Many different heads were developed for the XK, with a variety of valve angles and port paths
William doesn’ t just take a modern attitude to how the heads are machined, but to the components and materials that are used.‘ We’ re now modifying valves, getting better valve seats, getting better spring seats. Everything is better.
‘ What I found is aluminium hardening is so good now that we don’ t need to be using a foreign material as they did in period. We fit aluminium valve seats and aluminium valve guides, so they swell up at the same rate as the cylinder head. Otherwise, if we fit a period specification part, a phosphor bronze part, when you have different expansion rates, you have things like valve guides dropping out. So for reliability, we’ ve gone full aluminium.
‘ That’ s something I’ m really proud of. It’ s clever stuff, but it’ s actually obvious. They’ re not complicated engines, but you’ ve got to be switched on to work them out. I’ m really pushing it because my grandfather, he designed one of the world’ s best engines in Forties draft technology. If he had the information he’ s got now, he’ d be doing exactly what we’ re doing. Well, he wouldn’ t because he’ d think we’ re mad
Six appeal: Straight-six sports car highlights
Jaguar E-Type Roadster It may already have enough attention in this issue, but we just couldn’ t create this list without mentioning the yardstick to which all sports cars – not just straight-six powered ones – are measured.
Somewhere along the line, things went a bit pear-shaped. More accurately, V-shaped. If the XK engine, and the two-seaters it powered, has taught us anything, it’ s that you don’ t need a V8, V10 or V12; a beautiful sonorous straight-six is ideal for a roadster. Here are some of the best in-line six drop-top two-seaters.
28 The Engine Rebuilder Issue 06