Head Studs
 

Unfortunately I had a head gasket failure, and this time around I was interested to use head studs instead of the TTY ones from Jaguar. As I have another main ride now, there is was no pressure anymore to move fast, so I took my time here.

Without naming, there is one in the UK that sells ARP ones for way above 1.000 euros, so needless to say that wasn’t an option.

After some searching I came across a set that would fit the AJV8 engines from Raceware, and I was pretty impressed on what I read on the product, and the price was good ($470).

They were very responsive and provide comprehensive answers on my questions, so am very pleased so far.

The turnaround was quick, and I have just installed the studs/heads, but it will take some weeks before my car is on the street again, but will certainly give more feedback.

For the record, I have no affiliation or what so ever, am just very pleased with a good product at a good price.

Avos.

Did you have to pull the engine to replace the head gaskets? My understanding was that with studs, one can't get the heads on or off in the engine compartment.

Good point that was one of the reasons I was never interested in studs, as I though you couldn't (de-) install the studs with the engine in situ.

Raceware has an install tool, in simple terms it’s a long nut that on one side you turn on the head stud, and there is a bolt with counter thread on the other side of the long nut. With this you can install and re-tract them, and that’s how I’ve done it with the engine in situ.

One note though for the XKR, for 1 bolt the tool is to long (the one next to the suspension housing), they could make a smaller tool if more would be interested. You can also make this tool yourself, but make sure you use an original nut on the end that goes on the stud (for example press that one in) to avoid any damage to the stud thread with an own threaded part, as its imperative to keep the smooth surface of the threads for torque accuracy. Also I had to put the bolt already in the head when placing the head, as there wasn't enough room to put it even in.

With the smaller pitch, very smooth threads and some oil (Raceware shows what oils can be used and what not) you must torque them to max 60nm.

Did you find obvious reason for the gasket failure - Head lift under the high boost - stock bolts were unable to keep the heads down? 92mm bore makes gasket very narrow between the bores ( 5mm vs stock 11mm ) - anything to do with the failure?

It was due to neglect on my side. On 4.0 XKRs there is a plastic flow control unit (for the internal heater coolant), and that plastic part was broken. I have mistreated that one over time (remember 460.000 km, and lots of install/de-install actions), and it was already leaking for some time though I didn't worry to much as I have pressure less evans coolant system. Unfortunately it openend up and caused an overheat due to much coolant loss.

The risk of head lift might be there at higher power/boost levels, but with my street driving I have not yet experienced that part. Lets say if you do go wild in power levels, and you have the opportunity to place new bolts, I would go for these Raceware ones for the reasons mentioned, I would have done earlier if I had found this set then.

The leak was at the rear cylinder, RH side at the back, and when looking at it closely, it does look as a weaker point compared to the rest (so less block material there), so it is probably one of the more common places.