Ive seen worse. What does the crank look like. It appears that dirt has embedded into the soft bearing materal
Crank seems to be OK. I bought the engine advertised as low miles after rebuild. Dropped the pan and found one broken rear mains bolt. Just wondering if I need to do the bearings.
Hmmmm They are cheap. Lots of guys have rolled in new bearings I do feel better when the crank is polished/machined. Kinda just up to you.
Main bearing bolts usually don't break. Maybe old. Maybe main cap was not correctly seated. If it was mine I would replace the main bolts and install new main bearings.
Sometimes you open a can of worms. Once I had a old ford and the front auto trans seal leaked. pulled the crusomatic and the front pump bushing was badly worn. and sure enough the main bearings where loose and the crankshaft slop was the cause of the seal leak and worn bushing. So I installed new rod and main bearings. and thought I heard a pecking noise. and shortly after ward the engine started having a lot of blow by. So I swapped in a better mill I had. eventually I tore the old engine down. and several of the top piston rings and ring lands where broke. those new bearings shimmed up the pistons and the top ring was hitting the wear ridge at the top of the cyl. Me I would replace the bolt and run the 283. If is not broke dont fix it.
Bearing looks good to me. If this is a somewhat fresh rebuild, I would be thinking what else could fail. A broken main bolt is not a everyday occurrence.
Well, fresh rebuild or not you can't tell the condition of a Crank just by looking at it. If it were me and I was going any further that better be a Free motor. That broken main bolt tells volumes about the prior mechanic. Probably why it was sold off to you. The Wizzard
How on earth would you break a main cap bolt? If it were mine I'd replace all of em. Get some good grade 8 bolts from Fastenal and New bearings while your at it.
Sometimes due to metal fatuge or over torqueing bolts break. Stuff happens. I would rather trust a used OEM bolt than some new crap made some place other than the USA.
I did a little research, I guess the OEM bolts sometimes break. It looks to me like the bolt failed long ago, likely soon after the rebuild. The cap does not look like it moved. Thanks for all the input, I don’t have experience with engine rebuilds.
I can understand having a bolt fail while torquing it down. That's fatigue, once under torque it wouldn't just brake off afterwords. What made you decide to drop the pan in the first place? The Wizzard
The bearing doesn’t look bad. From a wear prospective, the babbit is barely worn and I do not see any copper/bronze showing. (Assuming it is not a newer steel / aluminum bearing - which does not look to be the case). It does show some dirt and debris running they it. That could actually be from when it was installed. If the average guy does it in the garage, you have to take a lot of care to keep dirt out during assembly. It is even more difficult if doing it upside down in the car. Nearly impossible. (You May get worse dirt re-doing it) For peace of mind, you could get some plasiti-gauge and check the clearance. Keep in mind that on a main, you need to take a hydraulic jack and push the weight of the crank shaft up off the lower cap near the bearing or the weight will give you a “false” good reading. Sent from my iPhone using H.A.M.B.
The bearing looks good to me. If it weren't for the close-up photography it'd probably look even better. I would plastigage the clearances and if within specs, call it good. Edit: Simpsonrl beat me to it.
Okay, lets just go with some blind faith. That said and more than just a few motors behind me here's my advise. Plasti-gauge is a good idea if you actually know how to use it correctly. I'm also assuming you don't want to get into another rebuild. Don't do the plasti-gauge. I also agree that the insert your showing us is just fine for a used insert. I'd run it. Extract the broken threads from the block. Go find some used Factory Main bolts (don't go to the hardware store). Re install the Main cap just snug and be sure to wipe some oil on the rear seal. Then loosen all the Main Cap bolts just off torque, not finger loose. Now find the correct Torque Spec. and pull all the bolts up less 5lbs from specs. Remove all the Spark Plugs. Now turn the motor by hand 3 full rotations. Now go back and pull final Torque on all bolts. Now rotate the motor by hand 3 full rotations again and see if it requires more pull to rotate. If all is well check torque again. Then go over them a 3rd time. Now install the Oil Pump and don't over torque it. That can stress the Main Cap and change bearing fit. So now you have a smooth rotating motor by hand. Now put the Pan on and fill it with Oil. Now remove the Dist. and hook up a manual Oil Pressure gauge and prime the motor with a Drill Motor and see what you have for pressure. If your at 30lbs or more and have Oil coming out all the push rods go ahead and Fire the Motor up and see what you have. At least you've taken some safety steps in giving it the best chance of living. The Wizzard
That sounds like a darn good procedure for assembling any engine. I hope I remember it on my next project.
Nice logical, methodical approach. I like it. Not everything should be slammed together like a NASCAR pit stop.
Wizzard, thank you for the instructions. I am definitely putting a correct bolt back in place. I was thinking a new main seal would probably be a good idea before I seal it up.
For no more wear than I see on that insert I wouldn't have any problem using what's there. Do you know how to get the top half out? The Wizzard
Do I need to drop the crank? Motor is not installed. If you mean the seal, I think you tap them out with a punch? Thanks
For the condition your Motor sounds to be in I would turn the Motor to upright position on a Stand or maybe hang it from a hoist. You need to totally loosen all Main Bolts and let the Crank drop off the inserts by 1/32 or so. then the seal can be pushed around and out of the Block around the Crank. Then you install the top half in reverse process. Then tighten up all the main bolts to press the seal up where it belongs being sure to get the ends flush to the edge of the Block. Once the top is in place then install the lower half and go through the Torque process as mentioned above. It's not that difficult to do but I don't think I'd do it. It was most likely new when the Motor was built and they are sure easier to install while up side down and the Crank is out of the Block. The Wizzard
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