Technical Flathead rotating assembly tight - pointers please

Glad you found overtorquing was the problem.
What was the condition of the main bearings when you inspected it?

 

Good job locating the problem area. If it were me and it wasn't re***embled yet, I'd plastigage the mains to check oil clearances. Don't want to spin a bearing due to lack of correct oil clearance.

 

Everything looked really good with a light coating of oil. The only issue that I saw was there was some surface rust on one of the counterweights.

 

If the engine still has the floating rod bearings, these are likely to be your problem. Two rods per crankshaft journal. These are hard to find nowadays and they are not always easy to set up. Someone may have put the wrong oversize in there. You need to measure the crank journals to see if it's been reground and how much undersize it is, if any. The NOS rod bearing shells are not normally stamped with an undersize ID number. You need .oo15" to .025" clearance on each side of the bearings. The bearings float, meaning they not only turn on the crank but also turn in the rod big end. A stubborn engine can be difficult to set these up properly and some expertise is required to get it right. If it was my engine I would use an 8BA crankshaft and rods in it. It fits right in and uses precision fit bearing shells. Probably too drastic for you. To make this modernization, you must use the original timing gear on the crankshaft. The 8BA gear teeth are angled in the opposite direction and won't work. Original main bearings with this. They have a larger lock tab than the 8BA but the bearings are the same diameter. Anyway, enough of that. There's a 50/50 chance that the ring end gaps were not checked when installed. The could need the ends filed to get the proper clearance. You really need to get a service manual to help you get these things right. They're readily available from early V8 parts vendors. Make sure you get the most detailed manual available. Please don't try to turn the engine. Take it apart and find out what's wrong first. These engines are getting too scarce to risk damage.

 

Per what Glenn said above, one can suspect by how things were done (like the way the relief was ground in), that the engine may have been built by somebody who wasn't all that concerned about the details or didn't have the experience/tools for performance work.

Since you have the engine out of the car, why not take it all apart and have all the clearances checked with precision mics, check all the bearings out, maybe touch up the valve seats, etc.. You've already taken it down this far - maybe complete the job and know exactly what you have?

 

In looking closer, another concern of mine is the rods nuts . . . they look to be hardware or Grade 5 Nylocs. I've not seen rod nuts like those used on a car before. You can tell how some of them are distorted that the socket would not go all the way down on them, so they used as much of the nut as they could with a socket that only picked up about 1/2 of the flats. The way the nuts distorted also tells me they are probably not high-grade automotive stuff. If a rod nut lets go - bye bye engine.

 

Yeah, this could go south quickly. Those nuts do look completely wrong.
For the want of one book and $100 in gaskets, I'd check everything. Won't take too long - you're most of the way there, and might require no other parts. Posting some more detail pics here will ensure the parts are correct and oriented correctly.
Too pretty of an engine to chance it IMO.
D

 

Also, it appears to be missing the rear breather baffle tube (slides in under the fuel pump - into the receiver hole in the block valley). Is is very important for the crankcase breathing system to work as it should. You can probably pickup one from Mac VanPelt or Thirdgen.

 

Over tightened main bearing caps? Watched your video I can see a good amount of rust on the crankshaft surface. That rust is going to contaminate the engine oil once the windage begins as the engine runs that's going to mess up the bearings eventually. Like others above have already written you should take this apart and see what you actually have.

Ronnieroadster

 

I've never seen over-tightened main caps cause a crankshaft to be locked up . . .

 

agreed, I could be completely wrong here but I would think that any over tightening of cap bolts would just stretch the bolts, no? Once the cap is down all the way, it can't go any further.
This is ***uming the bearings are correct for the size of the crank.

 

Exactly, and the reason I suggested plastigauging the mains. There's trouble coming, I'm afraid. Incorrect bearings, housing bores out of spec, caps in wrong position, crank journals incorrectly ground....something.

 

Let me take the engine off your hands . I’ve got two 283 sbc that need rebuilt that I’d trade you straight across. I’d even toss in a 261 Chevy six for Your troubles. Just making noise . Lol
Sounds like Your getting lots of good advice for guys with experience. I’m watching this thread with much interest. I’ve got a 47 flathead that needs tore down and rebuilt.