how much torque to crank over a good engine? - Team Camaro Tech
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post #1 of 6 (permalink) Old Apr 8th, 04, 09:39 AM Thread Starter
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last weekend, i was helping a friend put together a 302 for his 89 Mustang, when i decided to break out the old beam type torque wrench to see how much torque it takes to spin over a fresh shortblock- the little 302 with no heads on it took about 35 ft lbs. this is with new standard tension oil rings and that thick red assembly lube on all the bearings, so that had to add a bit of friction.
then, since i had the 355 from the Nova up on the stand, i decided to pull the plugs out and see how much force it takes to spin that over- it took a little less than 20ft lbs with the engine complete but with no spark plugs. that seemed pretty damn good to me, and helped to account for why the thing revs so damn fast. of course, it has those stupid race low tension oil rings and about 30,000 miles on it so it is nice and worn in, but it still seemed low- i can damn near spin it just by grabbing the balancer.
has anyone else checked to see what a "normal" engine takes to spin over? just one of those curiousity things.

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post #2 of 6 (permalink) Old Apr 8th, 04, 10:25 AM
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i have my 20,000 mile 381 shortblock on the stand now, hypers and standard moly rings. i could turn it over by hand from the balancer also. a little stiff at times but doable. i have the rod/pistons out for a piston swap now. i didn't think to put the torque wrench on to measure it.
maybe the difference is being broken in ?
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post #3 of 6 (permalink) Old Apr 9th, 04, 01:47 AM
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The value you have experienced is normal, ie, 35 ft/lb. Apply some oil to the cylinder walls.

When I assemble an engine, I install one piston assembly at a time and spin. One cylinder takes 3-4 ft/lbs. after the initial breakaway.

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post #4 of 6 (permalink) Old Apr 9th, 04, 04:23 AM
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If it takes 15#ft less to rotate your engine, how much would this equate to in horsepower at 6000 rpm? About 17.

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post #5 of 6 (permalink) Old Apr 9th, 04, 04:28 PM
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Since your engine is complete (minus plugs) I would have expected it to take more to turn it. What about the valve springs and rocker arms. You must have your rockers backed off? Just a thought, I have a 385 on the stand with no heads on it, I will try to spin it over and let you know (probably be tomorrow).

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post #6 of 6 (permalink) Old Apr 9th, 04, 11:08 PM Thread Starter
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nope, the rockers were all snugged down. all i did was pull the plugs out- with the plugs in, it is a real bear to turn due to compression.

you don't plan sincerity.
you have to make it up on the spot.

wanna hear about 20 years ago when i was too smart to know any better?
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