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Rotating assembly turning torque

Posted By: BradH

Rotating assembly turning torque - 10/24/12 06:03 PM

This is a FWIW, since I'm not sure what sort of interest it may have.

Anyway, I put my new digital torque wrench on the crank of the 452 yesterday after doing the final "torque + angle" routine on the rod bolts and found the turning torque of the assembly "as is" (light lube on the piston assemblies and bearing lube on the crank & rod journals) measured 17-18#s.

I've read somewhere that a typical street build is 25-30#s and "real" race engines can be down closer to (or in the?) single-digits, so I think this looks fairly low-friction for a street/strip build. I've never actually checked this before on my own engines, so I don't have any point of comparison, unfortunately.
Posted By: Crizila

Re: Rotating assembly turning torque - 10/24/12 06:35 PM

Just finished a 408 sm blk build using 1/16" rings and I came up with a torque reading of 25 ft lbs. Bearing clearances were a little on the tight side. Piston to wall clearance was .008". ( forged "Icon" blower pistons).
Posted By: Performance Only

Re: Rotating assembly turning torque - 10/24/12 06:35 PM

That's a good number for rotating torque. What was the breakaway torque reading?
Posted By: BradH

Re: Rotating assembly turning torque - 10/24/12 06:52 PM

Quote:

That's a good number for rotating torque. What was the breakaway torque reading?


I set the target torque # for the wrench to 30#s and started to pull slowly & steadily on it... it "flashed" to 18#s and then looked like it settled to about 17#s for the rest of the pull. The max torque # displayed was the initial 18#.
Posted By: sixpackgut

Re: Rotating assembly turning torque - 10/24/12 06:54 PM

mine 19
Posted By: 64Post

Re: Rotating assembly turning torque - 10/24/12 07:12 PM

My last one - 16#.
Posted By: mopar dave

Re: Rotating assembly turning torque - 10/24/12 07:16 PM

my 408 is 20#
Posted By: Dap

Re: Rotating assembly turning torque - 10/24/12 07:48 PM

Will that number be any different once the rings are seated?
Posted By: Streetwize

Re: Rotating assembly turning torque - 10/24/12 07:49 PM

I usually shoot for under 20 on a steel rod motor with 1/16 compression rings. 16-18 is pretty typical. Aluminum rod motors in my experience seem to have a bit more initial drag. You can tell a lot about the motor just by setting the crank and torquing the mains. Line hones are HP.

Drives me nuts when guys insist on main studs and then want to skimp on a hone.
Posted By: Cab_Burge

Re: Rotating assembly turning torque - 10/24/12 09:07 PM

The cylinder wall finish, the ring width and tension and the lube used will affect the breakaway and rotational torque. Dick Landy told me years ago to use 20 to 23 lbs break away and 16 to 18 lbs. rotational as a way of measureing a good job I have a SB Chevy pump gas blower motor with 5/64, 5/64 compression rings and 3/16 standard tension oil rings in the shop now, that rascal is not as easy to turn as the bigger bore Mopar motors with 1/16,1/16, 3/16 oil ring with standard tension I did a bracket race motor last year that had 1.5MM,1.5MM,compression rings and 3MM oil ring, it was real easy to turn, I should have checked it and written it down It was noticably easier to assemble and turn over My next race motor may have thinner rings than that
Posted By: rickraw

Re: Rotating assembly turning torque - 10/24/12 09:33 PM

u should use a beam type torque wrench to check turning torque
Posted By: Crizila

Re: Rotating assembly turning torque - 10/25/12 12:31 AM

Quote:

u should use a beam type torque wrench to check turning torque

Posted By: perfmachst

Re: Rotating assembly turning torque - 10/25/12 04:06 AM

hi, a beam torque wrench will give you truer results. as for rotational torque, my 340, 5# to rotate, metric rings in motor.
Posted By: Rapid340

Re: Rotating assembly turning torque - 10/25/12 01:22 PM

Quote:

Will that number be any different once the rings are seated?



Yes, it will be smaller to varying degrees depending on cylinder wall finish.

Posted By: Crizila

Re: Rotating assembly turning torque - 10/25/12 03:49 PM

Quote:

hi, a beam torque wrench will give you truer results. as for rotational torque, my 340, 5# to rotate, metric rings in motor.

5 pounds????
Posted By: RAMM

Re: Rotating assembly turning torque - 10/25/12 03:58 PM

Quote:

u should use a beam type torque wrench to check turning torque



I agree although a Snap-On dial type is easier to read while in motion. That being said 17-18 lbs for a big block with that stroke is fairly typical in my experience. Working on a 705ci Chevy and it is alot more than that with a 5.3" stroke I can tell you. J.Rob
Posted By: BradH

Re: Rotating assembly turning torque - 10/25/12 09:18 PM

Quote:

... 17-18 lbs for a big block with that stroke is fairly typical in my experience.


At least it's good to know I haven't effed it up...

FWIW, this is a stock-stroke 440 + .060" w/ ~ .006" piston clearance, just under .003" rod & main clearance, conventional 1st rings, Napier 2nds and 18# oils (according to Total Seal).

My last build used their (TS) "gapless" top rings, RBT 2nds and 23# oils, so this "should" reduce the drag somewhat while still (hopefully) keeping oiling under control.
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