A friend has just dismantled inlet side of his engine & we noticed water rail has a section which has clearly had an indented flat area very professionally welded in near the hose attachment. My own XJR has the same & it appears to be there to allow clearance for a part of the throttle body (Perhaps the TPS)
Photo from E Bay listing shows the exact water rail.
However latest Jaguar Classic Parts clearly shows water rail without this indent.
My research indicates water rail originally had part no EBC10342 which is now unavailable, obviously replaced by NBD2226BA which clearly looks the same but I suspect could be thinner to fit the XJR requirement.
Other pictures I have of the inlet side of X300 engines clearly show the rounded style with no indent.
Other than the E Bay photo my friend passed on to me I could locate no other photos showing this indent.
Could Jaguar been using up the original design by suitably modifying them in production prior to the introduction of the redesigned part NBD2226BA.
The XJR parts manual shows part EBC10342 for the 3.2L engine & NBD2226BA for the 4.0L & supercharged engine.
I look more comments from our more learned members.

John Herbert
(1996 XJR, previously 1982 XJ-S & XJ6 Series 111)

 

Using up a supply earlier design parts is very plausible.

Going thru the effort of *modifying* a supply of earlier design parts does not seem plausible. Not in modern times on a mass produced vehicle....and not with something like a water rail.


I consider parts illustrations to be rather generic in most cases. I'm not surprised if such illustrations do not show the design evolution of any given part.

All just "IMO". Not "learned"

Cheers
DD

 

Doug, I have attached photo from my files of rounded style as depicted in parts diagrams so I do believe this is how the latest part is manufactured.

John Herbert

 

I've never seen an XJR engine that didn't have the modified water rail. I can't image the throttle potentiometer would fit if the unmodified rail was used. That was why the modification was implemented in the first place. I assume Jaguar decided it was more cost effective to modified the parts than to pay for dedicated sand cast tooling. The unmodified tooling was die-cast, but this process could not be used to make the modified shape. Sand cast parts are more expensive than die-cast, so this would help offset the cost of modifying die-cast parts.

 

Thanks, but that is a photo of a normally aspirated engine, which uses the rounded pipe. Per the original post and Andy's comments below, the XJR needs the indented version.

eBay is probably a good source if you keep your eyes open.

.

 

It appears XJRengineer is in agreement with thoughts in my original post, they were using original part EBC10342 suitably modified as he points out, however once redesigned part NBD2226BA was introduced I do believe it was designed with the required indent for the XJR in mind - Parts manual states new part fits all x300 & specifically mentions supercharged model.
I believe the newer part is actually thinner in the required place & a comparison between the old part EBC10342 & NBD2226BA would be the only conclusive outcome.
Yes Al I was aware that photo was of unsupercharged engine, it was merely posted to give view of the new part which I do think appears thinner at the end adjacent to the hose connection.

John Herbert

 

Further research has turned up the following dimensions -

EBC10342 - 34.4 x 8.5 x 4.7 cm

NBD2226BA - 34.5 x 8 x 4.5 cm

It does appear the later part is slightly slimmer, hence slight extra clearance required by XJR & as previously mentioned later part is listed to suit XJR.
Whilst XJRengineer has not sighted one without the indented water rail, surely someone out there has replaced their water rail, perhaps with the newer part.

John Herbert