how to tighten cam nut without moving cam

[millhaus]

I am having problems tightening the cam nut without moving the cam. I have the crows foot and cam tool but it seems impossible to tighten to 150N without the dial guage moving.

Any good suggestions? Is it possible to torque the large nut, then use the cam tool to rotate the cam back to the correct dial indicator setting? Assuming it only moves 0.10mm out of position while torquing the nut?

[lucittm]

It is the definition of trial and error.

Mark

[jpnovak]

It should not matter if the cam moves as long as the pin is in place. Yes, your dial indicator will change as you tighten the cam nut but you should rotate the engine 2X to take the reading again.

I set the crank to TDC. Then rotate the cam until you meet your timing spec for lift.. Then insert the pin and finally tighten the cam. Rotate the engine and recheck your cam timing. If your reading is off, just loosen, change the timing and repeat the process. Once you have repeatable timing measurements you can torque to spec.

[cstreit]

You can't. But you do figure out about how much it moves, and then set the timing off so that when you tighten it and it moves, it ends up where you want it.

[snbush67]

You have to get lucky, its going to move no matter what. You wont know if you got it right until you check it.

[Walt Fricke]

The pin won't keep it where you want it with any precision. You can get maybe 0.015" change in overlap with the slop in the pin.

I usually find that if I can get it nice and snug at where I want it (which is all I do when timing initially, then rotate to check), it moves little or not at all when I apply the final torque. It is a lot easier to hold things constant when snugging than with the large final torque.

You do get from the other comments that it isn't the needle moving when you tighten it that is the issue, because you are apt to be moving the crank as well as the cam some. It is that final 720 degree crank rotation which tells the story.

[ChrisBennet]

Like Walt said, the pin doesn't locate the sprocket with precision.

As we say in the software world, "That's not a bug, it's a feature."
Think of the holes as very short "slots" that allow you to fine tune your cam timing.

Also; you can't just turn the motor 720 degrees, look at the dial indicator and call it a day. You need to take multiple readings to see how repeatable you readings are and take an average.

[88911coupe]

What Walt and Chris just said is what seemed to work for me when I did this PITA project last summer. Don't want to do that again anytime soon. Of all the rebuild "sections" cam timing gave me the most frustration by far since I don't think I every really got mentally comfortable with what I was doing. I followed directions to the letter and my car runs perfectly now (2,000 miles post rebuild...fingers crossed) so I must have gotten it pretty close. I really admire those on this board who take the time to help the rest of us not destroy these enginerring marvels.

[notmytarga]

I spent a lot of time at this step in the rebuild assembly. My goal was to achieve a fixed and matched overlap setting on both cams. I figured that the cam fixation hardware, spec books as well as Pelican wisdom would help me. The responses in this thread provide the variety of opinion and emphasis I saw when I worked through this step.

The spec book or Wayne's rebuild book provides a range for the cam valve overlap. I wanted dead center (or maybe a bit advanced) within that range on both sides and spent a week trying to achieve it.

What I found was: The pin does not help to fix the setting at an exact value. It really just keeps the overlap in the range - if set right. So I spent my next few days trying to get a pin setting which stayed in the range. This itself is not even easy, and requires moving the chain on the sprocket etc.

I ended up with bilateral dial indicators to prove to myself it was all good, on both sides before buttoning up. Nearly matched overlaps, but the pin keeps the cam from rotating out of range if the cam nut lets it slip.

Good luck.