So i bought an 84 xj6 about 2 months ago and am loving every minute of it. I got it with 130k kilometers on the clock and since then have done many things. Aside from a full header back stainless exhaust and simple engine upgrades (filters and plugs/wires) its bone stock. I was wondering if there were any things to do to the I6 4.2 to get the power to somewhere over 250-300. I was looking through google for superchargers and from what i can tell the only thing is to custom mod in a super or turbo from another car. the space is there for it but i was wondering if there was a direct fit or specific made kit. thanks.

 

I don't think I'd recommend you do too much to that engine; it was already over-the-hill in the 70s. However, you can improve the exhaust and camshafts. IMHO blowing it will significantly reduce its life.

Some stuff on here give the flavour of possible mods. It's a UK firm and the owner worked for Jaguar engine development once.

PERFORMANCE FOR THE JAGUAR XK 4.2 ENGINE. / AJ6 Engineering

 

ya i figured there wasnt much, i was looking at getting a newer engine and building it up and throwing that in, maybe a blown mopar slant 6 or a v8 im not sure yet.

 

If your engine is solid I'd recommend a 1/4 breed conversion. This is when you install a modern and responsive 4 speed automatic with over drive and shorter rear-end ratio. Installing a 700R4 transmission with a 3:54 or 3:31 rear end would really wake up the car and make it feel much more responsive. The 700R4's short 1st gear will make the car seem much more lively from a stop. The Tall 4th gear will make highway cruise very quiet and keep the RPM's down so it will feel less busy. For best result do the trans and rear ratio together. Additionally...when your jag engine quits you'll be that much more ready to install a SBC if you choose to.