Intake/exhaust cam relation/timing, chain marks
 

Lined up chain marks perfectly with the marks on cams, peak of the markings lined up with middle of chain links. After rotating the cams those marks don't line up anymore, instead of the cam markings lining up with the middle of the link, they line up with the end of the links. Is this just stretch? Or does the tensioner correct this when running?

Matt, this is confusing, can you post a picture? The marks and the sprockets are both part of the same camshaft casting, nothing to change there.

The purpose of the marks is to get the two cams in sync-- just be sure that any slack in the chain is on the tensioner side.

It doesn't matter as long as the cams are in correct alignment to each other. Use (a copy of) the factory tools to get the cams aligned. Once the engine is running the tensioner takes out any slack.

Well you know how you have to line up the copper colored chain links with the markings on the cams, to get them synchronized? Mine are off after rotating the cams a couple times. The cams do move erratically, so could that be throwing the chain off a tooth.

Wondering if that is due to lack of oil pressure in the cam chain tensioner?
You did start and stop at 0 TDC, right, (# 1 compression stroke)?

Edit: are they still 7(?) links cam mark to cam mark apart, I've been replacing all w/ the "racing" grade chains and they don't have the colored links, so I can't really say for sure if they should re-align after rotation.

Dave

After thinking about it, i don't think it's crucial that the colored links are centered with the cast cam marks. I wasn't timing the motor officially because i don't have the tool for it yet. Just turning the cams to see what happens, motor is on 45 after TDC and cams turn freely as ever. I don't think it's possible for the chain to jump teeth unless the chain is severely stretched, there wasn't enough slack in my chains 5-8 chain to realign it. It pissed me off because i had to do all this disassembly on 5-8 to take the intake cam out to reposition the chain links. I think the colored links are just there to provide a measurement/baseline for how much the chain has stretched over time.

On 1-4 the marks don't line up the way i had them before, but the relation hasn't changed because the marks on the cam are still synchronized perfectly with each other, ie they both point exactly the same way whenever, so am i good to put the covers back on?

Matt, check pg. 15-127 of the WSM (portion below), this shows the proper relationship between the two cams. You don't care about absolute timing at this point, that comes later when it is time to string the belt. All you care about right now is that the intake and exhaust cams are in sync, because that is not adjustable-- it is determined by how the chain goes onto the sprockets.

And yes, you are correct, the colored links are just there for the initial reference, they will not line up after you rotate the cams. And I don't think the chain can skip teeth, even with no oil pressure on the chain tensioners.

So check the cam marks, make sure the cam lobes and lifters are well lubed (e.g. ) and button it up.

Matt, note that it can be very difficult to get the cam indexing correct if the engine is still in the car. You can't do it by eye alone reliably. You have to make some (paint) marks on the gear teeth. I assume you've done this. Make sure you have 5 and 2 halves (or 6 complete) chain links between the marks on the gears as shown in the page Jim posted above.

Concur. The number of links in the chain would need to be a multiple of the number of teeth on the gear.

Nope. It can't skip. (Assuming the obvious issues are not issues: that the chain is in one piece, hasn't stretched by an inch or two and is from a 32v 928. :))

Ok perfect! Engine is out. Cams are lined up bang on. Just wasn't sure about if the chain skipped with the cams bucking about as they do. But one thing i'm confused about is how the hell do you hold the cams lined up with the marks on the backing plates?

Until the belt is on you can't keep the cams from jumping.

Use a big wrench (30mm IIRC) on the hex-shaped washer on the right (driver-side) belt gear to hold it in place while you string the belt over it. Get the belt good and tight from the crank gear to the right gear. Then, keeping the right gear from jumping with the wrench, grab the belt and string it under the water pump pulley over to the left (passenger-side). At that point, hold the belt tight with one hand, and with your other hand move the wrench to the right gear. Use the wrench to rotate the right gear into place and then string the belt.

I will usually put a small c-clamp on the left side (not very tight) to keep the belt from skipping teeth on the gear just in case I lose hold on something.

One thing to note is that I string the belt after the tensioner is installed. So, getting the belt on the right side gear is a 'wiggle' operation. If you string the belt without the tensioner you'll possibly need a clamp on both gears to keep the belt from skipping as you fit the tensioner.

It can be frustrating the first time. You'll probably end up doing the stringing operation a couple of times before you get it right with all the marks lined up.

(Y) Thanks man!

chain rotation is not 1:1 with cam pair rotation. that's why there's a tensioner, you have more chain than the engaged cam teeth and the 2 spans between them. as long as the relationship between the cams stays the same, the chain doesn't matter.

i remember when we changed cam timing adjusters on a VW W8 engine (3 chains, no t-belt), we had to turn the engine over like 50+ times to get all the brass links to line up again.

http://2.bp.blogspot.com/-6HspqRZtC2...hain-W8-sm.jpg

That's nuts!

I did this plus looked at how the factory alignment tool showed them to be lined up (just looked as I didn't have one). Everything went perfect.

So if i set the timing roughly, ie just line up the gears and marks by eye, is that ok? How many degrees of cam rotation leeway is there before valve contact.