FrontEngineDragsters.Org Forum
Technical => Matt Shaff's Engine Shop => Topic started by: PSweeney on July 04, 2016, 05:56:18 AM
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What kind of torque should it take to turn over a newly built SBC with a stoked crank, solid roller cam and rev kit installed ? I'm talking with plugs out but valvetrain installed
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Lot of variables. Spring pressures,ring drag and lube are just a few.I would try to find out what it was w/o valvetrain and see if you can get a comparison from there. JMO
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yeah will do, stripping the intake tonight to pull the rev kit
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Rev kit does not add that much spring pressure that would make it hard to turn over. When I installed the rev springs, I was able to do so with just my fingers (no tools or pliers)
The use of the word torque is bad without giving a value to it.
Even with the valvetrain and plugs installed, if you can turn the motor backwards to check the drag or lock-up if thats the case
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with no heads, are motors are about 18 foot lbs to turn over with cam installed. bbc or sbc i known it not much help :o
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You having problems then?
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PSweeney:
We check piston ring drag when assembling an engine.
The oil ring is what we are looking at close. That is easy to adjust with different expanders.
Too much oil ring drag takes HP to turn the engine over. Low drag oil ring sets come in at about 18-25lbs of drag.
You can run less with a vacuum pump. Some ring sets we have seen as much as 50lbs of drag. Way too much !!
The common method of checking is to put the oil ring assembly on the piston. Oil the cylinder and put the piston and pin in upside down.
Push it all the way down and pull up with a fish scale hooked to the wrist pin.
Matt
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thanks guys, all sorted, seemed a lot but wasn't much more than 100ft lbs with valve train adjusted.