C-123 scary start after rebuild

I'm doing a complete nut-and-bolt resto on my SC, and yesterday was the day to finally light the fire on the engine. I had a shop do the head, boil the block, grind the crank, etc. I finished with a complete rebuild kit from this site.

She fired right away, and after a little fiddling with an intermittent spark from the dist., and having to prime the oil pump (through the plug below the filter cover) it hummed and I had oil up to the rockers.

After less than a minute of running I grabbed the governor rod to increase RPM's, and it coughed and died. I hit the starter button, and it didn't want to turn over, almost like it was starting to seize? The new starter, battery & 2/0 cables were really spinning it over before, and now the fan would barely move when I hit the button. I walked away for the day.

This A.M. I hit the starter and she spun fine, but I'm afraid to run it.

Like I said, complete rebuild, new rod & main bearings to specs, oil pump to specs. It did fire a few times before I had oil up top, but not long, and I used a ton of assembly grease.

Should I take my chances & run it? How unusual is it for a carefully rebuilt engine to have a (potential) problem with seizing?

Thanks, Doug

Mine was tight also. I ran it at a fast idle for 15 min. Make sure the coolant is to the top and oil pressure is good.
Then let it run.

Did you have oil pressure? Did you try hand crank after it died to see how tight it was? I have a super c that was tight one time after I shut it down, and I'm embarrased to say it but I tore the motor down and the whole problem was the starter was stuck.

Dump the oil and check it for metal shavings. You will have some particles in the oil which is normal for a new engine to have. However you should not have shavings. If you find metal shaving then you know you have an issue and need to drop the pan for an inspection on the parts.

Myself I would change the oil and retorque the head. Then run the engine another twenty minutes without messing with it. Change the oil after that twenty minute run and see what you have and make your final adjustments. Pay good attention to how the engine sounds, oil pressure and temperature while you a running her. If you bought a sleeve and piston set and kept the pistons and sleeves matched up with themselves I would think you will be fine.

What kind of assembly grease did you use? If it was lubri-plate or engine oil that would be fine. I would drain the oil and look for metal particles that's been suggested. If there's a lot of metal particles I would drop the pan and take look at some of the bearings and the surface of the crankshaft journals. Be sure to retorque them if they look ok. Hal

I used Lubri-Plate for assembly. I'll check the oil for metal.

I always regretted that my shop man mixed up the pistons & jugs, although I miced everything, and they seemed the same. When I asked the folks here that I bought them from, they said (as did my shop guy)"that's pretty much a thing of the past" since the tolerances are so close nowadays.

I did measure everything, and hand cranked it a ton when it was just the block, crank & pistons, and it looked good. I'll proceed with caution.

Did you put the rings in the sleeves and check the end gap? They can tighten an engine up if there is not enough gap.

I checked everything & fired her back up. Sounds good, oil pressure pegged. I'll keep my eye on the oil for any metal.

Easy to get paranoid after all that work.

Thanks

I can relate. A few years back I had finished restoring a '48 Super A for a friend and had started it up in the garage after a complete rebuild. It ran like a top and after about 10 minutes I ran in the house to call Paul so he could hear his baby running again. When I got back out to the garage with Paul on the line the first thing I heard was a deafening silence. "I'll call you back"..... It had stopped cold and I could not budge it with the starter or the hand crank. I dropped the pan and started to methodically look for the cause, expecting the worst of course. Everything was free until I got to the governor/distributor. It turned out that a piece of casting flash, probably dislodged by the block cleaning process, found it's way between the governor pinion and the new babbitted bearing that it runs in. That small gear had a ton of mechanical advantage and stopped the engine dead. It wasn't the worst thing that it could have been and one new bearing later, I was back in business. If the link works you can take a look at the damage to the bearing.
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> ...oil pressure pegged...

"Pegged"? Extremely high oil pressure is not always a good thing. Does that engine have an oil pressure regulator?

Is it possible the rear main seal is tight? I like to really soak it upon assy.As others have commented I also had to fiddle with the starter after a rebuild. Jeff

Sounds like you're good to go. Lubri-plate is very good. A Cummins mechanic told me that someone rebuilt one of their engines and used lubri-plate and forgot to put oil in the engine.
I don't know how that happened. He said it ran several hundred feet before it locked up. Hal

Doug: Don't feel badly for being cautious. Try cranking a $13,000 stock car engine on the dyno and listen to how many strange knocks, squeeks, ticks and rattles and odors you hear. It will make you nearly crazy. mike

Having read all the other posts I'll tell my story on a WK40. Complete rebuild.Tractor isnt elec start so had to crank start it. Six cylinders are hard to crank so things had to be right to start.Finished it up and went to plowing. Used it several times had twenty or so hours on it but never shut it off unless I was done with it for the day. Then I did shut it off and tried to start it within 15 minutes later.It was stuck.An hour later spun over and started right up and ran good with good oil pressure. Anyway it had to sit for about an hour after running it to start it or it was tight. I had to take the pan back off and find the tight bearing . One rod hadnt been reconditioned.That was the fix. souns like yours is doing the same thing.