Jag XJ13

[Mike Blair]

Hi Chuck
I have not gotten a completion date from Fran yet but it should be fairly soon. I am not a mechanic but I have a pretty good knowledge of the Jag V12. I have been a big Jaguar fan for 30 years and currently have 3 Jaguar V12 cars. Of course I also have a V12 sitting in the garage but doesn't eveyone?
The engine headed for the XJ13 was built by a well known V12 guy and is overkill for a street car but I am trying to do it right. It is a 6.8 liter/416 cid (stroked and overbored) 13:1 comp with some extensive head work but designed to run on pump gas. It is waiting for a set of intakes and 6 TMW twin throttle bodies. When they come in I plan to send the engine up to Fran to set in the car so he can make me a set of headers that will fit the car properly. Plan is to use a G50 transaxel. Fran has done some replica wheels (not cheap but essential I think).
BTW a few things I would suggest if you are considering building one. First is go fuel injection all the way. Early V12's used 4 stromberg carbs and this was a compromise as Jag planned FI but could not get the system reliable in 1971. After 75 all V12's were FI and you can get a Jag V12 FI motor with ECU etc very cheap probably less than one with carbs. 6 Webers are an option but expensive and if going that route might as well use the FI twin trottle bodies ie TMW. The best bang for the buck is a 5.3 liter HE FI V12. About 300 HP (350 with rebuild) and plenty of torque and and will easily rev to 7000 rpm (8000 rpm is probably even safe for short bursts)
The cabin has more room than the original which had cooling pipes in the cabin but the car is very low at 39" to top of windscreen. Headroom is obviously unlimited but if you are over 5'10" your head will probably extend above the windshield. (I am luckily short 5'7")
Look for more info when I can get around to my build blog.

 

[Randy V]

It is a 6.8 liter/416 cid (stroked and overbored) 13:1 comp with some extensive head work but designed to run on pump gas.

At 13:1 compression - I hope your fuel pump dispenses 110 octane gas or E85.

But it sure sounds good!!!

 

[Mike Blair]

Yes good point! My engine uses the HE (May heads, fireball heads) heads which will allow a higher compression with pump fuel. The design incorporated a recessed exhaust valve where the sparkplug is also located. This provides better combustion characteristics and better economy but at a cost (see below). Jaguar actually built HE engines with up to 14:1 compression but was concerned about fuel quality in some of its markets (including the USA) and ultimately settled on 11:1 for the production HE motors. Most race type Jag V12's use flat heads (this was used on all the pre 1981 V12s) as that allows the best breathing for high HP engines (600-700 HP) but they are suseptable to detonation at higher compression ratios and require 110 octane. US spec flat head engines were 9:1 but some euro spec ones were 10:1 and those are considered the hot ones. The general consensus has been that the HE heads limit HP to around 400 HP because of the smaller valves. To achieve more than 400 HP requires some special head work (lots of labor). Some time around 1993 Jaguar increaed the displacement of the V12 from 5.3 liters to 6 liters by stroking the engine. My engine started as one of these 6 liter motors. With the increased displacement and compression plus the head work I am hoping to get close to 500 HP and more torque than I might want on pump gas. That is with the TMW intake system of course. Should be just enough in a car that is in the 2300-2400 lb range but we shall see.
I really think one of the most important characteristics of this car is the song that it sings:laugh:

 

[Chuck]

For fans of the XJ13, the current issue of Motor Trend Classic is a must read. The cover story is all about the XJ13 with an excellent write up and a host of very good pictures.

 

[Neville]

If any of you are interested in seeing the oily bits of a Jaguar quad-cam prototype V12 I have posted some pics here XJ13 - Building the Legend

 

[Chuck]

Neville

Thanks for the link. I visit your site often. You are doing an amazing build and creating a great historical record.

 

[Chuck]

The twins have arrived.

 

[Neville]

The twins have arrived.

Congratulations :thumbsup:

Do they have names yet? What will they be when they grow up?

 

[Mike Blair]

The twins have arrived.

Very nice! Chuck are you still considering using flat heads or sticking witth the HE heads. I believe the HE heads are better for a road car where the flat heads are better for a falt out race engine. You may want to talk to Chad Bolles about how the engine is going to be built up.

 

[Chuck]

Congratulations :thumbsup:

Do they have names yet? What will they be when they grow up?

The youngest twin is named Rusty. He has a great future as a coffee table, a la Top Gear. Jeremy Clarkson will be proud.

The older twin has not been named, but we think he may have a future either as a power plant for an XJ13. Or a coffee table. At this age it is hard to know.

 

[Nick]

Hi Chuck,

Hope you don't mind I thought you might be interested in these pictures I took at the Cholmondeley pageant of power in 2008.

 

[Mike Blair]

Hi Chuck,

Hope you don't mind I thought you might be interested in these pictures I took at the Cholmondeley pageant of power in 2008.

Yep looks like THE original!!
Odd, I have never seen it with numbers slapped on.

 

[Jim Rosenthal]

There aren't many cars that can compete for looks right next to a real GT40. You're looking at one of the very few. That car is GORGEOUS.....don't tempt me...

 

[Neville]

XJ13 meets GT40 ...

I thought you GT40-types might be interested in seeing the rear suspension setup of the XJ13 replica built by Bryan Wingfield for the late Walter Hill. See any similarities with the GT40? (the setup is very different to the original XJ13 by the way).

 

[Jim Rosenthal]

What kind of transaxle did the original XJ13 have, and what are modern replicas using?

 

[Seymour Snerd]

What kind of transaxle did the original XJ13 have, and what are modern replicas using?

My reading, mostly on The Jaguar XJ13 from XJ-13.Co.Uk - the story of an iconic legend! Peter Wilson's new XJ13 Book plus canvases plus the Jaguar C-X75 - based on the XJ13 - 'XJ13, Possibly the most beautiful Jaguar ever made' - Ian Callum, says ZF, just like us. In fact one of the replicas used the back end of GT40 chassis (not an original, I assume). Maybe that's it above. The site above lists them all.

 

[Neville]

The "original" XJ13 used a DS25 series 1 ZF transaxle. Replicas built since then, using the ZF transaxle, tend to use the later series transaxles - series 2 onwards.

My own replica (documented on Jaguar XJ13 | Building the Legend ) uses a series 1 ZF as original (with the correct ratios). I was lucky enough to find an original "new old stock" S1 ZF still in its original crate since the late 1960s - it was in Utah - isn't eBay wonderful :thumbsup: The owner bought two for his Pantera but didn't need one of them. The box arrived last week and has now gone to be modified (as Jaguar did themselves - according to original documents) with uprated driveshafts.

Most other replicas use the Porsche (G50?) transaxle but I know of one in the UK that has a Hewland box (replica built by Rod Jolley). These, as well as the ZF Series 2 box, may not be "as original" but this perhaps isn't too much of an issue because very few current replicas bear close comparison with the original XJ13 anyway!:uneasy:

 

[Neville]

My reading, mostly on The Jaguar XJ13 from XJ-13.Co.Uk - the story of an iconic legend! Peter Wilson's new XJ13 Book plus canvases plus the Jaguar C-X75 - based on the XJ13 - 'XJ13, Possibly the most beautiful Jaguar ever made' - Ian Callum, says ZF, just like us. In fact one of the replicas used the back end of GT40 chassis (not an original, I assume). Maybe that's it above. The site above lists them all.

The pictures of the quad-cam engine on this site are of my engine (a couple of pages of the forthcoming book are shown as a preview)

 

[Neville]

Yep looks like THE original!!
Odd, I have never seen it with numbers slapped on.

Hi Chuck,

Hope you don't mind I thought you might be interested in these pictures I took at the Cholmondeley pageant of power in 2008.

Mike, as always, is absolutely correct - it IS the original.

Nick - will you be visiting Cholmondeley this July? I have a friend outside Warrington and I thought it would be a good chance to visit him and the pageant at the same time. There's a good chance Jag Heritage will be there again with some of their cars. I thought it would be a good chance to eye up the "XJ13 competition" in the shape of some GT40s :nice:

 

[Nick]

Mike, as always, is absolutely correct - it IS the original.

Nick - will you be visiting Cholmondeley this July? I have a friend outside Warrington and I thought it would be a good chance to visit him and the pageant at the same time. There's a good chance Jag Heritage will be there again with some of their cars. I thought it would be a good chance to eye up the "XJ13 competition" in the shape of some GT40s :nice:

Neville,

Didn't make it last year and have managed to book the Sunday off at work so all being well I will be there. Hope Jaguar make it with the XJ13, it is some car, they always seem to have an eclectic mix of cars