What I’d like to do, if possible is R&R my 1974 XJ12lL’s engine due to a badly leaking rear main seal with an available Series III engine that doesn’t have an operable fuel injection system. Does anyone out there know if the carburetors and intakes off my Series II can be bolted onto those HE heads?

 

Bolted ON, yes.

Work properly, I doubt it with the 11.5:1 comp ratio of the HE in your market.

Your old engine is 9:1.

Some here have tried this (we got 12.5:1 on the HE), and went back to Infection.

I mentioned in your other thread, is it the seal 100%?. I have had them weep, but not leak as badly as you are mentioning.

There is an oil gallery plug, behind the flex plat, just aft of the oil filter housing, that was a leak concern on the early engines that I remember?. Never had one leak, just remember discussions, and notations about that when I was with Jaguar.

 

I can see that you have a lot of experience with these cars, and thank you for documenting it for us enthusiast. I’m old school, and like tinkering with those carbs. On my current bike, a 1984 BMW R100rt I have twin carbs. On former bikes I’ve owned; there were twin carbs on a Honda 305 motorcycle, three carbs on a 71 Kawasaki triple, and three deuces on a 65 Pontiac GTO with a 421. I certainly have no qualms in pulling my engine and doing what needs to be done. That’s how my 389 powered GTO became a 421 after I blew the 389.
Now with those that tried carbs with the HE engine, then switched to the fuel injection; was it because of drivability and performance issues with the carbs. A carbs fuel mixture and the engines ignition timing sometimes need to be adjusted to optimize the engines performance; as in dyno tuning. Before turbo chargers and blowers came along; higher compression ratios, along with longer duration, high lift cam shafts where used to increase power. I out grew my past, and am happy when all is as it was meant to be.

 

That PreHE engine is waaaaay more forgiving than any HE engine in any market.

The camshafts are unique to the carby set up.

The early PreHE Injected was still 9:1, and used a Bosch Analoge system. Slightly better than the carby version for emission restriction demanded by the USA.

I was involved with a 12.5:1 carby. It could be set up beautifully for power, but lost it for everyday driving. Then set up for everyday, lost it big time at the top end. Never achieved a satisfactory compromise.

Swapped the carby cams into it, much better, but still not as driveable as it should be, and certainly not as flexible as the V12 should be.

Let those cams in it (too hard to swap again), and fitted EFI. He used the Wolf 3D way back then, and that sorted it perfectly.

Another one here has a 1988 HE, and fitted PreHE pistons and heads, from his rusted out S1 V12, with 4 SU carbies. A few hundred hours of "sorting" and he is happy.

The HE you have is as fussy at hell with timing, and not much room to move sadly. Retard it a tad, slug, runs hot, drinks fuel. Advance it a tad, detonation at the top end, and piston damage. they really were on the edge. Your saviour, MAYBE, is the 11.5 compared to our 12.5.

The HE set up was designed for Fuel Infection, nothing else really.

 

Read you loud and clear; except for the Wolt 3D you mentioned ( wild guess would be electronic ignition timing control). I get your point; those high compression ratios are reminiscent of full race engines of the past, that were only suited for one thing. Nah; I've been there, done that; having no intention of going that route. Sounds like it would be a nightmare to dial in to be street able. I’ll be quite happy with my original engine once I sort out the issues I have mentioned. I’ll have a clicking tappet to shim, gas tanks to drain and clean out, and the same with the carbs. From experience with my fishing boats outboard motor not being used for a lengthy period, I know ethanol turns into a solid that’ll clog it’s 4 carbs, main jets; a PETA. All the XJ12’s carbs are much more accessible. So; I’m quite motivated to get my propane heater going, and get to work. Any tips on pulling the eng and trans will be appreciated. That’s probably already on this terrific forum. TY

 

Wolf 3D, is an aftermarket engine management system. NOT a fan, but it worked on that one car.

V12 out of the chassis, SIMPLE, but since we have 46C here today, I will call Beer O'Clock, and do a PDF during the day from memory and post it later tonight my time.

Have a look at the XJS Section, and a sticky I wrote at the top "V12 Oil Leaks".
I have used my HE as the model, so have not mentioned that gallery plug leak, as it was only the early engines that I remember. Also, yours may have a cartridge oil filter, versus the more common Spin On, and they can leak, run around the sandwich plate, into the tin flywheel cover, and out to the dirt.

Lots of suspects to eliminate BEFORE diving in the deep end.

 

OK, 10PM here and still 39C, Bugga.

The PDF is attached.

Any question, ask please.

 

I’ve lost track, is the carbed engine British or American? If American it will have 7.8-1 compression and not the 9.0-1 the British enjoy.

The problem is The distributor not the carbs. If you examine the timing curve on the HE and the timing curve on the Flathead or Pre HE you will instantly see the issue. The pre HE distributor is more in line with your needs then the HE distributor. More in line but not perfect. I wish I kept track of the changes I made. But I’m afraid I used a lot of left over springs in my attempt to recurve the distributor A fair bit of grinding & welding on the weights was required. To be completely honest between the Needles and the distributor work I’m afraid I at best got it close. I’m sure there may be more power, better fuel mileage and cleaner exhaust possible than I attained. The factory tuned and adjusted for 10’s of thousands of man hours meeting smog regulations and optimizing the engines potential.
Following my efforts It ran smoothly and seemed powerful but more than that I’m not willing to claim.
The only way a car can get better fuel mileage is if it uses less fuel. Therefore the HE is leaner then the carbs. The solution there lies in the modern fuels with 10% ethanol. Ethanol has a higher octane than gasoline which will help for the higher compression of the HE. But it has less BTU’s then gasoline. ( don’t worry Gasoline has less BTU’s than diesel, so if maximum fuel mileage was the priority use a diesel )

We have E15 available here and that proved the best solution. Most of the work with the distributor and carbs went back to close to original. Playing with the fuel should have been my first move.