Mods and Consequences
Jaguar Mk1
The Jaguar Mk2 is such a headline-grabber that its predecessor is frequently overlooked. Yet the 2.4 and 3.4 saloons, retrospectively known as the MkI, offer much of the charm of their successors but at lower prices. Also, because the MkI is usefully lighter than the Mk2 (typically by around 100kg), it’s more agile and in 2.4-litre form can exceed 100mph, whereas the later model can’t.
However, the transformation from MkI to Mk2 brought several significant mechanical upgrades, including more powerful engines, optional power steering and (from 1965) an improved transmission from a Moss to a Jaguar unit. The Mk2’s rear axle (and hence its rear track) is also two inches wider and the front suspension is unique to the MkI with its own uprights, suspension pans and top wishbone arms.
The MkI feels unsurprisingly vintage to drive, which is why for some owners it’s worth incorporating a few upgrades if you’re keen to use your Jag regularly, or take it long-distance touring. The first MkIs came with a 2.4-litre engine, with a 3.4-litre unit available from 1957. Cars with the bigger engine are much faster than those with the 2.4-litre unit but with disc brakes not fitted until 1958, early 3.4s can be hair-raising to drive if you use the available performance to the full.
Upgrades, then, are desirable; Zeus offers upgraded calipers from around £450 per axle set and you can also fit a ventilated disc set-up for around £700. Just bear in mind that if your early MkI has drums, converting to discs is a big job, but essential – which is why pretty much all MkIs now have them.
It’s possible to create a complete animal of a MkI, with a 4.2-litre XK engine running on triple Webers, but to do so you’ll have to replace all of the running gear to cope – and the engine bay and transmission tunnel will have to be reshaped to allow everything to fit. Even switching from the original 1.75-inch carbs to 2-inch items is more fraught than you might think because of limited space under the bonnet, so you need to see what has been tried before and what hurdles are you’ll need to overcome before starting out; there’s loads you can do, but also plenty of things that are not as simple as you might think.