Timing chain

[magnum1978]

What is the proper deflection on a 1979 2.0 timing chain? I removed the valve cover to find a beautiful valve train free of sludge, but a chain I'm unsure  if it needs to be changed.

[datzenmike]

There is no proper deflection on the chain. When running the left side, aptly called the tension side, is tight and all or any slack gathers on the right where there is a spring loaded tensioner to keep the chain snug. There is however a check for proper cam timing and an adjustment if needed to correct.

 

Set the engine accurately to TDC compression stroke on number one cylinder. You can use the timing v on the pulley and the timing scale on the front of the block usually near the alternator. Do it carefully while turning the crankshaft in a clockwise direction up to the mark and if you over shoot, back up about a 1/4 turn and try again. To be accurate, you must set it TDC while turning clockwise to a stop. This will move all or any slack over to the slack chain side where it can be measured.

 

 

 

Now take the valve cover off and look at the cam sprocket. You may need a flash light to see properly. On the very back of the sprocket is a small V or U shaped notch. Behind it on the cam thrust plate is a small horizontal etched mark as shown below.

 

 

Thrust plate

 

 

 

Look at the relation between the notch and the etched line. As the chain stretches (or if someone has planed the head down) the sprocket (and the V or U notch appears to rotate to the left and under the etched line, even going over to the left of it. To be properly cam timed the notch must be below the line and just slightly to the right. The sprocket picture at the top is perfectly set. Some stretch is inevitable and sometimes a head has to be planed to remove any warp. To remove any induced 'stretch' the cam sprocket has three adjustments, all about 4 degrees each. In the picture the sprocket is on the number 1 setting and IF the notch was to the left you could block the chain tensioner so it cannot fall out, remove the sprocket and reset it at the number 2 position. This will move the notch about the width of the etch line farther to the right and time the cam properly. A small amount of extra chain slack won't hurt anything as it's the tensioner that keeps it tight and there is an adjustment. IF you cannot bring the cam into proper timing then the chain must be replaced. Otherwise no need.

 

All L16/18 engines are set on the number 1 cam position at the factory. All L20B engines are factory set on the number 2 cam  position so don't be surprised..

[magnum1978]

Very helpful thank you

[datzenmike]

As long as you can get the relationship of the sprocket and the mark on the thrust plate as in the picture, you're good. If you run out of adjustment then and only then would you need a new chain.

[Stoffregen Motorsports]

If this were a 10 year old engine that's never been worked on, I would advise you exactly as Mike has. The older a vehicle becomes, the greater the chances someone has molested it.

 

In this case, I would say that trusting the timing pointer to be accurate would be putting you head in the mouth of a hungry lion. Double check and verify TDC before anything.

[magnum1978]

One side has enough slop to hit the timing cover. This motor has had no maintenance EVER. It is going to be replaced. Thank you for replying.

[datzenmike]

It's impossible for the timing chain to hit the cover as it is confined and supported in place by timing guides.

 

 

All slack collects on the passenger side (right) of a running engine. The crank turns clockwise pulling down on the left (driver's side) tightly against the resistance of the cam opening the valves. Any slack collects on the right.

 

 

Below... the timing chain tensioner is a spring loaded shoe that pushes out and keeps the slack side somewhat tensioned.

 

 

 

What can happen if the tensioner is not properly blocked and allowed to pop out when removing the cam sprocket, is this...

 

 

 

One way to prevent this is...

 

 

 

 

 

 

Check that you have this, as described in post #2 above. If you do, your chain is not stretched and is good.

[magnum1978]

What if the guide isn't there?

[datzenmike]

It's possible it came loose... but if it did it can't go anywhere. Should be down inside bouncing around, not good. Can't see why it would be off unless it was rebuilt (or whatever) and was never put back on.

 

Which side? driver's or passenger?

 

Pictures?

[Stoffregen Motorsports]

I've seen broken guides before. They break at the bolt holes.

[Lockleaf]

I just pulled one out of a kae in about 9 pieces. Looks like the thing exploded, but I'm guessing it got caught by the chain and ground up.

[datzenmike]

I pulled a KA24E apart. Chain and guides looked good. Pulled oil pan off and all the plastic pieces were there. They are notorious for chewing the plastic guides unless replaced.

[Stoffregen Motorsports]

I've seen broken METAL guides before. If the gude breaks and the chain is loose, it can definitely slap against the inside of the cover.