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Re: Crankbolt - loosening & tightening
On Wed, 2 Oct 1996, Graydon D. Stuckey wrote:
> -Combustion pressures produce enough force to produce the rated
> output plus friction and other losses. Each cylinder would be
> approximately 1/5 of the total output. My gut feeling is that this is
> approximately the force that you would exert on the piston by cranking on
> that crank pulley bolt. I will check my engine design texts tonight if I
> don't forget. The simple way is to start with teh BMEP (brake mean
> effective pressure) for a rough estimate of the force that the piston
> sees under normal use. I just don't remember what this number usually
> works out to for this type of engine.
Well I have a couple of issues on this one, but most of all:
A) Graydon has NEVER been wrong
B) I have been.
Keep these in mind.
OK, rope, I personally would not do that because an average person with a
breaker bar or torque wrench can produce more torque than the engine can.
Dont beleive me? Put your manual tranny in gear, stomp on the brakes, and
have someone tighten that nut. You wont get very far without slipping
your clutch. Now if you can exert more pressure than the engine can, what
are you doing to the rods or the bearings, or even the head and bolts?
The other reason is what if a small peice of the rope were to get behind
one of the open valves, and as you push your piston up....(You get the
Also... Even if it is the same amount of cylinder pressure you are
exerting as when the cylinder normally fires, it doesnt mean its the same
thing. The rope will not give even pressure to the head and walls like
normal combustion. You will have 'pressure hot spots'.
Then you ask... "Then how do I tighten it?" Ive always used loctite and
an impact. Set it to max and drive it in using as much thread as possible
(Give it a running start). You should easily exert the required 225
lb/ft. Besides, it wont loosen, thats the way the engine normally turns.
(Refer to letter A above)
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