My father in law and I are rebuilding a 455 for his 65 skylark and we've run into a problem. The engine we got had already been "rebuilt" when we got it but we tore it down anyway because it had been sitting in the open for a long time. It had indeed been rebuilt and had all new bearings, .30 over pistons and the crank was turned 10/10. Now that we've started to put it back together it's so tight I can't rotate the crank now that the ords and pistons are in. I pulled it back apart and used plastigage on the rods and mains and everything is within spec but the more rods you torque down the harder it gets to turn the crank. I'm no wus either, I'm talking it takes well over 200 ft/lbs or torque to turn it an inch. I was careful when I took it apart not to mix up the direction or the rod caps but maybe they were wrong to begin with. I have the little notches that the retains the bearing on the same side of the rod. Is that right? I took one of the rods out and installed and torqued it backwards (So the piston would be in the oil pan area) so I could move it up and down and it took a decent amount of force to turn the rod on the crank. What could be the cause of this problem? Help! Thanks!

Did you keep each cap with it's associated rod? You can't mix&match the rod caps. You can't mix&match the main caps either, they have to go on the same place they came off...

-Bob Cunningham

I have the same problem with a 305 I just rebuilt. When i moved #1 to TDC to install and time the camshaft properly, it rotated easily through 2 crank rotations, but as soon as i put the top half of the motor back on and put the plugs in, the damn thing won't budge at all.
I used assembly lube on every moving part from top to bottom and I'm told most chevy v-8s are non-interference engines, so this eliminates the valves touching the pistons (which can't happen if the cam is timed properly right?)
I've tried using a prybar on my flywheel teeth and using the engines starter and nothing will move this motor! HELP!

No I dodn't mix any of the rod caps up, I'm just not sure they are on the rods correctly. Maybe someone remembers if the two bearing tabs are supposed to be on the same side of the rod or opposite sides? As for the main caps I don't remember what order they were in but they are numbered and I have them in 1-2-3-4-5 from the front of then engine back with the arrows pointing toward the front of then engine. I don't think it's the mains tho because the crank spun just fine before I put the rods in. I'm thinking maybe I have a rod side clearance issue. That's what I going to check as soon as I get some feeler gagues. Does anyone know how hard it should be to turn over a rebuilt short black 455 so I know when I have it right? Thanks.

My 455 took 30 ft-lbs to turn after it was rebuilt.

Don't know what the side clearance should be.

The rod bearing tabs always line up on the same sides of the rod and cap. If not you will spin a rod bearing for sure. On my motors I always make sure there is a little lateral movement in the rods on the crank after they are all torqued down. Also, on all rods and caps the factory has stamped numbers. Be sure the cap number matches the rod number. One last thing I would check would be the crank alignment. If it is out it will need to be line bored.
Jim

Lark, (Name ???)
Does the crank turn ok without the rods on ? That is the first thing to check to eliminate the main bearings. If it turns ok...are you sure you have the pistons in the correct locations ? If not, it can lock the crank up like you say. The numbers stamped on the rods should face the oil pan rails, and the notches on the pistons go to the front of the engine. If you have the numbers facing in towards the center of the engine, that is probably your problem.
By the way, I am not sure, but is a Buick like a Pontiac where looking from the bottom, the first rod in the block is actually number two ? If so, that is your problem. The number 1 piston and rod assembly should definitely be in the front, drivers side, cylinder.
You should be able to turn the engine over with a 3/8" drive ratchet. If you can't .. dont force it ... you are messing something up if you do. You cannot build engines with the "get a bigger hammer" mentality.

Lark,
Just wondering if you found the problem with your 455. Nice to know the solutions so we can avoid problems in the future.