Forgive me;


I’m doing an Engine swap. I’m taking a perfectly good, low mileage 4.2 and replacing it with a 5.3 HE, yep V12
I will retrofit carbs on it. Do I get credit for that?

 

Doug did something similar a couple years ago but I think he did FI.
As for credit, you'll have to talk to the V-12 guys about that, but I would give you 5 stars if successful.

 

Don't forget that although the V12 is all aluminium, it is still heavier than the six, so will need new front springs. Tyres on the V12s were also slightly wider, 215 instead of 205. They may have had an LSD too. Gearbox is different as well.
Say hello to 9-12 mpg too !

 

Not according to my scales. The 4.2 is 30 pounds heavier the the 5.3. Plus the 6 has the cast iron automatic and 3/4 of 1977 the GM turbo 400 was used and that’s all aluminum.
I’m further going to lighten it by getting rid of that bus sized alternator & go to a tiny GM 1/3 the size. Same amperage. Also that massive York A/C compressor? Trash. A little Sanyo A/C and since it’s a 1972 I don’t need the air pump.
All that extra space means air can flow through the engine compartment which will help cool it down.
Two things I’m going to do to improve gas mileage. I’ll put those carbs on an HE 11.5-1 compression . Might need to fiddle a bit to get the right needles. And instead of the 3:31-1 final drive I’ll swap in the 2:88-1 ratio of the HE. Combined with the tighter ratio of the TH400 to the Borg Warner I might get as high as 6 maybe even 7. ( if I’m lucky ) mpg.
Oh I forgot to mention my sedan will be pulling a very light weight XKE on an extremely light trailer.
I just think a Jaguar pulling a Jaguar race car has to be cool don’t you agree?

 

I think this project is very courageous! I have a 1972 V12 chassis - the engine has gone to be a work of art, and my original intention was to put a 4.2 engine in it. The body turned out to have more problems than i was willing to fix so the car will be scrapped eventually. I think you need to re-examine the weight figures, A V12 engine is heavier than an XK once you add the cast iron exhausts etc. The block is not light, and the crank is a monster!
The 3.31 LSD rear is bound for my running 1973 XJ6 once it gets its 4 speed o/d box. Will give me around 29mph/1000rpm in top o/d which the six should pull.
If you are really serious about this project then I may offer you the tacho and speedo from the V12. I have had lots of interest in these - they are rare.

 

Sorry, I got it wrong, but with the lighter weight you'll still be looking at replacing the front springs. The HE engines have a different cylinder head to the previous engines. The combustion chamber shape allows the very high compression ratio to work.
Have a read: -
The Jaguar V12 Engine / AJ6 Engineering
The chap who wrote this was a Jaguar development engineer when the V12 was in production.
All the best with your engine install, by the way ! Have you got a budget for a re-spray ?

 

Given the effort required in the project, I'd keep the injection and consider either a manual shift or a more modern automatic transmission with 4 speeds and lock up.

 

The Crank on a V12 weighs 78.8 pounds!!!! Yes it is heavy. plus those rods have almost a full pound each of excess weight. So then add the weight of those sleeves. Phewww! Yet I’ve had both on scales. And the 30 pounds lighter is real.

Those V12 cast Iron manifolds are the subject of a great amount of research by me. First each one is only a little over 4 pounds. I suppose with nuts and everything the whole set is about 18 pounds.
When I built a set of headers for my V12 XKE race car the tubing was way heavier than that. But I thought more power right? Well I never did a before and after so? However Robert Knodt did and it’s on His U tube channel. ( Camp Chaos) with Webers, cams, pistons etc it was 4%.
Now the EType is a lot more open than His XJS so my bends weren’t as tight and maybe I was a hair breadth more equal length but I’ll bet that’s really close to the most you can pull from a properly designed and carefully built set of headers.
If you wonder why a V8 gains so much power over a V12. Do a careful study of the firing order of a V8 and a V12.
I already have a set of the tachometer & Speedometer. From a 1973 I parted out back in the 1990’s total rust free car with a low mileage engine. Like dozens and dozens of others I scrapped. I used to be given rusty cars and save the V12’s Then checked them out and made sure they were in great shape. And tried to sell them on places like Hemmings. Barely broke even after paying for the ads.

 

Doing EFI is very straight forward except parts are getting harder and harder to find. Plus they are set up for straight gasoline. Most fuel now is at least 10% ethanol. ( which has real benefits). But effectively that thins the fuel mixture out. You can get by but you’re pushing it. The system has no way of richening the mixture to compensate. Well, the first series using the 3 Bosch units can be adjusted. But they are 45+ years old and a lot of the solder joints are corroded in nearly. Everyone I’ve looked at.
While a mega squirt or other aftermarket units can be used, the plug and play units are insanely expensive. And the rest while self learning take a lot of wiring professionalism to get working properly. Plus you’re still working with very old units.
Carbs on the other hand are lawn mower simple.
Potentially have more power available than EFI
I know the original V12 with carbs made 13 less horsepower than the later EFI and a couple mpg less fuel mileage
But if you put carbs on the HE with 11.5-1 compression instead of the 7.8-1 compression and use the later GM TH 400 instead of the Borg Warner transmission then swapped the 3:31-1 rear end for the newer 2:88-1 ratio The power will at least meet the EFI and probably better fuel mileage as well. And! you can adjust to whatever fuel is available. Even E85!!!!! That’s about 300 horsepower or maybe a bit more!!!!

 

Some people just luv carbs no matter what. You dont have to be one of those people. The early V12 fuel injection system can have it's mixture adjusted and fine tuned using fuel pressure. There are 2 adjustable fuel pressure regulators on the early EFI system. You could also buy a donor HE XJS and then you would have every thing else you needed, fuel injection radiator, transmission drive shaft, updated front and rear suspension. Series 1 suspension had many shortcomings, including cotton seals, less castor, sold front rotors and on and on.

Last year I bought a motor home with a rebuilt Qjet. It was rebuilt by a reputable and well know expert. It drove fine and I used it for awhile. Then I converted to TBI fuel injection, nothing else changed. Night and day difference. I got better fuel mileage and the RV did fine on short hills but on long up-hills it would start to fade after a while. With the fuel injection I could just turn the key and drive off. No stalling, bucking etc and it now could accelerate up the same longs hill with authority. I live at the top of a long hill that is one of the highest places on the Altlantic Coast so this was a phenomenon I observed many times. Yes, I know I could have rejetted the carb, adjusted the float and tinkered for days but life is short and that's not on my things I want to do list. Even a simple 80's self adjusting FI system that accounts for barometric pressure changes is a wonderful thing

 

Much of what you say is absolutely correct . The whole front crossmember from a series 3 will go in. Luckily it’s a straight bolt in.
EFI does offer some trivial fuel mileage and power increase but not as much as as apparent. For example the carbs are 237 horsepower DIN net. And EFI is 260 horsepower DIN net.
Those 13 horsepower are not just due to the switch from Carbs to EFI. The carbed engines only had a 7.8-1 compression ratio while the EFI was 11.5-1 that also accounts for some of the improved fuel mileage. On the other hand the timing is altered. With the later HE engine I get the 11.5-1 compression. So perhaps the best option is the early distributor in the later engine.
I doubt the stock Stromberg Carb needles will exactly be right. But altering carb needles is a breeze compared to trying to alter EFI. In addition if the whole needle needs to be richened up it is simple to ream the jets rather than try to duplicate the whole stepped needle on 4 needles.
I’m addition the various gasoline types also help. For example E10 needs about a 2% richer jet than non oxygenated fuel. E15 needs about a 5% richer jet. And E85 requires a 20% richer Jet.
The 20% more power ( from E85) gets you 312 horsepower DIN net from the stock 260


Plus the superior TH 400 transmission.
In addition the 1972 final drive ratio is 3.31 while the later drive ratio is 2.88

But E85 uses more fuel. About 10% more. Assume EFI gets 15 mpg. E85 will get 13.5. Mpg.
If we buy non oxygenated premium recent price was $4.39/9 while E85 was $1.99/9
A 500 mile trip on Premium would cost $146.xx
while E85 would cost $74.xx
In addition the E85 runs seriously cooler. Important since Zi will be towing the Jaguar XKE race car with this.

And the normal carbon deposit on the back of the intake valve would not be there EFI is batch fired on the V12 so gas is squirted in and the camshaft decides when to open the valve to let the fuel/air in.

 

The weight I save will help with the added weight of the race car and trailer. I’m shooting for a trailer weight of 500 pounds. Maybe a little less. Have you ever lifted the frame of an XKE ? That is only 22 pounds. Yet that holds up a 730 pound engine capable of 183 mph on the Mulsaine straight. It’s really thin wall square tubing that is brazed, not welded. Plus it has passed the US crash tests That’s engineering!!! That has inspired the design. ps I’ve built and sold a lot of trailers so I actually know what I’m talking about.

Basically the combustion chamber is a version of the Buick Fireball of the late 1920’s used by GM in Chevy’s through the early 1960’s.
Chrysler tried to achieve the same thing but that was unsuccessful. The so Called HE engine was achieved by retarding the timing instead of advancing it. In a light load ( cruising instead of accelerating ). The timing can come up to reasonable. Under acceleration the timing is held back that’s why the HE feels doggy from a stop
In reality it’s far worse a design than the 1971-1980 so called Flathead, heron, or Pre HE just to improve fuel mileage by a mile per gallon or so. If you notice the compression ratio is low, as low as 7.8-1 on the early 1971-1980 engine. yet it made the same horsepower as the higher compression ratio.
Racers get some real power out of the earlier Flathead/preHE compared to the HE. The reason is every time you change directions on the intake power is lost. There are 4 direction changes on an HE compared to 2 on the Flathead.

The other improvements came from other changes such as the GM turbo 400 transmission replacing its the Borg Warner transmission 2% slippage compared to 4% on the Borg Warner. , an updated fuel injection system, a 2:88 final drive over the 3.07 or 3.31 final drive

Regarding the respray1 gallon of lacquer and 2 gallons of lacquer thinner isn’t that expensive
nor will it take that long to do. I’ve painted plenty of cars and working with lacquer is a real treat compared to modern paints. At 51 years old the paint job has held up remarkably well, no rust. Very straight body. A light scuff with the 320. Tape off any thing not removed. Maybe a day or less. Cut and buff the next day.

 

The E-type front engine and suspension cradle is not brazed, but "bronze-welded". This is a much higher temperature process with a different, (although similar) filler metal. One would think that the tubes would be better welded using the traditional welding process for steel, but the tubes used by Jaguar were made of Renolds 531 alloy that is not suitable for welding but gives the strength required. Renolds 531 was very commonly also used for bicycle frames. The bike my father bought for me when I became 11 years old was of this alloy, but brazed because bike frames commonly used lugs into which the tubes fitted and were then brazed in place. The Jaguar frames don't use lugs, the bronze welding "glues" them together.

Nowadays one can only buy 531 on special order, as the alloy has been superceded by more modern and, (maybe), better alloys.
https://en.wikipedia.org/wiki/Reynolds_531

 

The E-type frame and Formula 1 space frames followed a practice that had been established with motorcycles most significantly Norton's Manx Featherbed.

 

The E type frame is directly evolved from the D type frame which was first produced in 1954. Since it’s 1” square tube.
I’ve never seen a square tube motorcycle frame, and the loads on a motorcycle are significantly different than those of a D type I’m forced to question the validity of that statement. I suppose it could be possible? I’m not familiar with that motorcycle. Exit. I looked up the Norton featherbed on Wiki, and as I suspected it is round tube. I’m sorry but I fail to see the connection.
I know following WW2 the formula 500 machines used single cylinder 500cc motor cycle engines and they too used round tube frames? Unless you consider that the connection?
Many of the Jaguar engineers of that era came from the WW 2 aircraft industry.

 

Thank you. The exact alloy escapes me. Same with the “welding process”. I did try to repair a crack in one frame using a traditional TIG welding process and found the cracks forming upon cooling. Since the frame was ruined anyway. I tried a lot of variations such as pre heating various gases. Different welding Rods etc. All without success.
At that point I simply grabbed another ( used ) frame and went on. A few years ago I replicated the frame in Chrome moly which does take well to TIG welding but I notice it’s not as Rust resistant as the Renolds alloy. So very well selected Jaguar.

 

My comment related to how the tubes were joined together, which is what we were discussing, not their cross-section. Brazing and bronze welding were well established in the motorcycle world especially for thin wall tube. Though round rather than square, you will have seen that the Manx Featherbed was also Reynolds 531 tube.

 

Fair enough. I understand the connection now. Thank you

 

I’m building a XJS group 44 tribute car at the same time. I have a set of Webers, a set of SU’s and a set of Strombergs. In Addition to several sets of EFI. That will be EFI. ( reasons later)
Making the 1972 into a V12 I’m jumping the factory by a year so originality isn’t a big deal.
I’m kinda toying with the idea of using SU’s instead of the Strombergs.
The reason is E85. Yep 85% ethanol 15 % gasoline. Here’s the reason. Premium sells locally for $4.59/9 a gallon. It is 91 octane!
E85 sells at the same pump for $2.19/9 a gallon. That’s 1/2 price. Its octane will be between 104 & 108 octane. So I can advance the timing.
Normally with E85 you get 20% worse fuel mileage. But with timing advanced you pick back up some of that.
Have I mentioned I intend to tow my Jaguar XKE race car with this Sedan? Yes Jaguar Race car pulled by Jaguar sedan!!
One other big advantage of using E85 is how cool the engine runs. Lugging 2500 pounds up steep hills or even mountains. It’s nice to have things cool.
So in addition to saving almost 50% of the cost and running cooler than stock by a lot. It also makes about 20% more power. That’s over 300 horsepower. !
Yes I can modify a EFI system and do the same but somehow it’s not going to be as much fun.

 

.


I’m tempted to try to re- buff the paint just to see how good it can be. ( I love the Lacquer used in these).
But probably will do a complete respray.
I’m Hoping to do it with 1 gallon of paint. Since all the door jams and engine compartment still look good. Besides I use a lot of lacquer thinner which evaporates and leaves thinner coats. ( my secret to spray Lacquer without cracking after 50 years).

The windshield and rear glass is coming out anyway to replace the rubber. So I’ll just mask off the opening. I’ll Remove all the chrome, ( it’s easier than doing a proper job of taping everything).
I‘ve got a big compressor and several spray guns. But this will be my last paint job. At 75, it’s getting hard to do a full body spray without having to sit and rest. I’ll rest between coats.
I know a full paint job needs 2 gallons. But am hoping just an overspray won’t need as much paint.
Getting Lacquer is going to be ordered on line. Nobody stocks it anymore. It’s all 2 part, base coat clear coat.
That’s too bad. Every single paint job I’ve done ( except 1 ) is Lacquer and while I’ve won awards and my first paint job is still brilliant and decent looking. I’m really a lousy painter. Just good at sanding off my mistakes.


Oh, regarding the HE engine, don’t let anybody tell you it’s better. Pure and simple it was designed to meet California’s coming smog rules.
Both the preHE and the HE have the same power rating by the factory. A general rule of thumb is for each point of compression you gain 10 horsepower. For America going from 7.8 to 11.5 should get us near 40 additional horsepower. We got nothing!
The original Buick fireball head it was patterned after. Used until 1953 ( and Later used in the Chevy 6 cylinder engine until 1961) was a way of burning lean fuel mixtures (by forcing the intake charge over the hot exhaust valve). At least May gave proper credit by calling it the fireball head.

We racers always want to work with the early head. Without the combustion chamber in the way. When the intake valve opens the full charge can go all the way to the cylinder wall which because of the angle it enters, imparts the required swirl. The squish is given by the top band of the piston but with the piston on the way up. Thus no restriction by forming things in the combustion chamber. Short of a 4 valve head, it’s the best flowing design.

Finally re lighter weight? You do realize how little 30 pounds spread over the length of the engine is going to be? That’s like having a 6 year old kid instead of your wife in the front seat. Well maybe even less than that!