 at 3:40pm |
 00transamnh wrote:
Figured it out gents! Atleast for cyl 4.
First, the rods were in the right direction, so that wasnt the problem.
After pulling the #4 piston and rod out I did the roundness check and it was WAY out when i torqued it. Oddly enought when untorqued everything seemed to be ok. It was like the entire cap would shift in one direction when torqued.
After some close examination i noticed that on the rod, the maring sirfaces for the bolts had some rolled over material. When torqued the D shaped rod boles would rotate and ride up and over the roled over material. This caused the bolts to cross-corner and drive the rod and cap in opposite directions. A little filing and a good clean and Im back in business. |
You lost me on that one but if you have it working all is well.
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Tracy Martin TN
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Posted: 15 Oct 2016 at 6:58pm |
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Dick, I think he means under bolt head was causing a shifting problem. A good spot face with counterbore would cure it. HTH Tracy
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No greater gift than healthy grandkids!
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00transamnh
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Posted: 15 Oct 2016 at 7:09pm |
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Exactly... type-o in my post fixed (typed maring rather than mating)
Edited by 00transamnh - 15 Oct 2016 at 7:25pm
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