Sprocket chain Parallelisim. One's off.
 

My adventure of dry assembly reached an end today. I checked the sprocket parallellisim. The left side was .09mm off-which is ok. The right side is off -.813mm. I did the test 5 or 6 times. I had the cam sprockets switched at first. I switched them back to the way they were when I took it apart. It improved the clearance on the left bank but the right stayed nearly the same.

I experimented with taking 1 shim off the right. It got it down .5mm but aren't you supposed to have 4 shims on the right? Wouldn't it create some end play for the cam. It even has end play fore and aft on that bank. The left has none that I can feel.

So I'm asking if I keep removing shims and have only 2 left on that side, is that ok?

It wasn't assembled that way the last time. That side had been removed for a head stud job though.

What would make the parallelisim go out of tolerance like that?

Cam timing will seem like a cinch as opposed to this. I had trouble with the woodruff keys fitting in and I peeled back my thumbnail sliding on the timing sprocket (it fits over the woodruff key). On getting the keys to fit in(I had destroyed one at dissasembly) I used 600 grit wet on glass to carefully mill down the sides of the key until they fit in the keyways of the cams. They fit snugly, but I can take them in and out without boogering them up.
Ist that OK? They weren't going in otherwise.

Any help is appreciated.

The woodruff keys are a light press fit in the cam. Pressing them in and removing them indeed takes a light and patient touch. Keep your arsenal of 4 letter words well stocked.

The cam nut will take up any end play - the shims merely set sprocket depth, nothing more. 4 shims is suggested as a starting point on the right but is not a requirement. Add/remove shims as necessary to get the offset within spec. Sounds like in your case, 2 shims should do it and get you to +0.187mm.

I just re-read your post- you're doing this on dry assembly. Get down to spec and then don't worry about it!! Your gaskets aren't in yet and your final assembly hasn't been done - you've got to redo this measurement on final assembly and the number of shims used may change.

Dave,

Thanks for the encouragement. The woodruff key took a screwdriver and vise grips to get out on the left side and some tapping with a hammer on the screwdriver. Hundreds of dollars were going through my head. The right just took some light tapping. The new one fits in like you describe.

I have the cam keeper gaskets on dry. I have another 2 ready if they get ruined.

On to timing and then on to valve clearance check.

Thanks!

On the right, went down to two shims. Measures .07mm. Success.

Timed the left bank. Going for the valve clearance check next.

That's what the shims are there for - there is no set amount for each side...

-Wayne

If the woodruff key was hard to get out, are you sure it's IN all the way? I see this often enough that Ive gotten to be proficient at removing and installing the tight ones...

The top of the woodruff key should only stick out about 1-1.5mm... If it is sticking out more, it can get cocked in the slot (!) when you push the pulley on.

They are in and not cocked. They come out relatively easy now. (slight force but not enough to booger them up).

Thanks

I'm possibly a bit confused on this. The surface we can get to on the lay shaft is some distance from the surface of the fist gear and then there is the distance to the face of the more inward gear. What are those? Maybe I need to read the Wayne book again and take another look at the diagram. I thought I only saw one number.
-h

Now I'm confused?

-Wayne

He appears to be asking what the distances are from the reference end of the intermediate shaft to the chain drive gears are.

Yes, let me go look better at the parts and info. before I stir up to much trouble. Sorry for any alarm. -Henry

I need to read more carefully. There are two numbers in the Wayne book. You can't measure from the case to the gear face on the late model cars and all the cars have the same distance face to face on the intermediate shaft. I tried to get the tensioners apart today but couldn't get the bottom part out. Also I noticed that the bottom insert doesn't really come and touch the snap ring face. I'm really starting to get worried about these idler arms and tensioners. Today I had the idea to drill the idler arm shaft and pressure feed it also so that the arms won't bind. I also noticed that one of the tensioner tops looked like is was pressing on the arm in a number of different places as if it was turning during operation. That seems good. The other one looked like it had not turned at all. Curious. I'm going to email Jim and see where the Woods slug info. is and start making some.
-

Don't over-engineer the factory's solition. Just for future reference, here's what the factory did to eliminate the tensioner problem:

- Redesigned the spring loaded tensioners (later 930 style)
- Increased the bearing width on the idler arms
- Combined pressure-fed and spring loading in a single tensioner (Carrera chain tensioners).

-Wayne

Wayne,

OK, I tend to hyper focus a bit. I'm checking the clearances on the arm, polishing the shafts with 600gt. just a bit to get the slight marks out and getting the slugs....I guess clean everything up and bleed and go for it.... I plan to put in new chains and sprockets and reuse the idler sprockets. The idler sprockets roots don't look worn.

I'll see if I can not post about this for a few days... :-)
-Henry

ok, it's been a few days. I just laid out my cam sprockets to see if there was a wear pattern. There is....in both cases the chains seem to have been fed to the sprockets too far to the rear of the car causing wear on both sprockets on the front of the car side.

Here's a thought...I propose the idea that the wear on the cam chain sprockets is not substantually caused by the cam sprocket relative to the intermediate shaft...it is caused by misalignment of the idler sprocket. Yes I know the idler sprocket is supposed to self center. I think a key word in that sentence is "supposed" Remember the chain is fed to the cam by the idler not the intermediate shaft gear. All the intermediate shaft gear does is pull the chain off the cam gear. Maybe this is an analysis looking for a problem but considering all the questions and discussions about idler arms binding, and cam sprocket wear I think it is a fair discussion point to bring up. Another observation....take a look at the wear markings on the tip of the tensioner and the marks it makes on the idler arm....there is no rocket science going on there I can tell you that. It is also interesting that the position of the idler sprocket is somewhat free to move +/- 0.060 inches... in terms of cam alignment to +/-.25mm this is a mile.

-h

cam sprocket shim adjustment
 

Do you have to fully torque down the cam sprockets everytime you adjust the shims for remeasure or is very tight good enough?

Thanks

IMO - if your sprockets show wear this is a great time to replace them

I agree, at this point I don't think we know the root cause of these sprockets wearing on one side or the other. IMO - a location +/- 0.004" 1.5 feet away is not the obvious cause. That is a small angle change. I shimmed my idler arms to reduce movement while still allowing them to center. Bottom line, the sprockets wear, while you are in there replace and go another 150k miles or until you pull the engine apart again for likely some other reason.

Tight seems to work good for me, You do have + or - 0.010".

I can't think of a reason that firm hand tight with a wrench and therefore easy to undo would not be tight enough for shim selection.