I have been working on my 1988 XJS. Currently have the motor out for a re-seal and engine compartment detailing. The car had several performance modifications done by the previous owner which I am learning about as I go. With that said, I am trying to identify the intake manifold and throttle body. It was my understanding that the 1988 V12 manifold would have the ribbed surface. However, mine has the Jaguar V12 motif. See photo. Also, I read an article by aj6 engineering that mentioned modifying the intake by adding bellmouth extensions and using a larger throttle body. Is this what I have here?

Pay no attention to the sand inside of the manifold in the photo. I took it right after pulling it out of the blast cabinet.

 

One more thought - the car had the air pump disconnected and I don’t see any holes in the intake manifold for the air rail.

 

Its had a manifold swap, makes sense, the air pump was a fiasco at the start/

Remove all the junk, easy and steady as you go.
Engine being OUT, the delivery pipe under the exhaust manifold will basically fall out.

Inlet work as you mentioned, your car, your wallet, your choice.

I looked at that waaaay back, and never went for it.

16CU EFI magic box, larger throttle discs (guy with a lathe that actually knew how to use it did the machining), over run valves removed , ONE vac hose, A Bank underside vac port to the vac capsule.

They all went like stink, and that was good enough for me.

 

Sure looks that way.

I suppose other outfits besides AJ6 may have been doing similar mods....but I doubt it.

Cheers
DD

 

That manifold is intriguing because it's an early manifold with the webbing casting between the tracts but with apparently a later collection casting with the inset V12 badge. And then I found this from Roger Bywater of AJ6 engineering 19 years ago....


.I think I can safely say that we have seen the insides of more V12
inlet manifolds than anybody anywhere.

All V12 EFI inlet manifolds are fundamentally the same internally
although there are wide variations in tract sizes between
individual examples because of pattern and shrinkage variations.
There are also variables with regard to pipe connections and
injector mountings according to year and market. There is no
inherent performance difference between 5.3 and 6 litre types.

There are no factory manifolds remotely resembling the changes we
make for our Plus Torque kits which are good enough for around 450
b.h.p. when combined with the right engine mods.

In the course of remanufacture we can, as an extra option, convert
the early ribbed top manifolds to the same picture frame for
the ‘V12 Jaguar’ badges exactly as on all post facelift cars so
they do then look very like the 6 litre type.

All production throttles are the same size but there are lots of
variations with regard to vacuum tappings and so on.

So it's very possibly one from AJ6 that's been split and re-welded with the extended inlet tracts.

Paul

 

Thanks for the replys. The person I bought the car from was performance minded so, as I said, I am finding there wow some interesting modifications made that I was unaware of. I consider this a bonus because I have always modified my cars for better handling and performance.

Can someone tell me how to determine if the throttle body has been upgraded too? I provided a picture showing the bore size.

Also, one of my main goals is to make the top of the motor look as clean and organized as possible. Has anyone found a way to organize/run the spark plug wires so it doesn’t look like a pile of spaghetti?

I am greatful for your thoughts!

 

I made the swap myself, not for any “performance gain” but to minimize the grinding needed to smooth everything out so I can polish it. That’s a few hours of really simple work to have a really shiny bit.
I’d like to do the same with the valve covers except they are the very, very, rare early cover with the word JAGUAR actually cast in instead of a decal on top of the flat spot. Without those I’d grind the valve cover smooth and polish them. ( I may still do a set just to see which I like the look of )
I intend to polish as much of the top of the engine as I can. Just like the XKE was done.

With regard the plug wires? Why not eliminate the distributor and plug wires completely?
Coil over plug and a aftermarket ECU will allow you to do that. Bundle the thin trigger wires together in one run on each side going to the front. You can include that bundle of wires with the trigger wires for the injectors.
You will have to deal with the cruise control bellows if you intend to keep it operational. As a racer we just eliminate that with the attending hoses.
I assume you have either disposed of the A/C compressor or moved it off to the side?

 

That is an AJ6 Engineering modified manifold. It will therefore also have the AJ6 Engineering modified ECU and large throttle bodies, which are a prerequisite for the manifold mods.
This is confirmed by your measurements. The standard throttle body diameter is 63mm (2.486inches). your measurement shows 2.8+ inches = 72mm.
https://aj6engineering.co.uk/cost-ef...he-jaguar-v12/

 

Lucky you to have AJ6 engineering intakes! Very expensive when they were still available.

If this car was running when you got it, slap it all back together and enjoy. If it was not running, consider a Mobeck kit. The AJ6 kit was based on modifying a 1980’s ECU which is somewhat limiting… but Mobeck uses MaxxECU …. Could tune it any way you want.

Most new cars have plastic intake runners. I wonder if some bright spark could use the AJ6 design as a basis for plastic XJS intake runners. 3D printing is based on the deposition of melted plastic, so heat could be an issue . I’m not retired so that bright spark is not me.

 

I like the coil over plug idea! I believe Mobec offers this, correct?

The cruise control was removed before I got the car. I am doing a Simply Performance manual swap as part of my project so it wouldn’t be needed anyway.

The A/C compressor is another thing. I have been researching moving the compressor down to where the air pump was and running custom lines in an effort to conceal as much of the system as possible. The bracketry looks like it could be a little tricky though.