Have a guy who thinks he has a issue with his engine it takes 70 ft lbs to role it over with no spark plugs in it.

big block 500 inches small roller cam in the car hooked up ready to run. To be honest I have never checked mine.
what's your role over at??

Have him remove the rocker arms and spark plugs and see how much break away and rotational torque is needed. Dick Landy told me years ago to look for 21 to 25 ft. lbs break away and 15 to 18 ft. lbs rotational both ways EDITED: That was on a new short block with standard rings back then, 1/16,1/6, 3/16 low tension oil rings with a fairly rough bore .Once the motor is ran it will turn over a lot easier with broken in rings and cylinder walls My last bracket motor ended up having 1.5 MM,1.5 MM and 3.0 MM oil rings with really smooth cylinder walls I didn't think to measure it for breakaway and rotational torque but it was way easier to turn over than the same combination in a different block with 1/16,1/16, 3/16 standard tension oil rings

This might not be of help because I only have a freshly assembled 512 short block with std tension rings to go off of, but I can turn it over fairly easily with a 10" ratchet. ~30 ft lbs break-away tops, and I used assembly lube, not motor oil.

Depending on the rockers (bushed vs needle rollers) and different valve spring pressures for a specific combo, I would imagine that a long-block's rotational drag could vary quite a lot from engine to engine.

On my SBs.. I have measured 3 of them.. my race engine was
16 pounds(405ci with 705 roller,springs were very stiff..
my back engine 396ci .640 roller but with lesser springs was
24 pounds... my hot rod engine is a 416 with a .640 roller..
springs are 260 seat.. that one takes 28 pounds

My SB engines are about the same as Mr.P but smaller cams and normally hydro rollers in most of my builds.

I measured them out of curiosity but have never heard a spec. There are a lot of things that should be factored in and would be hard to predict, ring tension, ring thickness, bore, stroke, cam type and spring pressure, what kind of assembly lube (I use oil except on a flat tappet I use STP on the lobes and lifter foot)bearing clearance in rods, mains and cam...

360 with 5/64 Mahle std tension rings 16# break away. This was just the short block.

Checking while turning the valve gear means nothing. That's all a function of the cam. Some motors, with the cams we run, you need a SERIOUS cheater bar to turn it with plugs in it and not much better without. You ALWAYS have spring pressure on the cam fighting you both ways. Plus he is also turning the coverter

I take my readings just after dropping in my lifters and prior
to installing the rockers and never with the plugs in

Short block hemi wihtout cam and timing chain was 17ft lbs. Once I installed cam and timing chain, and dropped in lifters (but no rockers or pushrods)it went to 21 ft lbs. It was under 25 ft lbs which is what I read should be a good number so I was happy. It is a lot more now that I have rockers and valve springs installed.

I don't think that's anything to be concerned with. My 604 Predator with 55mm babbit cam bearings took over 140 ft pounds to turn over without plugs.