Where do you intend to run the pipes under the car?

You could run them down inside the chassis rail skirts but this would require cutting the sides of the car. There is very limited room under the XJS. I'll get under later and take some photos to give you an idea of how much room there is under there.

The pre 1980 had 9.0:1 or 7.8:1 depending on the market either would be ok for some boost. The older XJS also came with 3.31 rear end ratio in the USA

 

ive been thinking from the beginning that i would pull the mufflers out and put the turbos there, then run the pipes back the same way the exhaust is routed. like i said, ive had the idea for this project for a year or so now, and i just finally got a good job to support it, so i dont yet have an xjs to go out and look, measure, brainstorm, etc.
i appreciate the pictures. im interested to see what ive got to work with.
is there any way to tell in the vin code what the rear ratio is? i thought you could only get it in 2.88. its good to know that i might get lucky.

 

You do not have enough room where the rear mufflers go to mount turbos without cutting out the rear panels. You will need a MIG welder.

Also there is NOT enough room under the car to run exhaust and intake from front to rear. There is NO WAY IN THE WORLD you will run 2 sets of pipes back the same way. The largest pipes that will fit through the cage 2.25", 2.5" WILL NOT FIT these must be run under the diff.

The XJS came with 4 different diff ratios and 2 different Diffs some have a Dana 44 and some have the Sailsbury GKN. The rear discs are differnt between the diffs as well.
3.31 and 3.07 in the pre-HE models depending on the market. USA and Australia got 3.31 and Europe 3.07.

All HE's came with 2.88

6 cylinders came with 3.54 as did the 6.0L with GM 4L80e transmission

I am in the process of installing 4.09 from an XK150.

The first 2 pics show the rear muffler tunnel the second pic my first finger is on the chassis rail that runs inside the tunnel, how do you plan to run 3 pipes in there?

The 3rd pic is the room to run pipes in the tunnel. Don't even think about running pipes lower than this or you will not be able to get over even small speed humps.

The last 2 pics show how much room you have to run 2 pipes back into the engine bay, this is the LH side of car the drivers side has even less room due to the steering column. The last pic you can see the steering gaiter just in front of that and very low is the front subframe.

DO NOT buy a car based on being a specific model for the engine or you will end up spending a considerable amount of money fixing the body due to rust. Buy a car that has minimal rust. Mine was a NO rust car but it still had some rust.

You will also need to budget for fixing other mechanical issues such as rear brakes. These are very difficult do and more often are totally stuffed unless you buy a well maintained car and then that is $$$$.

 

boy there really isnt much room to work with.
im probably gonna put some 18"s on it. hopefully thatll raise it up enough to clear the pipes and the turbos.

also, do you guys run catalytic converters on your cars?

 

Now is converting an H.E. to a flathead a simple matter of switching the pistons and heads? are the two blocks the same? are the rods the same? cams? etc?

 

dont waste your time on a 5.3L V12,, just locate a factory 6.0L, 92-97 XJ, made by Ford, and be done with the basic engine. the 6L comes 1/2" stroked.
add your own ideas of outside ancillarys, ECU-EMS, turbo it ,remote types, control detonation.

its old fashioned to modify engine internals, when much better engines are available STOCK.

besides you will probably not make extreme power anyway!
ask yourself ,, how much power do you want, 400hp, 600hp,, 1000hp 1400hp, what would be adequate?

and again reading thru the OP posts, you seem to be on a novelty plan.

 

i want a pre-facelift car. the facelift jags just dont do it for me.
im looking for around 400 horses. nothing crazy. its not gonna be a drag car. i just want to build a fun DD with a 5 or 6 speed.

 

400hp hmmm why are you wasting your time with pre-HE vs HE with this power level the HE will make 400hp without FI. Lister made 550hp NA and 700hp with supercharger on a HE from 6.9L.

Stroking the V12 is reletively easy compared to Twin Turbo. Offset grind the crank to accept large journal 6.0" chev rods (gives 80mm stroke) and use Holden 202/186 pistons will give you 6.5L. Cheaper still bore it for the 202 pistons for close to 5.8L and an easy 400hp+ depending on other mods.

Or just leave it standard and convert to manual first with a few breathing mods for around 300-330hp. Then look into modifying an engine. My 2c

Which ever way you go with the V12 budget for at least $5K for the engine and another $2-3K for a manual conversion if you use the Dellow kit with Toyota 5spd, this is the cheapest option if it does not have ABS.

The ONLY benefit of the pre-HE head, is it will accept larger valves for better TOP end power at the expense of midrange throttle response and fuel consupmtion.

 

ok well since it shouldnt be too crazy to get good hp NA, know any good vendors that are cheap? headers, intakes and such?

what do the 6" chevy rods come out of? and what motor do those holden pistons come out of?

 

oh, and do you guys know of any vendors where you can get gaskets and bolts cheap?
head gaskets, oil pan gaskets, water pump gaskets. head bolts unless theyre not TTY.

i cant find anything for these motors.

oh, and whats the engine designation for the HE? like i said earlier, i was thinking it was AJ6

 

Heads use studs and can be difficult to separate from the block google Kirbys XJS book and download it he has a good cheap head puller among other things.

Gaskets can be obtained from a number of sources I know Cometic do head gaskets for the V12. Also available on eBay

V12 HE

6" Chev rods from a SBC
Holden pistons from a Holden 202 inline 6cyl look at ACL

 

any supporting mods to run stroked and bored?

 

Lets just back track a minute - First you need to find a car and I would suggest buying one with NO (read here not much) rust. It does not matter how well the car has been looked after there WILL almost certainly be some rust somewhere. Body work on these can be expensive if you can not do it yourself (ie Weld) as all of the new metal will almost certainly need to be custom fabricated.

Then I would suggest before you commence on any modifications you spend a bit of time and money and strip the front and rear ends and freshen them up. unless the car you buy has an impeccable service history ( read $$$$ purchase price) the rear brakes will need to be done at a minimum. The front end bushes and rack bushes will most likely need to be replaced. Its a good chance that you will need to service the cooling system as well.

Ok now you can start to modify it with a reasonable amount of confidence that it will not break and spear you into the scenery.

Supporting mods

You will need to replace the ECU -the off the shelf unit from the UK will buy you a small country town.

My plan is to replace the ECU and upgrade the ignition to distributorless before I pull the motor and modify it internally. I have not decided which ECU I will use there a re a couple I am looking at. The AC Delco from the GM L32 or an aftermarket called Megasquirt are the two candidates. One I have it running well in standard form on the upgraded ECU I will then pull the motor and rebuild it.

 

ok, m90 poser,, what warrjon says is good advice.

lets face facts ,, you dont even have a vehicle to start on, whats with that?

and here you are,not knowing any of the engine facts and info, comon give us a break here.

Nope! somethings aint ever gonna happen.

sorry signing off!!!! JEEZ

 

Ron, quit being a douche. the whole point of this thread was to find the best type of XJS to start off with, get a game plan, and then start the project in the summer.
your advice a couple pages back was great, now please quite $hitting on my thread.

 

on another note, ive seen several performance V12 projects where guys have been running AJ6 heads. arent these heads DOHC? does anyone know anything more about running these heads? is it bolt on, or severe modification?

 

oh, and Warjon. how do you plan on getting an L32 pcm to run your jag? i dont see how thats gonna work.

youd have to add a CPS at minimum. all of the throttle and ignition on the series III are fly by wire and are controlled by the PCM, and i know for a fact that you cant run an L32 pcm on an L67.

 

The heads you mention (AJ26) are V8 so your 4 cylinders down, you must mean AJ6, and yes, very heavy mods, you can cut both timing covers, there's a guy on youtube that's done one and supercharged it, it's not running yet....

If I were you I'd speak to Rob, if you're serious...

Rob Beere Racing: Performance Jaguar Parts

The 6lt JaguarSport unit would be the one to play with. It uses a Zytec ECU.
Another guy who can give you more info on producing serious power out of the V12 is Roger Bywater, he, along with another guy called Ron Beatty actually designed and developed this powerplant at Jaguar.

WELCOME TO AJ6 ENGINEERING / AJ6 Engineering

Ron ran a company called Forward Engineering, he's not with us any more, I had one of his units at 5.7lt that developed a genuine 415bhp, N.A. of course, but tree pulling grunt.

I have a 6.1 block TWR crank, Omega pistons, magnesium twin throttle bodies from an IMSA spec engine, running Tech 3 management, a happy 550bhp. The cam's where from Gran Tourismo Jaguar, but Rob produces similar. It's essentially a US Race spec' TWR unit.

These can be very very expensive to build, unless you're like me, and have plenty of time to devote to getting the engine together.

 

i said in the first line that they were AJ6 heads. and yeah, the one i saw was blown but i saw a video of it running on youtube.

thanks for the links Sean.


ive got a question for you then. those 6 and 12 carb setups that a lot of the performance v12's are running (not the quad carb pre 75') look very interesting. how would one go about obtaining one of these carb setups?

 

We used to look for Weber IDF's off old Fiat's and the like, rejet to 48/50mm. Weber, Solex etc, just twin choke down drafts.

You don't need to blow these units,

Mike Roddy XJS Sports Sedan Burnout - Winton 2007 - YouTube

same unit as mine. I could get more power, but in an E Type road car it wouldn't be of use.