Why it came out again
The engine had been overhauled in 2008 at 76,300 miles. It never settled.
After the rebuild was completed it felt very tight and ran hot, taking around 5,000 miles to bed in, but still ran typically 10 degrees higher than its specified normal running temp of 75 to 80C
By 2018 and 92,500 miles it had developed rattles at various temperatures, a heavier bottom-end noise once hot, and an oil leak at the back of the block.
Whilst it always had sufficient torque, compared to my XK120 roadster engine, it felt harsh and unbalanced at anything over say 3,500RPM.
What he wanted the second time
What I'm looking to achieve this time: The best possible rebuilt bottom end running very smoothly up to say 5,500RPM. Full cylinder head rebuild incorporating the best available components.
The specification came from Dan Mooney of Classic Jaguar in Austin, Texas — a friend who had once been his next-door neighbour in Durham.
What changed from standard
| Component | Specification |
|---|---|
| Head | Ported and polished to stage two |
| Tappets | Rob Beere chilled cast 1.4 inch into reamed guides |
| Valves | Stainless, inlet increased to 1⅞ inches |
| Valve seats | Lead-free hardened, 45/30 profile |
| Guides | Silicon bronze, close tolerance |
| Head gasket | Cometic multi-layer composite, ARP head studs |
| Pistons | Ross forged, 10:1 compression, +30 thou |
| Rings | Total Seal |
| Con rods | Corrillo specification |
| Chain tensioner | SNGB uprated hydraulic |
| Timing chains | Reynolds endless |
| Crankshaft | Ground to −10 thou mains and big ends |
| Damper | Harmonic fluid type |
| Flywheel | TTV lightweight steel, 132 tooth, 5 kg |
| Clutch | AP 9.5 inch diaphragm, E-type |
| Balancing | Rods and pistons matched to within 2 g; all reciprocating parts balanced individually and together |
The coin
It was easily possible to balance a coin on edge on a Rolls Royce engine so I tried it on my superbly balanced XK 3.4 at tick-over (800 RPM). As you can see — absolutely no problem.
Fuel
The original steel tank was rusting from the inside out, and an aluminium replacement cost about the same as the internal coatings he was considering. The carburettors needed only bushes, spindles and seals — but the copper floats were replaced with nitrophyl, because E10 ethanol dissolves the soldered joints on the originals.
The XK140 was never given a separate fuel filter, relying on mesh in the carburettor banjo fasteners. A glass-bowl filter now sits in the offside battery box, reachable by removing the front cover, with a pressure adjuster set to 2 to 2.5 psi.
Transmission
The original Moss box with overdrive was worn and noisy, and some parts were then unobtainable. It was replaced with a Tremec T5 WC five-speed — the gearbox from Mustangs and Cosworth Fords, so barely stressed here — whose rear extension puts the lever in exactly the original place. Fifth at 0.82 is close to the Laycock overdrive's 0.778.
The differential went from 4.09 to 3.54 at the same time, which drops 70 mph from 2,800 rpm to 2,500.
Photographs
- 11 January 2018
- 27 March 2018
- 29 March 2018
- 16 May 2018
- 16 May 2018
- 27 May 2018
- 28 August 2018
- 2 October 2018
- 22 October 2018
- 24 March 2020
- 31 October 2025