I'm working on designs for an improved valve cover for the x300 engine 1995-1998 XJS's. It will reduce the sparking in the sparkplug wells that damage the magnesium cover. If I can get 20 of you together we can do a run of NEW valve covers that look exactly like the original. Please message me directly if interested.
Steve

 

Are you in the XJS forum because you are referring to the 4.0 valve cover?

Does it really do that? Aren't those coil plugs?

 

The 4L engine 95-98 is the same as the X300 so yes the coils break down and then spark and burn through the magnesium valve cover inside the coil/spark plug wells. It happens at around 120-180k miles. Even the original OEM coils will cause a corona inside the coil wells which causes the inside of the coil well to turn to black powder. When it get's bad enough then oil will leak into the spark plug well causing even more problems. Pull the coil packs and look at the wall of the sparkplug/coilpack well. You'll see bubbling and underneath the paint bubbles you'll find pitting and black powder of oxidised magnesium. There are no replacement valve covers in existence. Of course this also causes electronic havoc on gauges and dials and computer frizzing as you deliver high voltage to the ground plane of the car. The only valve covers out there are from wrecked vehicles and they are becoming more and more scarce. What I'm proposing is a NEW aftermarket valve cover that will reduce the corona and sparking inside the spark plug wells for longer life of coils and hopefully be a permanent fix. If I can get enough of you guys interested then I can get new valve covers for my 3 jags and also help out everyone else at the same time. If I can get at least 20 people interested we can start a run of new valve covers out of cast aluminium that will look exactly like the original but
improved.

 

What is the target cost for this and what time frame to complete the project?

 

Ron,
I do not have solid pricing yet. I have an estimate but not finalised.
However I would be looking at second quarter 2019 and am trying to keep the price around 800.
Steve

 

I ended up finding a used cover, had it cleaned up and then powder coated by someone who apparently knows their way around magnesium.

Will keep an eye on the cover over time and see if new bubbles begin to form over the years. Obviously I will have nothing to report for years...

 

I was hoping to see you had found support for the project. My valve cover looks like hell. Will see if it can be reconditioned, but may be too far gone. Odometer only shows 77,000 miles... but all the spark plug wells full of oil. Some idiot GLUED the spark plug seals onto the valve cover - not sure if those old seals will come off. Oh darn.
I thought gasket changes on a valve cover would be simple. Darn XJS seems to be a "tar baby" of an engineering design.