What is the horsepower of a 4.2 XJ6 engine with 9:1 CR pistons


The Healey 4000 that I mentioned above.

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In my private opinion, my lump has the same or better value with it’s LT1 than it did with the DOHC.

My LT1 has the right torque curve for the weight of the car and the way it is driven most of the time.

I admire the XK egine and was a strong reason that I got my 83 in 01!!!

I have never understood why the XK is a long stroke engine with such a great breathe head. DOHc, straight a cross ports, hemi shape combuston chamber? All to breathe / Hiogh RPm potential. Stroke not so good at high RPM??

DOHC with three dual throat Webers. Nw we are talking!!!


XK engine was designed with UK taxation laws in mind, a rule that penalised engines with a large bore. Legend has it that the prototype engine of 3.2 litres (83 x 98mm ) lacked low end torque, so was stroked to 106, where it remained for the rest of its days, apart from the 2.4, 2.8 and racing versions.

Aye, now i recall reading of the old tax laws. bore being the basis.


The 205 bhp DIN rating taken at the flywheel for the SIII saloon was the most powerful XK engine built for a road going saloon. The figure of 245 and 265bhp are widely taken as being small horses rather than Clydesdales. Closer to 210 and 200bhp arguably.