Installing Timing Chain When Rebuilding Motor on Stand

[240260280z]

For the archives:

When following the FSM instructions and installing a new timing chain, this works:

0. Configuration: Head is on block with two middle cam tower head bolts at 14ft-lbs; head assembled; Cam sprocket is torqued to 100ft-lbs, Crank sprocket and Woodruff key is in place. Cam is at #1 and crank is at TDC. 71 L24 block with N47 maxima head.

1. Do not install chain guides or tensioner.

2. Drop chain through hole in front of head.

3. Wrap chain around crank sprocket with bright link next to dimple.

4. Firmly pull the chain up and wrap around cam sprocket with bright link next to #1 dimple.

FYI the timing chain guides and tensioner prevent the chain from reaching over the sprockets (if you start from the bottom or top). This tip should save you a few minutes of noodling around.

FYI#2 the photos in the Haynes manual show the timing chain tensioner with ~ 1cm of outward extension. This is incorrect.It should have 0 extension (see below). To take out the slack, adjust the top of the right side guide (above the tensioner) (see last photo below[not l24/26/28 block]). Moving this guide will pull the tensioner in. As well, ensure the lower end of the same guide is "in the shadow of the tensioner" rather than driven out into the rotating chain.

Edited May 22, 2012 by Blue

[240260280z]

PARTS:

CONFIGURATION:

CAM TIMING ALIGNMENT:

REMOVING SLACK:

[LeonV]

Nicely done!

[Reverend]

If you're ever around here, i'll buy you a sixpack for this

[cycloid]

Wish I had this info before I bent my valves!!

[240260280z]

FYI the photo thumbnails (not drawings) at the bottom of post #2 are not correct. I was unable to remove from the post however I did not enlarge them.

In this photo, you can see the timing chain is loose and the tensioner is already extended:

WRONG WRONG WRONG: More than 0mm of extension (one should not see the silver shaft of the tensioner)

WRONG WRONG WRONG: More than 0mm of extension (one should not see the silver shaft of the tensioner)

[Hardway]

So is this a case where the chain guides are not in the correct position causing the tensioner not to be able to take up the slack? Is the chain too long? I see you are driving home the fact of installing the chain first before the guides and the tensioner. Most people I can see would think to have all those items in place before installing the chain.

[240260280z]

So is this a case where the chain guides are not in the correct position causing the tensioner not to be able to take up the slack? Is the chain too long? I see you are driving home the fact of installing the chain first before the guides and the tensioner. Most people I can see would think to have all those items in place before installing the chain.

If you loosen all 6mm bolts holding two guides and tensioner then press here (see below), the slack in the tensioner will disappear.

FYI I used a socket extension as a lever to pry the top of the right (relative to driver) guide as opposed to using my finger as in the diagram. I then tightened the tensioner, the curved guide then finally the straight guide,

[240260280z]

Some pics I just took of the motor I am reassembling.

The full monty.

The 0mm tensioner slack.

Cam 1st position and bright link.

Crank up, dimple and bright link.

[GreenZZZ]

Question for you, when do you use the top sprocket 1, 2, or 3 adjustments?

When I put a new chain on some time ago the chain was pretty slack until I put it together with the chain in position "3" on the top sprocket. This was a new chain with a rebuilt E31 head. When I put it together I was thinking my head was shaved w/o appropriate shimming on the cam towers. Car ran great setup like that, but I'm no L motor expert...

[LeonV]

Question for you, when do you use the top sprocket 1, 2, or 3 adjustments?

When I put a new chain on some time ago the chain was pretty slack until I put it together with the chain in position "3" on the top sprocket. This was a new chain with a rebuilt E31 head. When I put it together I was thinking my head was shaved w/o appropriate shimming on the cam towers. Car ran great setup like that, but I'm no L motor expert...

Cam sprocket adjustments are used to correct for timing chain slack, as described in the FSM and other Z manuals. Your thinking is probably correct, if the head was shaved by not shimmed, the cam would be retarded in the 1 position. The cam is advanced by 8 degrees when in the 3 position, compared to the 1 position, which is a lot to correct for just a shaved head.

I don't know the exact diameter of the cam sprocket, but if it's assumed to be 4", the head would need to be shaved .280" in order to retard the cam by 8 degrees. You may have had a combination of a shaved head and timing chain that was out of tolerance.

[olzed]

Thats good coverage Blue, and should help many people out. Thanks

I could have used the advice a while back, but managed to sort it, using my Haynes manual.

Brian