Nope, heads are all identical for 2.4, 3.4 and 3.8 Mark 2 age for age. So no physical difference at all, so it seems the choice of metallic mid/dark blue was purely a marketing exercise to visually identify quickly as a 3.8 litre block/engine, for those not into interpreting the stamped in ENGINE No prefix letters…
I would have thought smaller combustion chamber relative to bore equals higher compression, all else being equal. Maybe the dome on the 3.8 piston is relatively smaller to compensate.
It would, but the compression ratio was determined by the size of the piston dome.
My 1967 Mark 2 3.4 came off the assembly line March 31st 1967, badged a 340 and sent to the USA to be sold. The car had thick bumpers and smooth cam covers, but the dealership still had sold it as a ‘new 340 model.’ I bought the car in 1989 , entrusted it to a British mechanic living here in Southern California for a complete engine rebuild, which I knew it needed when I bought it. During the 9 weeks he spent rebuilding the engine, I sent a letter to Jaguar’s US main US facility located in New Jersey. Several weeks later, they sent me a letter telling me the car is, in actuality, a Mark 2 3.4 which came off the assembly line on March 31st, 1967. The car came with an owners manual for a Mark 2 3.4, and in the ‘transmission’ section of that manual, the photograph of the shift pattern of the ‘stick’ was a for an all synchro gearbox, which my car was fitted with. When I returned to pick up the car, I asked the mechanic why, when he had sent out the cylinder head to be rebuilt, did he not have it painted light blue as was befitting the 3.4 Mark 2 cars of that era. He replied that the cylinder head , which had numbers matching the engine which came with the car from the factory ( all other numbers matched as well),had never been painted from the outset, confirming the stories of cylinder heads on cars ‘some time in 1967’ were, in fact, fitted to cars at the factory unpainted.
Thanks for that, especially with exact dates…
I hadn’t looked into the saloon painted heads situation all that much, but as you imply, I probably agree the decision to stop painting heads was most likely across the board - saloons and E-types…
Will add to my data base…
In 1976 when I bought my 1967 E Type with an engine that had never had the head removed from new, the head was painted SILVER.
Welcome to the community!
Hi Bob, sure it was painted and not left natural aluminium?
My head had some silver or aluminium paint traces on the copper washers in the valley - definitely paint. I‘m relatively sure it wasn’t touched after 1976/77. The usual consensus seems to be they weren’t painted silver.
I wouldn’t mind hearing yours was painted too.
Mine definitely had Silver paint on it!
I’m careful with head paint. My 3.4 L 150 still has the original “Pumpkin Gold” paint. I had to have extensive work done on it due to corrosion but they were careful not to ruin the paint. $2,500 work due to the wrong coolant! USE EVANS COOL! I have in all three Jags and my MB 280C, and putting it in my Ford Lightning,
Bob
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Paul,
I hope you can get this link, I’m not a computer Wizz,
Bob
Thanks,
I AM A Jag Lover! Two XK-150 OTS one RHD 3.8 L “S” with manual OD.
The earlier one is an early 3.4 “S” It is so early that there is no “S” the doors, and since these were the first cars to use 2-1/8 brake cylinders on the front, mine has cylinders machined out of a solid block of steel. I don’t know how many came that way!