sprocket alignment - cam drags

[jamesf]

Hi - after I did the sprocket alignment test (this checks out :>)), I thought I would check (again) to see if the cam would turn freely after tightening the 46mm nut.

The left cam binds slighty - or drags - in the same place in the revolution . The cams turn freely once the torque is reduced on the 46mm nut.

The only thing I can think of is that the end of the cam is binding against the "thrust plate" ... is this an issue- it is very slight but noticable.

...James

[Walt Fricke]

James

I'd take the cam out. Hope you haven't installed more than one rocker shaft, so it should be easy. You have the shims set, so you probably won't have to go through that again.

I assume you have a 2.0-3.0 engine.

Sounds like something is out of whack between the chain wheel (lay it on a piece of glass to see if it is flat), the small wheel behind it (you could check that also, but I actually can't imagine either of those pieces giving you trouble), the shims (do you have the thick thrust washer's bevel point the right way - not that I know if that would make a difference, and I can't recall which is the right way, but the bevel gives a little more clearance so I think it points in at the cam), and is the aluminum round holder - the 3x6mm bolt jobber - in correctly, bolts tight and the piece drawn in evenly all the way, with the red rubber O ring where it belongs and the gasket OK?

Wild guess - something is cocked in this assembly so an otherwise out of harm's way high point is hitting some other high area.

If nothing looks out of sorts after you disassemble (and pull the cam out for a closer look), you might consider where you could apply some machinist blue to the most suspicious places, reassemble, tighten, rotate a couple of times past the hard spot (noting what orientation the cam is in at the hard spot to see if that helps the diagnosis), and pull apart to see if that helps you spot where something is rubbing something else.

Since this should not happen, I'd not be inclined to just cross my fingers and forge on.

I've had a little cam binding, but that was right away, not as a result of tightening the big nut - it was as part of the head/cam carrier torqueing process.

I don't know if I have ever torqued the big nut very tightly before timing the cam, at which point the turning is done with the crank, where you are getting roughly 2X torque multiplication at the cam, so a slight bind might go unnoticed.

There is a certain amount of end play in the cam system. Does it matter if you are pushing the cam in when turning past the hard spot? Or pushing it out at that point? Still, I can't think what might hit what inside the cam carrier itself that would change unless a screwdriver fell unnoticed into the cam carrier or something.

My thoughts, anyway. Maybe someone has had this exact problem and can do more than speculate as to why.

Walt Fricke

[jamesf]

Thanks for the reply ... took the cam out ... still at the cam sprocket alignment step so this was easy ... cleaned the cam journals cam etc. Still getting a bit of drag, but can turn the cam through 360 degrees etc by hand ... cam turns freely without the 43mm nut etc. so do not think that the cam is bent or that the cam carrier is mistorqued ... may just proceed as is :>( ...
.... James

[cgarr]

Did you have the cam checked for cracks? I have seen them snap at the nut..

[rlane]

did you use a new "key" in there/ When I removed mine I left a little burr on the key which "cocked" the sprocket....

[shbop]

Did you pull the spray bars? Did you use an aluminum plug, or tap and use a pipe plug? Is the pipe plug completely flush with the cam housing?

[jamesf]

Thanks for the replies ... loosened the cylinders and cam carrier and retorqued ... still very tight after torquing the 43mm nut ... will pull the cam this looked at re: machine shop ... seems odd that the cam turns freely without the nut, spacers etc. Does not looked cracked by the threads etc. ... if cam checks out ... will remove cam carrier and try again ... i'm stumped though!

[Walt Fricke]

James

Your description of the problem leads one to believe that there is a high point on some part of the cam or inner cam sprocket, and a high point on some part of the non-rotating system that holds the cam in place, so that when turned the two come into contact and produce a tight spot in the rotation.

Since this only happens when the nut is tightened, it pretty much has to be found in the thrust holding system: the aluminum plate, the washers, and the bits of the cam and gear that are on either side. One of these things is at an angle to what it should be, so that an otherwise innocent irregularity bumps into it.

Short of a crack allowing the cam to distort with the nut tight, I don't see how the cam can rotate irregularily. But you can test this - with the retaining hardware all removed, rotate the cam by hand. First while pushing it all the way in so its far end rests against the cover plug on the far end of the cam carrier. Then in small steps (but full rotations) as you pull the cam back toward you until it is maybe a half inch from where it started. That will more than cover all the places it can be with everything attached and tight, and should discount some odd gouge in the carrier's insides allowing a lobe to catch it or something like that when tightening the nut moves the cam a little bit axially.

Also, swap the cams side to side and tighten the nuts. If the tightness does not follow the cam, it isn't the cam.

Which would mean it has to be in a fairly small number of components.

You can try swapping all of those also. You could do that when returning the cams to their proper sides, since all the other components can go on either side.

Both Richard and Jon have suggested ways that a component might not end up perfectly perpendicular to the axis of the cam. Richard's Woodruf key theory would have the inner chain wheel piece cocked, and some part of that could stick out just a bit more than the other parts.

Jon is wondering if the surface of the cam carrier that the round aluminum piece fits against (with the triangular gasket in between) doesn't have a lump in it. He wonders it this happened when an aluminum plug was reinstalled or a substitute put in. My bet is you didn't pull the spray bar, but something else might be interfering with a flush fit, which would cause that piece to be cocked.

Another notion: remove the three 6mm bolts, and reinstall them without washers. This will get them just that much farther away from hitting (rubbing against, really) anything than they were. If this "solves" it, you still have work to do, but you will know where things are hitting.

Just FOurY, how many thin shims do you have on that side?

You'll solve this eventually, frustrating as it may seem. I once ignored what felt like a little tightness in a cam while setting the timing. Damn thing froze about two seconds after the engine started. I had to remove the cover plate at the far end of the cam to drive it out. It seized so tightly that the little locating pin sheared off all of the "spokes" on the inner wheel that the pin fits between. All those cam bearings still had their nice coat of red Torco assembly lube when I took things apart. Never did figure out why that happened or what I did wrong other than not doing what you are doing - not moving ahead if something did not feel completely right.

Walt Fricke

[jamesf]

Walt -
Had a machinist friend over last night ... the gasket behind the aluminum cover was quite distorted, the cover was not quite flat and the cam was riding some high spots on the cover. The gasket was becoming more and more distorted as I removed and installed it.

Machinist thinks that the cam could also be slightly out on the mating side of the cover, but is probably normal. Could see very slight contact on the cover.
The contact is very slight now when torqued down to about 110 pounds, and should be OK (can turn by hand easily through this point). Will try with brand new gaskets etc. Does'nt really bind at all when torqued to 75 pounds (I think this was the original torque for 1970 2.2) so part of the issue is torquing to the new increased specification.

Machinist also recommended setting the covers on a piece of glass with emery cloth and flat sanding the back of the cover to remove any high spots etc.
Thanks again Walt ... much appreciated!
...James

[rlane]

James, glad you found this. I had trouble getting that Oring and gasket nice and situated myself. I had a tip to use Dow 111 Silicone as a lube there...could bnever found it but Advance and other auto parts places carry Syl-Glide...which has Dow111 as a component and is heat tlerant to about 500 degrees. Everything slid in nicely with it