I want to explore options to increase power at a modest cost.
I’d like to explore Putting a pair of 5.3 heads on a 6.0 engine in hopes to get the compression higher.

E85 allows effective octane in excess of 100 compared to the 91 or at best 93 octane gasoline available at the pump. That plus the benefit of extra oxygen allows more fuel to burn giving at least 10% more power. More so if the compression is higher.
plus the slower flame front of an alcohol flame burns further down into the cylinder.

 

I assume you're taking about the benefit of spark advance on E85, which is huge for low end torque. I think the volume of fuel you'd flow is quite a bit higher. Which would displace some oxygen but I think the spark advance would more than make up for it. How would you control spark? It would also cool your exhaust temps.

 

With a distributor it’s very simple to advance the timing and since the machine work is already done it’s simply a matter of grabbing pieces off a parts car.
The very last V12’s are reported to have OBD2 which might allow some reprogramming.
If you can get a Megasquirt to work the reprogramming is straight forward. The problem is getting the Megasquirt to work with the British sensors seems to be the stumbling block.

Alcohol carries free oxygen which is why it makes extra power. The free oxygen will burn more fuel and that’s how you make more power. But the 6.0 is down a point of compression. From 11.5 down to 10.5. Now if they did it by shortening the piston deck height, swapping heads won’t achieve anything. But if they did it by opening up the combustion chamber, going back to the 5.3 heads will raise compression. I know the valve sizes are the same but with a little work you can use the 4.2 valves and gain valve size. Combine E85 with a camshaft more suitable for racing than hauling fat guys and their golf clubs around and the potential for serious power gain is there.
Don’t forget Group 44 made 450 Horsepower on 4 Stromberg carbs. With about that compression and Crower reground camshafts.

 

Might be irrelevant but you can make your own race gas with Xylene from the local paint store. It sure made my car whistle like a turbo diesel.

as for race spec upgrades one other item is to insulate and isolate the intake, filter box, and air flow. I believe TWR found 20+hp just from heat shields under the manifolds.

you can easily buy a roll of duct wrap (reflective commercial grade hvac insulation) or go the extra mile and ceramic coat your parts which is my intention.

The wrap is like any Turbo Blanket you'd wrap and tape as if it were a ventilation duct. Cheap and easy. Need to 'pipe' in cold fresh air there are mods to cut through the light housing or follow the 6.0L design which sucks in from the top of radiator.

Then there is exhaust which must be gutted but thats another story.


Edit:

Cant remember the exact combo but I read here some one mentioned putting HE heads on pre HE engine would net 23:1 compression (roughly) or vice versa...something to think about. 23:1 is diesel territory

 

All of those are well known. Simply by cutting off the air horn on the air filter there is an extra 10 horsepower plus cold air adds the other 10 For the 20 you mentioned. Removing the mufflers and resonators adds in a full 20hp but if the e haunt pipes are increased from 2” to 2&1/2” there is another 20 horsepower there.
E 85 ( which is 85% alcohol but still qualifies as a gasoline ) will add 10% + to the engine. More since that % is based on 9.0-1 compression and Jaguar has either 10.5- or 11.5-1 compression ratio. But you must advance the timing to take full advantage.
If you’re using the 5.3 timing is something like 17% BTDC while using E85 will allow 36 BTDC.

The stock camshafts fall off at about 5500 rpm while the engine has been tested at the factory safe up to 8300 rpm If you have your camshafts reground to a fairly common profile that most cam grinders have masters of you can easily add another 80 horsepower. I use Berry cams they are close by and I can drop them off and pick them up. Isky and Crower both have experience. Crower did all the cam work for Group 44. Both Kent cams and Piper cams in England have a better profile that’s good for more than 100 horsepower. But That requires shipping back and forth from England Plus they get a real premium

 

how fast do you wanna go,, how much money do you want to spend, its that simple!
ron

 

Sorry Ron but it isn’t. This summer I’ve seen an average of 3 XJS’s a month sell for less than $500 at the various Auction sites. Granted some may not run and a few had superficial body damage.
In addition if you check out Facebook and Craigslist you see even more.
Between early sedans and later parts cars damaged in the front it wouldn’t be too hard to get a reasonably quick car for less than $2000 and your labor. Finding a good Used Chevy manual transmission for a modest price Shouldn’t be that hard since they just came out with a New 5 speed Capable of dealing with 500 horsepower That sells for $3000.
That should get you around as fast as Group 44 did when it won the championship.
Yes you can spend massively more money and go a little faster. But maybe not enough to overcome a skilled driver.

My first year of driving vintage wheel to wheel I thought I was fast. The next year with several races under my belt I was 10 seconds a lap faster in the exact same car. The following year I again picked up a few seconds.
This was after all the races I’d entered since I was 14. Dirt track circle track, sprint car racing, drag racing etc. even sports car racing. Where I got my SCCA national license driving an XK150 in DProduction.

My point is you can have a lot of fun for not much money and spending isn’t always part of the equation.

 

its putting the early heads on an HE gets you into diesel territory. But you actually can’t do it because the valves stick down and the piston is flush with the deck. Clang!

 

MG you finally said something logical , thanks!
anyone who has taken apart both an Pre HE V12, and a later V12 ! HEcould see that piston problem!
OK the PRE has the combustion chamber in the piston crown/top@
the HE has the chamber in the head, lot of surface volume , not good for extreme compression/heat!
two completely different engineering designs!
ron

 

What, out of curiousity, is the path forward if come hell or high water your determined to convert a V12 to run diesel at a more traditional compression ratio? Keep in mind modern diesels can pull it off at 16:1 with better turbos etc.

 

I don't think it would be easy. You'd need to have injectors to put the fuel directly into the combustion chamber, and diesel's usually have a bowled piston to form the combustion chamber. You'd need a control system too, a gasoline ECU won't work. If it isn't turbo I doubt it would put out that much power, in comparison the GM 6.2 was 130 hp

 

Considering diesels are designed to run much slower than gasoline. You’d need some way to plug the spark plug hole, totally different camshafts. Pistons that will work. Mind you the combustion chamber would be in the piston ( heron head ) but to keep compression up it will be hard to provide valve relief pockets and some sort of combustion chamber without dropping the compression too much.
That doesn’t cover any of the unknowns such as oil timing requirements ( do diesels need oil earlier in their rotation than gasoline engines?) Ability to provide direct injection Etc. I’ve never messed with diesels So I’m not really the person to ask.

 

Going off the top of my head old Ford engines were not direct injection so a poorer platform to crank out power. My 6.0L diesel has high pressure oil operated injectors to overcome compression and slam fuel in at something like 1200psi. It would have to be based on earlier diesel designs I dont see high pressure common rail direct injection in a V12 without a years' salary in engineering.

And at that point you might aswell take Ron's suggestion and buy a god damn audi twin turbo V12 and just do the swap.

Edit:

this is what i was thinking of basing it on https://en.m.wikipedia.org/wiki/Inte..._Harvester_IDI mechanical system (later had turbos which is necessary) now keep in mind diesel might seem slow but its a platform that scales up very easily. My truck gains 250hp and god knows how much torque just by tweaking the computer.

 

The current Jaguar diesels fuel pressure is 29,000 psi. Make a mistake with that and the pressure will slice through steel.

 

Well. 20 years of engineering can do alot.

I prefer older tech it doesnt blow apart killing families in a walmart parking lot with supersonic projectiles! Haha! Even my 2003 diesel is annoying in its over-computerization.

 

to take a V12 jag and convert to diesel fuel is just not logical , mainly because of the over square bore/ stroke combination!
1st a good deisel engine should have a long stroke and a bore smaller than the stroke , Big bucks to do properly!
2nd Jag would need a completely different cylinder head casting ,hell it dont have anywhere near enough hold down studs, diesels do NOT lend themseslves well to OPEN deck blocks.
it would be best with a flat surface , but many changes like said direct chamber fuel injection, and associated pumps and pieces,ETC.
SO my old dream would go back to that DAMN GOOD Audi V12 Diesel twin turbo!
in the end it would be cheaper, and the research /engineering would be all done , that Audi is top of the line in Diesel engieering!
and you would not have to take the Audi engine apart, just outside ancillaries, oil coolers, coolant coolers,air charge coolers,etc.
plus other things i know i have forgotten! most important would be the Engine control unit computor, and modifiying it , fuel and timing adjustments!
damn would i have fun those toys!!!
ron
i;m sure a V12 audi diesel is available in Europe/ Germany!

 

Diesel's have made huge strides in the last 30 years, primarily due to better engine management. Gasoline as well, who would have thought 30 years ago that a 2.0 4 cylinder would make 300 hp ( like in the F Type) and be perfectly drivable on the street and have a good idle?

The indirect injection diesels have lower thermal efficiency than direct, and they don't respond very well to turbocharging. Revs are usually limited too, the common rail diesels now rev about the same as 70's vintage domestic gas V8's did. Maybe better, as a Jaguar V6 diesel can rev to 4500, and in the 302 in an 80's Town Car it was all over by 3500 rpm.

 

If you really want a V12 diesel why not just buy the Audi? Likely it would be tens of thousands cheaper than trying to getting the Jaguar working?

 

Ron, have you checked out the 6.0 cylinder head? Did they increase the size of the chamber or simply drop the piston’s height? Somehow they are a full point lower than the 5.3 from 11.5-1 down to 10.5-1 in the 6.0 liter. Normally if the engine gets bigger compression would go up if no changes are made.

 

they increased the in HE head chamber volume, and changed the exhaust port shape to a tighter turn, not good for flow!
the piston is flat top and comes only close to(a guess about .100 thou down from top!).

someplace on this site a pic of 6L piston?
an old pic of the GM chamber of recessed exhaust valve(kinda like the basic FIREBALL Buick chamber(altho not the same exact).
ron

TWR race piston forged Cosworth, 12.5 ratio chamber centered in middle! for Flat chamber Heron type. they also milled heads flat by 050. thou. and the valves protruded from the surface reduce shrouding ,more flow, and custom valves, but factory sizes( MAYBE ?).

very old GM chamber, shows small hi swirl that burned up many ex. valves just like HE engines did.