Worn Cam lobes?

1988 V12 with about 50k miles. Car is totally tuned with new ignition/fuel system, and timing is spot on.

It idles decently, but I only get 16 inHg at idle. The vacuum gauge needle vibrates super fast right on 16, but evens out as I give it more rpm. Reading about this symptom, it states this is due to bad valve stem seals, or worn cam lobes. The car burns no oil at all.

This car had been sitting for 7 years when I bought it last year, and ran terribly rich before I had ignition and ECU fixed. I have been unable to give it an Italian tune up yet.

Only one sure way to tell…:wink:

Pull the head, or go for a drive?

Pull the cam covers.

No chance of sneaking a cheap little camera in the oil filler? Prob not but they all need cam cover gaskets by now anyway.

Worn cam lobes is not a common malady on the Jaguar V12. My parents’ 1972 Volvo had one lobe wear down to the base circle – valve didn’t move at all – while the other 7 were fine, a clear indication of a manufacturing defect. But I don’t remember anyone reporting anything of that ilk on the V12.

What is a relatively common malady on the V12, I believe, is sticky tappets. Oil varnish builds up in there, and then the valves hang open briefly. Sometimes causes nasty backfires through the intakes. The fix is better oil, notably synthetic, giving it time (a few months) to dissolve away the varnish.

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If they are made anything like the XK camshafts; they bash the tappet guides to pieces and barely wear over 100 k miles…

With my XK I suspected about everything for the bad idle but in the end it was the cam timing and a few other bits and bobs. Have you done a long trip with good oil already?

Nope, only city driving under 40 mph. I’ve sunk a few $1000 into getting her restored from non-running over the last year. By spring, I’ll have that paid off and will buy new tires (current ones are from 1999). I’m forcing myself to pay off the debt before more big ticket items.

Then I can take her for a proper run.

I’m hoping a good Italian tune-up, and time with proper oil changes, will help. It’s a low mileage engine, so I hope internals are still good…