Ok - so I am a little irritated fighting off this bronchitis but this has been on my mind for some time. What in this great universe was Jaguar thinking when they de-designed the valve cover on the XJRI6 engine? At that time management was pushing for the ultimate Jaguar driving machine, better looking than the 750 and the Merc..- the quickest 4 door sedan in it's class. Shouldn't this cat's growl be topped off with a valve cover as classy as the car? Sure, there is this plastic looking aluminum piece that says 'supercharged' and that is a big flat wow.
The earlier version of this engine has a slotted high performance style cover that someone might mistake as belonging on a Ferrari. Even a Rover cover looks better. Ok - my mini rant is over; has anyone tried using this earlier cover on our engine? Is there anyone with creativity modifying this cover?

 

Hi Richard,
I'm sorry that you don't like the AJ16 cam cover. It is made of magnesium making it lighter than the AJ6 aluminium. I doubt there are many applications of magnesium material in 1995MY cars. It was also mechanically isolated from the cylinder head to reduce radiated noise from the cam cover. I agree that the ribs on the AJ6 cover looked better but required an extra machining operation that added cost. I think people have fitted AJ6 cam covers to AJ16 cylinder heads but you would have to drill and tap extra holes into the AJ6 covers to secure the on-plug coils. Oil could escape up the threads of these holes as there are no bosses cast into the underside in the right places to allow these holes to be blind.

 

The appearance of the thing is the least of my worries. It's the corrosion issue that makes me hate it.

The old ribbed covers were OK, but I personally like the old old shiny polished look most of all.

 

I agree.

My 3.2 has started the dreaded blistering, it looks "SO SPECIAL", but fair dinkum also PLUG UGLY. It may be "cutting edge" for the year, OK, but it is a fairly lousy cast thing when you have it off and look at the internals, mainly in and around the spark plug tubes.

Much thought (and drinking) is going into what will replace it.

 

Making the cam cover out of Magnesium is the dumbest thing Jaguar could have done. Didn't Jag have any body on the engineering payroll that under stood corrosion and electrolysis. The only thing that could have been worse would have been Zinc. When you expose mag to a moist environment, as you have with conensation in the plug wells, and a magnetic field, as you have around the coils, you are absolutely guaranteed to have corrosion. Eventually all of these covers will turn to dust. When I worked for Boeing I found out that if any engineer ever specified magnesium he was immediately de badged and escorted to the front gate.

EZDriver

 

About that blistering, has anyone found a good way to clean up those scabs to make the cover look like it doesn't have Leprosy?

 

One of the fellows on XJR6.com described a lengthy process of sanding, sealing, priming, and repainting with some rather special-sounding products....well special sounding to me, at least.

I have no experience in the matter but apparently ordinary engne paint won't work on magnesium, or so that's what I led to believe

Others will chime in

Cheers
DD

 

I've sanded, sealed and repainted the cam cover on my '96 VDP and it lasts about 18 months to two years. We could each have a stash of two or three used covers and refinish as needed with regular rotation. The only solution, really, is a non magnesium cover.

 

OK, so reading all this and NOT disagreeing one bit.

I have been thinking outside the box (my normal area), and looking at my car, YES, the cover is in fact "insulated" from the rest of the engine, NO metal to metal contact.

So this in fact would reek havoc with electrolisis as I understand it.

What would be the "plus or minus" of attaching a simple earth lead from say the rear coil mount screw to a suitable earth point on the body. This would effectively "earth" the cover, and supply a path for electical stuff to dissipate????. It wont address the moisture in the holes, but I reckon that is minor in the big scheme of things here??.

I know earthing of the radiator on the V12's is a good thing for that very same reason, and that is due to the "low coolant" probe using the coolant as an earth path.

 

I've never taken the time to consider eletrolysis...it's a good point and I'try a ground (earth).

 

I actually think putting a ground connection between the cover and the engine would probably make it worse. It would act as a battery moving atoms from the cover to the engine. On boats we use zinc blocks bolted to the bronze rudder, prop and other under water bronze parts to protect them. The zinc dissappears and the bronze part is therefore protected. Magnesium is very close to zinc in this manner.

Is there another cover that is made of aluminum that will fit even if it has to be modified? The mention of the XJ6 as being such a cover. I don't know what car that is on. If these covers aren't replaced with aluminum there will be no really long term X300 cars.

 

Yep.

The "late" XJ40 which had the oil cap actually ON the cover are what is needed, but they are kinda skinny on supply.

Dont leave your bonnet/hood open if you got one, I am watching.

 

Enjoying the conversations here and hope we can find a decent solution: has anyone Powder Coated their cover?

it looks to me our coil-overs are grounded through one of the bolts attaching it to the cover and the cover is grounded to the block through the bolts attaching it to the head.

The corrosion I see is mostly all around the coil-overs. What difference would it make in performance by adapting coils set remotely that have just wire leads to the spark plugs? This would also let more air circulate around the plugs.

 

Richard,

The Corvette guys are apparently powder coating theirs, Magnesium also, with mixed success from what i can read.

I believe the coils are earthed via the 2nd wire in the plug, one is power, and the other is earth. The securing bolts are just that I reckon.

There is an increasing discussion of the coils arcing inside the chamber, which would be fatal over an extended period.

The cover is not earthed to the engine via the mounting studs, due to the rubber seal inserts in each stud hole in the cover, then the outer seal itself, and the 6 for the spark plug tubes, kinda insulates it as I understand it.

I am researching my options, but dont hold your breath, it is NOT a priority at the moment. An oil leak at the oil filter o/rings on HER V12 is significantly more urgent.