Timing chain slack

[ctomkins]

Has anyone turned their engine over by hand and seen the timing chain go slack when compression seems highest.

Maybe this is just indicitive of high compression engines when cranking with a wrench because my other engine that I know has no problems does the same thing..

[oinojo]

Has anyone turned their engine over by hand and seen the timing chain go slack when compression seems highest.

Maybe this is just indicitive of high compression engines when cranking with a wrench because my other engine that I know has no problems does the same thing..

my motor as of now is doing the same thing... im on the #2 lobe on the cam sprocket for cam timing.

[a7dz]

Don't mess with the chain the tension is controlled by oil pressure. When turning by hand you have no pressure against the chain.

[oinojo]

Don't mess with the chain the tension is controlled by oil pressure. When turning by hand you have no pressure against the chain.

so i should be fine? if so that would make my life a whole lot easier:)

[ZSaint]

If the chain was tight when new, the camshaft must be retarded when the chain stretches, right? Going to the #2 hole advances the camshaft, correct? I am just checking my thinking on these camshafts. Confirmation?

[MikeW]

My recollection is that changing the hole simply puts more tension on the straight side of the chain. The tensioner, which is both spring loaded and controlled by oil pressure, should always take up whatever slack there is on the other side while the engine is running. I agree that the tensioner has less effect when turning it over by hand. Does that make sense or am I completely losing it?

[Ed]

Are you turning the crankshaft bolt in the clockwise direction?

[oinojo]

Are you turning the crankshaft bolt in the clockwise direction?

yes, i am rotating clockwise.

[jmortensen]

You've got two forces resisting you when you turn the engine by hand. The compression and the valvetrain. It seems pretty clear to me that you a point in the valvetrain where it wants to move forward, and the crank doesn't. No big mystery.

FWIW, you might want to move the slack side guide to take up as much of that slack as possible, keeping the angle so that the chain hits the bottom of the chain guide as smoothly (tangentially) as possible.

[montoya_fan01]

My recollection is that changing the hole simply puts more tension on the straight side of the chain. The tensioner, which is both spring loaded and controlled by oil pressure, should always take up whatever slack there is on the other side while the engine is running. I agree that the tensioner has less effect when turning it over by hand. Does that make sense or am I completely losing it?

I don't really see how this could be correct.

No matter what cam locator hole you use, the number of links between cam gear and the crank gear remains the same, and the tensioner is always going to take up ALL of the slack in the chain. There should be no difference in tension (all other things being equal).

From what I can see, changing to the #2 or #3 cam locator hole will ONLY change the point(s) at which the valves are operated in relationship to the position of the crankshaft/pistons. (i.e. advancing the camshaft in 4 degree increments in relation to the crankshaft/piston(s) operation)

Does that make sense or am "I" completely losing it?

[MikeW]

I think we're really saying the same thing. Clearly the 3 locator holes are provided to compensate for timing chain stretch. If the stretch is not compensated for indeed the valve timing would be off. The point that I was trying to make is that the stretch only is a problem on the side of the chain that is straight and under tension. It's that side of the chain that's actually doing the work. The other side of the chain is getting a free ride back via the tensioner side - you can't push on a chain. You could "stretch" the chain by adding a new link and that wouldn't really hurt anything as long as the tensioner can compensate. If the side under tension is actually stretched (where individual links become slightly longer) the angular relationship between the two sprockets is affected.

[montoya_fan01]

Still, I do not see how you can say "changing the hole simply puts more tension on the straight side of the chain." Yes, using a differnet locator hole will maintain optimum angularity between the two sprockets, but it neither increases or decrease the "tension". If one were to measure "tension", it would be the same no matter which of the locator holes was being used (using the same chain, gears/sprockets). The tensioner will take up ALL slack until it's limits are exceeded.