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dash16 · Joined: 22 Aug 2007 Posts: 255 Location: Cali Cali

before you hit any valves?

I turned a tooth clockwise on accident but turned it right back to TDC alignment mark immediately.

Almost had a heart attack

_________________
1987 Porsche 924S Black/Black. 5-spd.
Options: AFX C79 261 398 423 650 651 657

1987 Mercedes 190E 2.3-16 Cosworth Pearl Black/Black. 5-spd.

STUTTGART PREVAILS

Slam · Posted: Tue Jun 30, 2009 8:12 am Post subject:

One tooth is okay. If you're turning by hand you'll feel when the valves connect with the pistons. Be very gentle and you'll be fine.
_________________
'88 944 Auto - may or may not resurrect

edredas · Joined: 09 Dec 2004 Posts: 861 Location: Charlotte, NC

I wouldn't worry if it only moved the cam one tooth. You would need to move it two teeth or more to risk any damage. When installing the belt you'll either have to rotate the crank counter-clockwise 10 degrees or the cam 1.5 teeth clockwise to get the slack out anyways.
_________________
'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver

Slam · Posted: Tue Jun 30, 2009 8:31 am Post subject:

Ummm... with the crank locked and the cam at TDC, the timing belt will slip on and any slack can be taken up by the tensioner as it's rotated to tension the belt at least to the point you can use the twist method to make sure it won't slip off during proper tensioning.
_________________
'88 944 Auto - may or may not resurrect

edredas · Joined: 09 Dec 2004 Posts: 861 Location: Charlotte, NC

I think you're confusing the belt tensioning method with slack removal, which is what I was reffering to. Slack removal can be done different ways but, I do this by first locking the flywheel at TDC. I then rotate the cam 1.5 teeth clockwise, then with the belt installed, I rotate the cam back into position. This removes the most of the slack between the cam and crank. If you skip this step, there will be too much slack between the two. This will result in the timing being off when tensioned.
_________________
'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver

Slam · Posted: Wed Jul 01, 2009 1:59 am Post subject:

Righto.

_________________
'88 944 Auto - may or may not resurrect

dash16 · Joined: 22 Aug 2007 Posts: 255 Location: Cali Cali

edredas · Joined: 09 Dec 2004 Posts: 861 Location: Charlotte, NC

No matter how tight you try to pull the belt by hand you're going to have slack. How you choose to get rid of that slack is up to you. Also, the teeth on the belt isn't going to tell you anything either. These belts stretch and 41 on your old belt might be 39 on a new one.
_________________
'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver

Slam · Posted: Tue Jul 07, 2009 8:37 am Post subject:

Better go to www.clarks-garage.com and read up on doing the belts... Also check out www.arnnworx.com (IIRC).
_________________
'88 944 Auto - may or may not resurrect

dash16 · Joined: 22 Aug 2007 Posts: 255 Location: Cali Cali

edredas · Joined: 09 Dec 2004 Posts: 861 Location: Charlotte, NC

Yes, the tooth count will always remain the same between two points on a belt; (assuming they don't slip.) However, since rubber belts stretch, the distance traveled between those points increase.

Let's say we have an engine here with the cam in time. Assuming we're good to go, we count the teeth on the belt.... which is 41.

However, we notice the crank is not at TDC ...so, did the belt slip?

No, it just stretched.

Now, we'll remove the old belt and set the crank at TDC. With the new belt on, we soon realize that 41 teeth is too tight.

This is because when the old belt was installed it was set at 42... had you rocked the crank back to TDC with the old belt on you would have counted the correct number.

While, you're certainly welcome to try this method ...don't expect it to work.
_________________
'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver

Slam · Posted: Wed Jul 08, 2009 7:31 am Post subject:

If the crank and cam marks both show TDC, the tooth count becomes academic - it'll still serve as a safety check though. Put the long run of the belt on first, then the water pump run, and then slide the tensioner in. Rotate the tensioner to take up the slack, then check tension by twisting the long run of the belt with your thumb and forefinger. If you can just turn the belt 90 degrees then you'll be able to turn the engine by hand and not have the belt slip a tooth. Now you can start tensioning proper.

Have fun!
_________________
'88 944 Auto - may or may not resurrect

dash16 · Joined: 22 Aug 2007 Posts: 255 Location: Cali Cali

edredas, thanks so much for the input so far. your take on this topic has definitely been helpful

So I finally reached the timing belt installation phase today.

What I did was make two mark on the new belt to count 41 teeth to see if it'll line up right. Well, I did have to turn the cam clockwise about 3/4 of a tooth to line up the two marks i made on the new belt. I was able to turn the cam back to TDC, more biased towards the clockwise direction than before, after it lined up.

Judging from this, I am concluding the the old belt did stretch slightly but the teeth count point to point should remain the same.

Now, does anyone know how the belt should mesh with the sprockets from side to side? What I mean is that the belt and the sprockets are not the same width while the spring roller has an inside lip, the crank and WP pulley have an outside lip, and the cam sprocket has no lip.
_________________
1987 Porsche 924S Black/Black. 5-spd.
Options: AFX C79 261 398 423 650 651 657

1987 Mercedes 190E 2.3-16 Cosworth Pearl Black/Black. 5-spd.

STUTTGART PREVAILS

edredas · Joined: 09 Dec 2004 Posts: 861 Location: Charlotte, NC

No problem, I'm always glad to help when I can...

The slight bias towards the clockwise direction shouldn't matter. Most of the slack you need is probably just stuck between the tensioner and the crank pully... after the belt is adjusted it should evenly distribute the tension through-out the belt and fix the problem.

All that really matters at this point is that when you turn the crank to rotate the engine for the first time, the cam immediately follows. Any, degrees that crank turns without the cam, will be degrees that the timing is off...

Ok, it sounds to me like you got it, so I promise not to preach any more lol... you just wouldn't believe how many 944's I've seen two teeth off time because the belt was improperly installed...

Anyway, to answer your question... with belt installed, it should be perfectly flush with the outside (towards you) cam pully and laser straight all around from there.

Hope this helps/good luck.
_________________
'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver

dash16 · Joined: 22 Aug 2007 Posts: 255 Location: Cali Cali

so the OT mark, the flywheel, and cam all line up PERFECTLY.

I shouldn't need the timing belt to be perfectly flush with the cam gear towards me if its somewhere towards the middle and doesn't ride up on any of the sprocket lips right?
_________________
1987 Porsche 924S Black/Black. 5-spd.
Options: AFX C79 261 398 423 650 651 657

1987 Mercedes 190E 2.3-16 Cosworth Pearl Black/Black. 5-spd.

STUTTGART PREVAILS