The BW to TH400 change was late 1976, so there are plenty of pre HE engines with the TH400. 3.07 to 2.88 isn't a huge jump, and in non highway cruise driving doesn't make much ( if any difference).

My experience is with the V12 sedans, so there were no changes in the body between pre HE and HE Series III cars. I know that I can get 22-23 mpg on the highway with an HE while the pre HE struggled to make 14 mpg. One of the UK magazines tested a pre HE V12 and got 11.4 mpg - imperial gallons too, with are 20% bigger than US gallons.

At part throttle there is charge stagnation in the pre HE combustion chamber that requires overfueling through much of the operating range, while the HE does not. That in itself improves both fuel economy and emissions. The Pre HE had the dubious distinction of being the first car in the UK to require emission controls to meet the lax (at the time) UK emission standards, when other cars on carbs and no emission controls could meet the standard. It's much easier to meet California emissions if you don't have to overfuel.

The HE has the high compression, but it also used a semi-stratified lean charge of air and fuel, so you won't see as much power increase as with a stoichiometric mixture. Compression is only part of the story there and can't be compared directly because of the mixture difference. The HE produces almost 30 ft-lbs more torque than the pre HE, and that will increase fuel economy by allowing smaller throttle openings to accelerate

The biggest reason for the HE to exist is at the time it was becoming very difficult to sell large, fuel thirsty cars. The world had just had the second oil crisis in 1979 and a cars that could barely get double digit fuel economy numbers was quickly becoming unsellable. Jaguar had come to the conclusion that the V12 would cease production unless the fuel economy could be dramatically improved as it would be simply uneconomic to make. California emissions were not a deciding factor, economic viability was. In 1980 Jaguar only made a couple hundred V12 cars , both XJS and Sedans and was haemorrhaging cash. They needed something to make the V12 sellable, and to be sellable it needed to be more "socially aceptable" - and driving a gas guzzler at the time was not acceptable in times of shortages and in the UK there was plans to reintroduce fuel rationing. The Pre HE had outlived its usefulness.

 

The 1967-75 Suez Canal blockage caused a steep rise in price of gasoline in Britain right as the V12 was introduced in 1971 Actually it had been intended to be introduced earlier but delayed because of development problems with the originally intended Fuel injection.
As a last minute lash up carburators were Hurriedly substituted but because of hood clearance problems and the resulting winding inlet path 20 horsepower was lost.
When finally fuel injection was used in 1975 by sourcing 3 Volkswagen ECM’s it too was a real kludge job. The injectors were oversized in order to deal with cold start Issues in North America.
Eventual switch to the Lucas ECM improved fuel mileage and further improvements were made as attention to fuel shortage in America drove up fuel prices.
Realize that California represents more than 50% of Jaguar’s sales and California had a serious issue with smog. The notified manufacturers of their intention to implement the new smog laws by 1977 giving them time to meet The new requirements of 1981.
Sir Lyons had invested heavily in the V12 going deeper in debt than at any time in his career. The Blockade, the American fuel shortage, and California smog laws caused a perfect storm with sales of the V12 taking a severe hit. Some years only Around 1000 V12’s were sold. While sales of the old cast Iron 6 in the sedans also took a hit.

Micheal May’s revised head was not a new design. Buick had introduced that in the 1930’s and by the 1940’s it had moved over to Chevrolet. they both called the design the Fireball which Michael May have a nod to in naming it.

The design is flawed in two ways. First the recessed valve needed to concentrate a lean mixture around the spark plug decreases flow. ( every change of direction of a mass like air and fuel ) slows and reduces volume.

Second to concentrate the fuel enough in light cruising where fuel is lean without misfiring requires higher than normal compression. That high compression causes preignition or pinging something owners of luxury cars won’t tolerate even if the parts could withstand it. To deal with that the timing is pulled back by nearly 20 degrees. Retarded timing hurts fuel mileage but is required to keep from making the pinging noise, and keep from burning valves and pistons.

So if you were to say Better fuel mileage under light cruising I would agree with you. And if you were to say Reduced emissions I would again agree with you.

However better efficency when much of the improvement can be attributed to other factors I’m afraid we will have to disagree.
To be fair Jaguar was in trouble and marketing slogans work. It markets better if there is something new than if they were honest and said we copied an old idea as a crutch to get around the problem.

My final authority is AJ6 Who limits power output of the HE engine in spite of modifications to 450 horsepower

 

So what? You said you basically had no budget and were using stock engines. A stock HE produces more torque across a broader rev band than any stock pre HE, Jaguar's own test's show that. Since they weigh the same I'd pick the engine with more power/torque and that's an HE, assuming all your potential engines are in similar mechanical condition.

And by the way, all of the Jaguar USA sales in 1980 represented 16% of Jaguar's global sales, so California sales were a small percentage of Jaguar's total sales. At the time, the bulk of Jaguar USA sales were New York and Florida. California laws certainly didn't make or break the viability of the V12.

 

There is power available in V12’s that cost little or nothing As I explained but apparently you failed to read; the little air horns on the stock air filters were designed to muffle intake sounds. They choke intake air and what air they Do get is hot off the radiator.
If you remove those and fabricate a 4 in opening In the filter housing drawing cold air from in front of the radiator there is horsepower there. In addition the stock timing can be advanced several degrees depending on fuel available. There is a few horsepower saved by the deletion of the cooling fans. Deleting mufflers cat converters is another source of power gain

We here in the Midwest enjoy cheap E85 ( up to 70 cents a gallon less than premium ) which is up to 85% alcohol .ethanol Alcohol Has 114 octane Plus extra Oxygen which allows more fuel Too burn to make more power.

E85 will add at least a 10% improvement of power over premium. Plus with its higher octane timing can be advanced. More than you can with premium.

The final gain is the modest cost of regrinding the camshafts. Regrinding a 6 cylinder camshaft costs $112 do a pair is going to cost me with taxes less than $250. It’s been a while since I’ve reground Jaguar camshafts. But I believe you can grind nearly .125 from the base circle. I should go downstairs and measure a few cams to be sure. The additional lift and duration will help on the race track where you’re rarely below 4000 rpm.

Yes I know Kent and Piper both have great camshafts available ( Better than I can get locally ) but they cost a great deal more than my local regrinder and there would be shipping back and forth plus likely import duty.

I still have my ball mill so I can clean up the intake port. Plus I have the set of stones to do a 3 angle valve seat. Those two will hurt low RPM power but gain at the top end.
You mentioned torque? Look at where the torque advantage is and then remember in racing we normally race in 5500-7000rpm range . With reground cams instead of running out of breath around 5500 we will go to 6600-7000 rpm and if the cams let us make power up there we try to stay as near to that as possible.
Each of those free or modest changes only ad 10-25 horsepower but remember those are cumulative but together on the race track make a significant improvement to the point where the flow restrictions of the HE heads start to limit power.

While there is things that can be done to improve flow in the HE heads each significant improvement in increasing flow reduces compression negating the one advantage The newer HE has. However with that lower compression timing can once again be advanced. I know there are a few people working or have worked on trying to improve performance of the HE head. It sure would be worthwhile to find out if they have crossed the line. Where it can net more power at higher RPM than the early flatheads

I’m in # 5 on the pole David Love is next to me in the first Ferrari Testa Rossa The D type behind him is the 2965 LeMans winner And behind me is the one of Factory Corvette SS The field also had a Porsche RSK a type 61 Birdcage Maserati. Etc.

 

Sir Sterling Moss and Myself sharing the podium at the 1986 Vintage speed week In the Bahama’s.
Yes he won overall but I did manage to beat his Aston Martin DBR 2 in one event and come in second.

 

1984 Bahama speed week where we could street drive the Race car from our hotel on the Beach to breakfast and then to the race track. I’m sure I annoyed the hotel guests with that loud unmuffled race car with megaphones At 6:00am
U

 

Building my XKE V12 roadster in the early 2000’s The top picture is the whole rear axle assembly rigidly mounted to eliminate bump steer . Notice the trailing arm coming in at a 45 degree angle to pivot at the same pivot point of the inner lower suspension arm. the bottom picture is the cockpit with my custom dash ( still using smiths gauges) the round aluminum tank is the 5 gallon dry sump. the roll bar is patterned after Group 44’s famous XKE

 

This is one of the 3 engines built for the XKEV12 my first attempt at bore and stroking. I offset ground the crankshaft and used off the shelf connecting rods. Aries piston @ 13-1 94 mm and a Isky XM5 reground camshafts
it was pretty well the mutt of the three engines. Only making 510 horsepower.

The yellow one I used Piper billet cams and 1.900 intake valves with a little work on the exhaust ports that went up to 591 hp but it was so flat from 6500-7800 it was my favorite.
the Aluminum one with more port work broke 600 hp ( 603) but was just too pesky I suspect it was over cammed

 

Here’s me with a little shifter cart I built and ran around the pits at Elkart Lake.

 

My favorite race track , Elkart Lake Wisconsin. it’s 4 miles long with 3 brutal straights and 9 of the 14 really tough sharp corners that really cook your brakes as you haul down from high speed. You’ve got to have power, brakes, great handling ( the carousel is an off camber 260 degree corner that leads onto the back straight) plus aerodynamics To push all that air at 160 + mph on 3 spots on the track. Fantastic food in the concessions ( reasonable prices too since they are run by church groups etc) Hills and woodlands and a charming resort atmosphere. Antique shops. For the ladies And such a friendly atmosphere.

 

As a young Navy Flyer I built this in the San Diego Navy hobby shop back in 1968. Raced at Holtville, Riverside, And Laguna Seca I think I can admit now that we used 115/145 aviation gas because zi had 13-1 compression pistons.

 

You did read where this is for a race car? You are aware that race cars run around race tracks at very high revs aren’t you? The only time we are below 4500 rpm is leaving ( at the start of the race) or returning to the pits. ( at the end of the race ) And gas mileage really doesn’t matter. Most sports car races are sprints 15-20 laps.

 

so this means you are today a yesterdays race car driver/builder!
most here want a good fast road car, not a loud fussy thing!

 

I’ve never pretended to be anything but a racer. I’m proud of the modest budget I’ve done it with and believe that Jaguars make fantastic race cars for a modest budget.
I don’t think Jaguars performance potential ended with the V12 although That’s probably as far as I’ll take it.
The new V8’s. Or even the electric cars are certainly worthy.
Ron you see to be implying that Jaguar’s are for posers pretty with a reputation for performance.
I think people should actually use the cars full potential. Show up at a track day and go wheel to wheel.

It’s OK if someone wants a numbers matching polished pretty thing. But my thrill is braking on the absolute edge of control in to a sharp corner stealing the best line and diving ahead of him at the checkered flag.
I loved watching Sir Sterling Moss best a competitor into the corner by using the exact same bit of cheating that had used on him a race earlier.

As the car dances a whisker away from total loss of control on the high speed banking, I feel more alive more intense, more thrilled, than since the last time I flew into combat.

Yes it takes courage. And skill. Maybe a whisker of luck. But it’s real. And it makes life worthwhile.

 

Hello Ron.
I hope I’m correct in remembering you once took. your Jaguar to the Texas mile And ran it to its top speed? Isn’t that a thrilling experience?
That’s the part of Jaguars I want others to share.

Sure There are a lot of fun, nice things about Jaguars. Safe social gatherings. Car shows, rally’s, etc.

Nothing that can’t be done with almost any other club or group.

What makes Jaguar so special are those LeMans wins. The club racing wins, Group 44’s wins in IMSA Trans Am wins. Tom Walkinshaw’s group A wins XJS AT Bathurst

 

please post a picture of you today, time does change us ALL , me included!
ron

 

Ugh.! I’m old fat and never was handsome. But I will if you will
Not quite sure why though? Can I post some pictures of cars or engines instead?

 

Not that difficult to do with a soldering iron and a cheap EPROM burner, the main fuel table is very easy to find. i had a brief look at the code in my ECU but as I'm stock there is very little to be gained from fuelling changes.

 

While waiting for an opening in the Navy flight training program I took electronics courses. While I passed it’s something I really Learned to hate to do.
When I sit down With the schematics and try to follow what’s going on and why it’s like relearning French all over again.

Mechanical fuel injection is So simple in comparison that I enjoy it. Same with carburators be it a simple SU or a Weber IDF. Everything is logical. This lever moves that and squirts fuel based on the size of the jet or stroke of the pump.
Once OBD2 came out even EFI fell into place. But early electronic fuel injection? Especially analog systems like Jaguar’s?
Sure part of the trouble is developed resistance from soldering connections made 40-50 years ago Or loose ground wires from assembly line workers angry with management.

The very earliest systems had that dial you could change from rich to lean. Why can’t we still get that. New systems have an E-Prom That effectively allows those changes.

 

The 6CU is analogue, later ECUs are digital. Early EFI is a great deal simpler than later EFI which has all the emissions code and extra I/O to support all that. I have run an emulator on a 16CU with free software that allows real time fuelling changes but at $175 it would eat up most of your budget.