Looking for info/advice. As I posted in my intro, I've just been acquainted with this 80 XJS V12. Wondering what it's rarity is. I have some paperwork in the car that has ENG# S17133SB. 326ci. 284hp. 74669 miles on the speedo, and looks to be original as the it matches info on the inspection forms.

 

That may well be one of the rare 10:1 PreHE cars.

They were 1980 till 1981ish just prior to the HE introduction.

They ran a P Digital EFI system, same as the HE.
The normal PreHE ran a Bosch D Jectronic Analogue system.

The ONLY way to really know, and then give an idea of value, would be to request a Certificate from JDHT (Jaguar Daimler Heritage Trust). This will answer, once and for all, the question.

If it turns out to be one of those "rare" cars, it is a treasure in any language.

 

I THINK that -pre-HE P Digital engines came in at engine number 16401.

That would imply that it is a P Digital, albeit what I think is a catalyst US 9.0:1 compression engine rather than the full-fat UK 10:1 engine.

However, it's still the best Auto US pre-HE to have (IMHO!)

Well done!

Paul

 

So I have gotten both sides.. it could be either..so without getting a report from the JDHT (Jaguar Daimler Heritage Trust) I cannot fully be sure what variant engine is in it? Is there a registry that says vin-vin has this.. and vin to vin has this... or is that what the trust has?

 

V12CAT,

There are a number of changes in the engine bay at the introduction of the P-Digital setup. However, one of the big design features was the use of the Lucas 6CU control unit. One of the novel elements was the incorporation of the manifold pressure sensor inside the unit. This meant that a vacuum pipe runs the length of the car to the ecu. So, I think that's the easiest check to understand what engine you have.

As regards a certificate from JDHT, it will give you VIN, engine number, car build date etc. But I'm not sure it will say "P Digital" on it, or the compression ratio etc.

Another reason why I'm pretty sure is because you have paperwork that says it's a 284bhp engine. I thought even the US catalyst P Digital was only about 262bhp. So your paperwork seems to imply it's closer to the UK power output of 300+bhp. (I've even seen a figure of 313bhp quoted for the UK engine.).

Cheers

Paul

 

Ok, thanks. This is what I was going off of.

 

Ah, I see, the engine info was just hand-written on the license doc by someone. I thought it might be something printed from Jaguar. I wonder where that power figure comes from?

As you've probably realised, that handwritten engine number seems wrong. If you check it against the actual engine, I think you'll find it reads 8S17133SB the SB indicating Standard Compression with Grade B pistons

Paul

 

Ok, I will have to search for that engine number... if it starts with the SB as you stated, I found this earlier today, showing that SB is the preHE engine... so is there a preHE 9:1 and 10:1?

 

Ok, I will have to search for that engine number... if it starts with the info you stated, I found this earlier today, showing that SB is the preHE engine... so is there a preHE 9:1 and 10:1?

 

The early pre-HE engines for the XJS were [something like] 7.8 to 1 (USA cars and perhaps some others) and 9.0 to 1 (UK and most other markets). These were rated at 244hp SAE net and 272hp SAE net...although these numbers can vary a bit from source to source.

The short production hot rod pre-HE, which I think you have, was 9.0 to 1 (USA) and 10.0 to 1 (most others). These were rated at 262hp SAE net and 300hp SAE net respectively. As it happens, the low compression version of the HE V12 was also rated at 262hp. The 284hp rating written and mentioned is not typical....or at least not familiar to me.

Cheers
DD

 

My suggestion, and will cost you nothing.

Look at the balance pipe, thats the 1" pipe running across between the 2 Inlet manifolds at the rear.

MIDWAY, on the underside there MAY be a 3/8" take off spigot, and I stress MAYBE.

If it has this spigot, it has the 6CU P Digital EFI unit in the boot, and is one of the "special" cars.

It there is NO spigot, it has the 3CU D Jetronic ECU and is a standard PreHE vehicle.

2ND free look.

Locate the ECU in the boot, tucked up in the RH buttress. Look at the side of the casing, if there is a VAC hose attached, it is a 6CU P Digital ECU.
If NO vac hose, it is a 3CU D Jetronic.

That will answer the yes/no of a "hot rod" spec car.

As to comp ratios, USA cars, as Doug stated, were 9:1, the ROW were 10:1, and that was due to emission requirements and fuel quality at that time in the USA.