First, since this comes up periodically, does anyone have an estimate of the torque required to turn a freshly assembled rotating assembly in an SBC? I don't own a large enough beam or dial-type torque wrench (only 3/8" - 40ft/lb) to measure, and gauging with a micrometer type wrench is impossible. By raw "feel", I'm guessing 60 ft/lb for a fresh crank, pistons and rings with no timing chain, no oil pump, and 30W assembly lube. Any other guesses, or has someone actually successfully measured the torque?

I understand that clearances, ring selection, and the depth of the honed finish on the bores will affect this, but even guesstimates will be a start. I've measured 10-15 on the cranks alone, but coupled with the piston/rod assemblies, I have no good measurement.


Second, I know I'm out of the loop, but when the hell did GM sell the Detroit Diesel Division fo Daimler/Chrysler? Was I sleeping?

 

I've measured anywhere from 30-50 ft-lbs with a beam wrench; usually a fresh motor with street moly rings will run around 35. I'm talking about just the short block here; with the cam and properly set valves, it's about 20 more.

The crank should spin with a couple of inch pounds. I can grab the snout of a freshly installed crank with no rods, and spin it to about 200-250 RPM with one twist, and it will take a couple of seconds to coast down.

 

The crank laid in and torqued with a one or a two piece rear main seal .....

once break away is done (initial starting of motion) its one finger for a race motor or large clearance and two fingers for a tighter clearance piece.....on spinning the crank it should spin freely.

The most resistance comes from the ring package...then the flat face lifters....OEM's have been working on this for every last bit of friction reduction...look at the narrow ring packages, and shorter skirts on pistons and factory roller cams.

In the old days of drag race motors and low tension rings and mirror finished bores I got 27'# usually with no pushrods. (SBC 4" bore stuff).

Street motors with modern thin rings might approach this but I doubt it.

There will be some trade offs with low tension rings and motor longevity.......holding assembly tolerances, do your best for the intended use....ideally you want to be able to turn the complete assembled motor over with one hand....but that will never happen.

On part two...doesnt Penske own Detroit Diesel......(Ive been on the moon for 2 years.....) hell...I dont know who owns who these days.....I think Federal Mogul owns everyone else.

 

never checked but i'd guess in the 30 to 40 ft/lbs range. i have to dial type torque wrenches from snap on and they both max out at 150 in/lbs, so they'd be worthless to check with. a crank will spin with next to no effort.

gm sold detroit? allison too? never heard it

 

AFAIK, Allison is still part of GM, but Detroit is dedfinitely flying the D/C banner.

 

The spec that I read years back, and the one I've always checked with is 55 ft/lbs... maximum. More than that and something is binding. what I've observed is in the 40 ft/lb range.

Interesting note, on the old rope seal version, the turning resistance is 90 ft/lbs max! A 40 ft/lb loss from a crank seal!!

 

since my good friend roger smith left i don't have access to insider info at gm like i use to. hard to believe detriot isn't part of gm any more.

 

It appears that the 10-15 ft/lb guesstimate is then a result of the rope seal in two-piece installations. I know that on tear-downs, the cranks will usually spin like a top once the rods are freed.

As for Allison, it appears that they are still safely tucked under GM's wing, but everything changes. It seems that the only diesels being produced at GM are the Duramax light/medium truck engines and the huge inlines being made at Electromotive (for locomotives).

 

I thought those were V-16's ?? I read "Road Test" a few years back, I think it was in Car and Driver, and they tested an Electromotive diesel that was a multistaged, turboed supercharged V-16. It made 23,000+ hp at 903 RPM!! How about that for low end torque. LOL.

 

You could be right. I know the Fairbanks diesels in locomotives are inlines, mostly 6 and 8 cylinders, and have up to 16" bores with 3' + strokes. All that just to turn a generator set. And the fuel they run looks like 30W oil/mud/tar, not any kerosene I've ever seen...

 

The GM locomotive blocks that I've seen and read about have been V-16's. I'm sure there are many variations, but I'm pretty sure CN rail sticks to V-16s.
Back 25 years ago when my father was a heavy-duty mechanic, and into various types of racing, he used to tell people that his day job involved working on direct fuel (diesel) injected, roller cam, twin-turbo-d V-16's. People'd usually ask, dumbfounded, what kind of rev's they would pull too. My dad would casually respond; " 'bout 600 at cruising..."

Can you imagine dealing with an 1100 pound crank?

 

When I was in my millwright training class I got to operate a GM powered locomotive at Midwest Steel. From what I remember, they didn't make much HP but had ungodly amounts of torque but I couldn't even spin em on the track.