Hi. I hope this is the proper place to ask this question. If not, please accept my apologies.
I am in the USA and I am building a vehicle at home from scratch, frame and body. I have aquired A V-12 Jaguar motor, which I intend to rebuild, and install in the vehicle. It previously had a fire I believe was caused by a fuel rail leak. I'll need to replace some things.
I have located the serial number on the rear of the block, which is 8S19584LB. I know the engine was taken out of a 1978 jaguar xjs. What is confusing me, is that according to the serial number, it is a 5.3L XJ-S v12, and HE, and low compression. Every place I read, HE engines weren't produced until 1981, and had higher compression of 11.5:1 or 12.5:1, and the "LB" prefix designates low compression, at 7.8:1. Also, as I understand, the HE engines had a special swirl type head, which was not released until 1981 or later. On an engine identification program on the net, I get these results....
PREFIX : 8S Jaguar XJ-S 12 5.3L 12 cylinder
SERIAL : 19584 Lucas Digital P fuel injection.
HE (High Efficiency).
Champion BN5 Spark Plugs. Gap .025".
SUFFIX : LB Low Compression with Grade B pistons & liners.
(10.8:1 Compression)
MFG YEAR (GUESS): JUL 1981 to LATER


Is it possible that this engine is original to the 1978, is an "HE", and has 10.5:1 compression? Also, there is another set of numbers stamped above the serial on the block which read "I5 N 77", which I am guessing may be a date code of 15 November 1977.

thankyou in advance for an help any one may offer.

Sam

 

If all the spark plugs are at the same angle( pointing in the same direction twoards the center of the engine as I recall), it's an "HE". If they are at different angles (some pointing forwards and some rearward as I recall) it is pre-HE.

If you know for an absolute fact that the engine is from a '78 it cannot be an HE unless it was swapped out at some point. Even though Jaguar did some strange pre-production things, 1978 and 1981 are just too far apart.

Your engine number info looks like it came from Sean Straw's webpage. He researches stuff carefully so the decoding deserves some credence. So...the mystery thickens.

Is the motor complete will all external bolt-on equipment? If so.....

Is there a square ignition amplifier box bolted to the left intake manifold? If so, it's a pre-1989 HE.

There should be a device on the underside of the throttle turntable. If you can determine this is an on/off switch, it's pre-HE. If it's a rheostat type of thing, it's the throttle position sensor used on the HE engine.

Does it have cold start injectors? If yes, it's early HE or pre-HE. If not, it's late HE.

I almost hate to mention the third possibilty: the interim high compression, non-HE engine used in '80-81. Very desirable variant but still too late to have come from a 1978 car.

Are you *sure* the car was a '78 ? Did you see the car? Or have the VIN?

Sorry for the rambling answer.

Cheers
DD

 

seen the car it came out of...was 1978. rechecked the engine number today, and thought that it may actually be 8S10584LB instead of 8S19584LB. several letters/digits are double stamped or not stamped fully. hard to tell if 4th is "9" or "0". I retried the ID program..(yes, was Sean Straw's site) and got more probable results....
PREFIX : 8S Jaguar XJ-S 12 5.3L 12 cylinder
SERIAL : 10584 Lucas D Jetronic fuel injection.
Champion N10Y Spark Plugs. Gap .035".
SUFFIX : LB Low Compression with Grade B pistons & liners.
(7.8:1 Compression)
MFG YEAR (GUESS): MAY 1978 to OCT 1978

Also, you were absolutely correct about everything you suggested....no ignition amp, was an on/off under the throttle turntable (burned and half melted), cold start injectors, and front 6 plugs face forward, and back 6 point to the back.
Also, I believe with the Lucas Digital, there would have been sensors in the exhaust manifolds, which there were none present.
Thankyou for your help.

Sam

 

Sounds like a pre-HE engine....Lucky you, if true!

When I was at TWR in Oxfordshire (Jaguar's factory racing programme) the pre-HE engine was vastly preferred as it had much better flow rates...
so if you want the best of all worlds, use your pre-HE heads and have pistons made (shouldn't cost more than OE replacements) at about 9.75/1...
tell the piston guy you want the outside edge of the piston to come to the top of the cylinder bore (your old ones don't) with a 'BMW bathtub' in the middle for valve clearance & correct CR...
Shorty tapered gudgeons with double-wound clips if he has them, and teflon buttons on the skirt.

This mod is worth about 75 bhp. + adds 4 mpg.

 

Depending on your application, you might consider using 6 40DCNF Webers rather than having to reconstruct the old VW-hatchback based injection system. Makes the V12 start to sound like a Jaguar again.

(p.s. stock cams only, please)

 

Thankyou for the ideas. I've been tearing it apart today, to see if all is good inside. there's a lot of carbon on the pistons and valves, but that will all come off with a wire brush. The cylinders are good...they don't appear to be scratched, and I can see as you said that the pistons don't come up all the way by the carbon ring at the top. the cam shafts had some water on them, so there was some surface rust, but when I put a wrench on and turned the crank, all the rust wiped off, and the cams appear to be fine.
I am building a car from scratch, with what ever parts I can find, just for a fun project. It may just turn out to be a "Rat Rod" when finished, but I'm having fun doing it, and my nephews are helping me. I won't be racing it, only cruising around town and to car meets for fun. I found this engine last week, and decided that I wanted it immediately!...and I have been reading and learning what I can about it. I want to put a 4-speed overdrive transmission in it, and I was thinking about making a single pass fuel rail for it to replace the double rail that was damaged in the fire. I was also considering converting it back to a carb system instead of the fuel injection.
I'll absolutely look into the suggestions that you made and find out more.
Thank you again for the suggestions.

Sam

 

Can you get all of the traction controls working with that engine?

 

there wont be all the traction controls and all that on my car. It's just a "hotrod" that I'm building at home. If I can find an image hosting service, i will post a couple photos of it. I think the only thing that will be from Jaguar is the engine. I wanted to build something other than a "T-Bucket" or a "32 roadster", and I wanted to build the frame and body and everything myself, instead of buying a kit. I also want to put something different in the car, other than the standard V8s that everyone uses, and found the Jaguar V12.

Sam

 

here is a photo of the car as I have it as of today.
hopefully, it will look a lot nicer when it is finished. There is a Ford 390 engine block sitting in it now, but I plan to remove it and install the Jaguar V12.This is the first time I have tried anything like this, so it isn't real pretty....yet)

Sam

 

I can't get it to show the pictures, so here are the links to them.

sam

http://img832.imageshack.us/i/32676893.jpg
http://img535.imageshack.us/i/97460967.jpg

 

http://img535.imageshack.us/i/97460967.jpg/
http://img832.imageshack.us/i/32676893.jpg/

should work now