Smooth idle: YES

I thought it had died at the lights. Only heard the car beside me. The antenna barely swings at idle, like two millimeters…

Here’s how.
I found the the engine with the intake cam a hair misaligned (too my much valve overlap) but not far from factory. Age or PO, not sure. I set the engine with the exhaust cam advanced by the width of the notch. I knew this worked and was supposed to help idle so I didn’t bother going back and getting it spot on.

It pulls well up to 130 kph, and sounds better. And it doesn’t nearly stink as much as it used to. I‘m sure there is not much of a disadvantage.

If anyone is willing to try that some day, please report. I want data.


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An entire width of the notch is significant: glad it’s running well, now.

Oh yes.
And it also runs better than most of the (few) I know so it is certainly a significant change that is worth looking at when there are no vacuum leaks and no other stone was left unturned.
If set per the factory it could be better or worse, I don’t know.

I suppose on could count “notches” and as such determine degrees per notch. Tnen, thinking or even research on the effect of advance or retard by degree would be interesting.

I dimly recall that Ford deliberately built in a lot of retard on 460 cam by the placement of the key way on the drive gear. Ran lousy. Many “fixed” that

And eccentrics have been around for decades to adjust cam timing on SBC’s .

I recall DD posting on a minor cam timing on tis engine that maskes it run better??


I’ll hafta research that: Harvey has a 460.

I wasn’t the first to come up with doing this on the XK and found at least two sources here in the forum.
Less overlap is always good for idle and a few have also tinkered for power but did not find much gain, a few percent at best (less than ten horsepower). I can live with that and with the head gasket thing and three speed I‘m not racing anyways.

It’s said that the chain can stretch altering valve timing.

People suggested that Jaguar was trying to get around EGR with the timing. At least that’s a rumor. Do I believe it, as there was a market with EGR?

Des Hammills describes testing valve timing for cases where the notch isn’t machined in the good spot, involves timing them on the harmonic balancer by hand.

Advancing the cam timing.

I’m sure I have a write-up in the archives, probably from 15-18 years ago or so