Although the final bits and pieces of the Test fit are covered in the Test fit — Final items post, I thought fitting an upgraded servo warranted a separate entry.
The Mk 2 braking system is servo-assisted with a separate vacuum reservoir, known as a reservac. The servo is mounted through the inner wing and the vacuum reservoir under the front wing, as can be seen here. A cover fits over the servo protecting it from road debris, and a stone guard protects the reservac. The original equipment servo is a Lockheed 6 7/8″ unit.
Rather than refurbish my existing brake servo and to (hopefully) improve braking performance, I decided to upgrade to the Lockheed LR18230 servo, purchased from SNG Barratt in the UK. The LR18230 has a 4.25:1 boost ratio, which is an improvement over the original servo, which I believe to be 3:1.
Of course, it would be too easy if the replacement servo fitted without modification, but we are dealing with classic Jaguars here! The original servo has three mounting studs around the perimeter. These attach the servo to its protective cover. The new servo has three mounting studs, which are located towards the centre of the unit. Therefore the mounting arrangement needs to be modified.
I decided to add this to the test fit list rather than tackle it later when the body was completed and painted. In their excellent Jaguar Mk2 restoration project, Kriss Motors cover the approach they took in fitting the LR18230 servo to the Mk2. This was broadly the approach that the team at the Surgery followed. The Jag-lovers forum also has several threads on this subject.
The first thing to check was the fit of the reservac and servo cover under the front wing to ensure that everything was snug. Apart from a broken mounting leg on the reservac, all was OK.
Modifications are required to mount the new servo (with its different mounting stud arrangement) to the existing cover mounting holes. Kriss Motors solved this by fabricating two braces connecting the new studs to the existing pattern. We followed a similar approach.
In my installation, the servo cover needed modification to allow space for the vacuum hose connection. This modification looks good (not that anyone will see it under the wing) and does the job perfectly.
The final few items were to replace the broken leg on the reservac cover and fabricate a bracket to provide additional support for the reservac. Jaguar fitted this from chassis number 127334 (mine is 111582). The bracket fits from the top of the reservac unit to the servo cover. Thanks to Eric Kriss for highlighting this in his blog (see link above)
Finally everything was cleaned, primed and painted, ready for the day when it all goes back in the car. Here are some images of the painted servo cover.