Cam timing... cam turning with no pin. What am I doing wrong?
 

I've read this procedure so many times I can do it in my sleep... and have been for a week.

So I'm finally ready to time the cams, but every time I pull the pin and turn the crankshaft the cam moves too (ie with the chain as if the pin were still in place). The only thing that seems to help is loosening the tension on the idler pulley. However, I have to make it so it's just barely holding the chain up - with no real tension. I've tried putting oil on the cam and between the sprockets, but that hasn't helped. I pulled the chain and the outer sprocket spins freely on the cam sprocket with seemingly no serious friction.

What am I missing?

Sometimes that just happens. I usually find a gloved finger on one of the lobes (on cyl. #2,3,5,6) through the cam tower is enough to keep the cam from moving, while I (or an assistant) turns the crank. Best of luck getting it squared away.

Scott

I figured that one out... but when I pull the pin the cam spins off from where it was set. When I was ordering tools I was glad I had the later style, but now I'm thinking it would be nice to be able to use the cam tool to hold the cam in place.

Right, I understand what you are asking...

When you turn the crank there is no mechanical link to the cams, ie. no reason (like the pin locked in) *why* the cam should spin--it's not supposed to. It is just "sticking" (very technical term). The way I deal with it is I just hold my finger against the lobe on one of the other cylinders, and I hold the cam while I slowly turn the crank back to Z1. Holding the cam lobe with your finger works because there isn't significant resistance against the cam (there shouldn't be).

If you are trying to tighten the cam bolt down after final timing (which is not what it sounds like you are trying to do), you would of course have the pin in, and the cam bar locked in the sprocket to hold it in place while you tightened the bolt.

Lee

How many rocker arms have you attached to this cam? Just the #1 and #4 intakes? I ask because in your last post you make it appear that when you pull the pin, the cam spins. That can happen if you have a rocker which is on one of the lobe ramps, and not on the base circle (or delicately balanced exactly on the nose). But with ordinary cams the lift at the timing dimension is not high enough to cause trouble much trouble if you only have that one rocker attached. Despite this, it is possible to time the cam even with all the rockers in place.

But your first post makes it appear that you not only have to pull the pin but also rotate the crank for the unwanted cam movement to happen.

I don't have experience with the bolt end cams, so can't help there. Mine so far are all the big nut type, and the holder in one hand does its thing with the cam.

As a last resort, maybe if you rotate the crank until you have the cam on the timing rocker's base circle you can remove the pin without more movement, and then move the cam (or crank) so you can reinsert the pin one hole over whichever way you want to go?

Me, I find that there is enough slop in the pin system that I have to set the final timing by tightening the nut when everything is as close to right as can be. I assume this can also be done with the bolt end cams. This cam movement might make that problematic if you have no separate way of holding the cam beyond the chain to the crank.

Walt Fricke

You should only have the intake rocker for number 1 and number 4 installed. All other rockers should be removed. I turn the engine until the rocker is not depressed before I try to remove the pin. Then I advance or retard the cam as required, put the pin back in and then recheck the timing. There are lots of ways to skin the cat. Just try different ways.

-Andy

Personally I like the later engines with the PS and air pump pulleys on the other end of the cam... :D With these you just temp. bolt the pulleys on and can hold them right there with your hand.

There IS a cam holding tool that I seriously might invest in. With as many engines as I do in a year, the time savings from having to muck around with the last few thou' timing the cams would be worth it.

The tension you have on the chain/sprocket also moves the cam when you turn the pulley.

I agree!

I had to stare at it a while, but I came up with a solution. I removed the big washer and just put the bolt directly into the cam then torqued it down a bit while holding everything with the 9191. Set to Z1, pulled the pin, turned the cam with the handy dandy bolt until my number came up on the dial gauge then inserted the pin. Removed bolt from cam, installed the washer and torqued to spec.

I'll recheck everything tomorrow. Right now everything's torqued and the difference is around .03 mm. Should I live with that or try to get it closer? I don't think my pin locations would change... I'd just have to retorque them and see where they land.

Prior to removing the pin, can you just loosen the rocker to preventing the cam from rotating? Then just remove the pin, rotate the crank.

Afterward, you would have to adjust the valve clearance back again.

HI check out this it may make some sense.

http://forums.pelicanparts.com/911-engine-rebuilding-forum/309382-setting-cam-timing-bolt-snout-cams.html

regards mike

I wouldn't worry about .03mm difference.