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  • Engine: Hard starting when warm update

    I posted this issue some time ago about my 259 will not start (turn over) when warm. There were several suggestion relating to electrical issues, however I had eliminated starter and electrical components and therefore I had determined and internal problem such as rings too tight. The engine has been disassembled and the problem has been determined to be the connecting rods. The bearing shells were scrubbing on the crank throws when warm and clear when cold. It has been determined that the connecting rod cap end is out of round and therefore is oval shape causing the binding. The machinist is going to re-true the cap end to make it round. It was explained to me that years of reciprocal action can render the rod ends out of round. The bearing shells have about 12 hours running time on them and will need to be replaced. This was somewhat of a set back but a good learning experience when dealing with older enginesClick image for larger version

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  • #2
    Originally posted by altair View Post
    I posted this issue some time ago about my 259 will not start (turn over) when warm. There were several suggestion relating to electrical issues, however I had eliminated starter and electrical components and therefore I had determined and internal problem such as rings too tight. The engine has been disassembled and the problem has been determined to be the connecting rods. The bearing shells were scrubbing on the crank throws when warm and clear when cold. It has been determined that the connecting rod cap end is out of round and therefore is oval shape causing the binding. The machinist is going to re-true the cap end to make it round. It was explained to me that years of reciprocal action can render the rod ends out of round. The bearing shells have about 12 hours running time on them and will need to be replaced. This was somewhat of a set back but a good learning experience when dealing with older engines[ATTACH=CONFIG]62360[/ATTACH].
    I have been to several rodeos, and a county fair, but I ain't NEVER seen nothing like that!

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    • #3
      This was a first for me to, but the machinist (who has some miles on him) was not surprised and commented that this is common in older engines.

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      • #4
        All 8 rods?

        Was it previously a decent running hi mileage engine?
        Or, was it built of bits and pieces?

        I see a "holiday" off to one side near the squirt hole representing a low spot in the Big end bore, and about 180° of heavy contact, like there was pretty much zero clearance.
        If 2 rod caps were switched one of the zillion possible results might be one too small Big end, and one too large Big end.


        Was a check with Plastigage made when assembling the rods 12 hours ago?

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        • #5
          Well... Since the engine is disassembled there does appear to be some "scuffing" but nothing as bad as I seen that were simply cured with a set of new inserts.

          However since the engine is apart, truing the rods is not a big deal and all eight rods should cost no more than $100 or so. Also, check the engine bore for the suitability of a set of standard, (or whatever size rings are currently installed), for a direct replacement set.

          Generally speaking, any engine with less than 100 K should fall into the overhaul category meaning that bearings and rings should be able to be replaced with standard size new ones. Studebaker engines are made of much better material than the standard Detroit crap is a major consideration...

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          • #6
            I can't confirm for sure if I used plastigage I think I did, but with a standard crankshaft and standard shells I would have presumed a standard fit. The engine was rotated with no binding at the time of assembly. The cylinders were honed with new rings and they are still in good condition. This engine did not leak or smoke, there were no unwanted sounds, valves tappets were all quiet.

            I only inspected one rod, I did not look at the other seven so I don't know the condition of the remainder.

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            • #7
              Hate to be a wet blanket, but I am not buying the explanation. Not saying it isn't going to be productive to get everything perfect. Also, not saying that the rod ends may not be perfectly round. But, I don't see anything that would cause so much friction that you would have a hot start issue.

              Here is where I have an issue: "The bearing shells were scrubbing on the crank throws when warm and clear when cold." The rod ends EXPAND when hot, making for more clearance, not less. If anything, they would be tighter when cold. And yes, I understand that the crank pin also expands slightly, but not as much as the rod does.

              Don't be shocked if, after it is all back together, you still have a hot crank issue. Of course, there may be something else binding when it gets hot. Hopefully it is found and corrected during the rebuild. How is the thrust bearing clearance?
              For the record, I would be very happy to be wrong and eat crow.
              Last edited by Lynn; 02-25-2017, 04:18 PM.

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              • #8
                I'm with Lynn on this one. examine sides of rod, are they turned round on crank? you could be suffering from "Radius Ride" if so. a rod that is round wont let you set bearing in place, you have to lay keyed end it place then spring insert in to get in place without scraping backside. if bearing falls in place you have an egg shaped hole. keep looking. Luck Doofus

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                • #9
                  I can remember in high school some moons ago where we had a crankshaft with a piston and rod attached with 30 weight oil, the rod and piston was held at right angles and let fall and it dropped at a moderate to slow speed. The cap was removed and 50 weight oil was used and the rod and piston could not be pushed down. It doesn't take a lot to tighten up an engine. I am patiently waiting for my next report from the machine shop and I will post it. Thanks for the interest and comments.

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                  • #10
                    Someone filed a cap to pull that off. remember there is oil clearance between journal and bearing,,,,,usually. Doofus

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                    • #11
                      In reviewing 3 different engine/connecting rod rebuilding/reconditioning sites there appears to be a common opinion that connecting rods can be twisted, bent and out of round and usually require reconditioning depending on the application. This may require re-bending back to spec, grinding the caps and honing the bores. It is probably good practice to have these issues confirmed before assembly. Some of the comments are related to rod clearance, oil passages restricted and engine failure, (seizing). Therefore it appears that there is some validity to the machinist's claim/diagnosis.

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                      • #12
                        After looking at the remainder of the bearing shells there was evidence of 5 rod shells scrubbing on the crank shaft, that would be sufficient to seize the engine.

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                        • #13
                          Well something is wrong, the shells shouldn't be wide enough to scrub the crank, before the rod ends contact the throws themselves. Good luck figuring it out.

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