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Tightening the Upper Timing Chains, 4.2L Engine

Tightening the Upper Timing Chains, 4.2L Engine

Carlos Robert

Bruce asks:
My humble request is that if someone has a copy of a detailed (or even semi-detailed) explanation of this procedure or a like to such a place, will they please send it to me. I know some do it with needlenose pliers. I will probably try it that way first and then pester my machinist friend to finish the tool he started using the Haynes drawing. The pins ARE fixed, right?

From Carlos Robert:

Chain tightening procedure. (How I did it, with long nose pliers two weeks ago on a 1982 XJ6 S3.)

1. Start with a fully warm engine, that way you don't need to worry about over tightness due to different expansion rates.

2. Get a small flashlight and look inside while someone cranks the engine (ignition disconnected) for broken links, etc. This is not a substitute for a full chain check, but at least you don't need to get the cam covers off.

3. Check for slack on the right hand (lagging or return) side of the chain (it will be your left side facing the engine, standing at the left front fender (wing). Use a thin wire hook (cloth hanger works fine) to check the chain slack. Since gravity (chain weight) will pull the chain down, the wire hook allows to pull the chain up to check its tightness.

4. Just slack the nut. You don't want it to fall inside the engine.

5. Press locking plunger, I was able to use my finger. Turn the pliers counterclockwise fairly tight (I am right handed, and used my left hand and a 6" pliers). Release plunger and slightly turn clockwise to engage back the locking plunger. Tight locking nut.

7. Check chain slack as described above. Depending on the source, the slack should be about almost nothing to 3/8" cold. Since there is a possibility that camshafts could be damaged if the chain is over tightened I tightened mine to about 1/4" (warm). This was a trial and error. The first time it was not enough and the rattling continued.

6. Start the engine and look again. No, it will not spit oil, unless the engine is over-revved. Let it idle for a couple of minutes after it reaches 90C again. Turn off engine and check the slack one final time.

7. Get plenty of gaskets and plan to do this operation regularly. It won't do any harm and will help eradicate the belief that the clanging/rattling noise is "the way Jaguars should sound." This was the explanation the PO's mechanic gave him about this noise.


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