90 XJS V-12 Timing Chain Tensioner Release
 

I pulled both heads on a used engine and changed the head gaskets.

I have a reprint of the four volume XJS Service Manual. In Volume 1, section 12 for the 5.3 V-12, procedure for changing head gaskets discusses releasing the timing chain tension in order to refit the timing gears onto the cam shafts.

What it says is "Remove the rubber grommet from the front of the timing cover. Insert service tool JD50 (Release Tool) through the timing cover and release the locking catch on the timing chain tensioner."

It has been a couple of years since I last performed this procedure and can't remember whether rotating the tool CW or CCW releases the tension.

Can anyone tell me which is correct? The manual does not say, I assume that they assumed everyone would know.

I believe it is a CCW turn required but sometimes it may bind up requiring rotation or rocking in both directions.
I think it is recomended to lower tensioner slowly on catch release rather than let it snap back to bowed state.
Heads can be changed without tensioner retraction with a little more effort which l think is preferred on any engine with an ageing tensioner.

CCW did release the tension lock. I went through some containers of spare engine parts and took a couple of photos of what we were talking about.
https://cimg4.ibsrv.net/gimg/www.jag...2985ec1102.jpg
https://cimg6.ibsrv.net/gimg/www.jag...c6e2b7e369.jpg