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How much to turn?
I am building a 400 sbc.I remember a long time ago a engine builder Iknew said it should take just so much torque to turn a short block assembly.I was just wondering if anyone has heard of this,and just what it should take to turn one? Using my torque wrench on crank snout it takes between 18 / 20 ft lbs.
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Is that the break away torque or the turning torque? Every engine is different based on ring tension, ring thickness, cylinder diameter, assembly lube used, double or single lip seals. You see my point. It's not always just a straight forward number to cover them all.
That said if that is your break away torque it is probably just fine for a street / bracket type engine. JMO Curtis |
Yea I guess it would be break away torque. I see your point last time it was a 355 different bores,rings,ect. Thanks
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Originally Posted by curtisreed
Is that the break away torque or the turning torque? Every engine is different based on ring tension, ring thickness, cylinder diameter, assembly lube used, double or single lip seals. You see my point. It's not always just a straight forward number to cover them all.
That said if that is your break away torque it is probably just fine for a street / bracket type engine. JMO Curtis |
turning
BBC short block only turning torque around 25-30 with std. tension 1/16 rings.
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Cylinder finish plays a key role in both break away and turning torque.
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What's the point? All the engine builders that I considered as "good ones' advocate turning the crankshaft assembly through several rotations so that the rings (in completely dry cylinders) will begin to seat.
Most modern racing engine builders will tell you that after about 5 revolutions, if you honed the cylinders correctly and they're straight, 75% of the "break in" or seating of the rings will be accomplished. The last 25% requires heat and compression to finish the job . . But that's what I've been told over the years and some of you may have different ideas or mentors . . And once you have turned your crank assembly four or five revolutions the torque readings will (or should) change . . even the breakaway will be affected . . The numbers? Whatever you end up with, but it certainly shouldn't require MORE torque to any degree . . And without the full assembly, the crank should spin by just twisting the rear crank flywheel flange with your fingers . . If it doesn't, your bearing clearances are too tight! |
Originally Posted by roadkill2
And without the full assembly, the crank should spin by just twisting the rear crank flywheel flange with your fingers . . If it doesn't, your bearing clearances are too tight! |
Well, Yeah . . !
heh, heh, back in the day, I had a buddy who built 392's for a couple of the T/F FEDs in the area and he assembled them with 50 weight. On a cold day you couldn't turn the damned things over with a 6' cheater pipe on your breaker bar . . First time he used white lubriplate on one he went back and took it apart to recheck the bearing clearances. . he said , at first he thought he had left the bearings out of it . . . When I think of all the dumbassed stuff we used to do, because some hot shoe told us that's what he did, I wonder how I kept from either shooting myself for being so damned stupid or grenading everything I ever touched . . . Very flat learning curve . . heheheheheh |
I learned later $$$$$ in life not to believe EVERYthing another 'racer' told you. They'd lead you up the wrong stream and laugh their a$$e$ off at your expen$e . Funny now but shor weren't then ! :roll: :oops: :oops: :oops:
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