It is hard to find headers for our Jaguars. A U.K. company called “Bad Cat” offers “shorty” headers for close to $3000. I have not found any others for Jaguars. Manufacturers have been placing catalytic converters as close to the exhaust manifold as possible. This is purely for emission purposes. The emission testing labs report that in the testing cycle about 50% of total emissions occur during the open-loop warm-up period. Placing the cats closer to exhaust manifold decreases cat “light-up” time; thus shortening the warm-up period. California is very aggressive on emissions, and does not permit any modifications of the cats and forward. I don’t know if they exempt shorty headers.

Other jurisdictions do not test emissions or just confine testing to a “sniff test” of fully warmed closed-loop exhausts. For owners in these jurisdictions longer tube headers may be a possibility.

Years ago I was an early adopter of long-tube headers for my ’05 Cadillac CTS-V. The manufacturer was a close friend. The original development cost was about $2500 for the first header set. He marketed the subsequent headers at about $1200. Total production for this CTS-V particular edition was about 4000 vehicles. Friend figured maybe 1% might be interested, so he did a production run of 25, which took several years to sell. He also made Corvette headers, and sold many more of these headers. Years later, he subcontracted assembly to American Racing Headers using his proprietary jigs. Aston Martin uses the same basic engine block and heads for their V-8 Vantage. Aston Martin hand assembles their V-8s in Germany, using different crankshaft, rods and pistons. I cannot find the specifics of Aston Martin modifications, but I think the cylinder bore spacing and exhaust ports remain about the same. Both the 4.2 Jaguar and Aston Martin have rectangular-shaped exhaust ports. Not sure about the 5.0 Jaguar – it may have round ports. Several companies sell headers for Aston Martin Vantage V8s. Aston Martin’s production numbers are much less than Jaguars XK/XKR, which tells me that the market for Aston Martin mods is at best very small.

Here is an informal list of some sellers:

1. An example of Aston Martin OEM exhaust manifold:

https://www.ebay.com/i/263865332166?...3D263865332166.

1. Pure Performance, located in London, sells long-tube headers to USA for $1675, free shipping. These headers are made by “Top Gear”. https://www.ebay.com/itm/Aston-Marti...FGiI#vi-ilComp
2. Top Gear USA is actually located in U.K. They advertise the headers at $1881.61 and claim to have 19 sets in stock. https://www.topgear-usa.net/aston-ma...ifolds-headers.
3. Scuderia Car Parts markets a shorty header:

https://www.scuderiacarparts.com/aft...-2005-on_14812.

Top Gear USA is located at:

• Topgear USA, Top Gear (Bridport) Ltd.
  Unit 1 Gore Cross Business Park
  Bridport
  Dorset
  DT6 3UX
  VAT Number: 429 0781 40
• 01308 427588
• Fax: +44 1308 459 108

Top Gear appears to be a manufacturer for several vendors. Top Gear markets a large number of exhaust systems for limited production autos. Whether or not a Top Gear Aston Martin header will fit our Jaguars exactly is an open question. My guess is that it will be close – perhaps exhaust ports will match, but there may be some minor clearance issues around steering column. Maybe Top Gear will work with Jaguar owners. No doubt the market is greater for Jaguar than Aston Martin.

 

Frickin Jag (forum member) has made some headers, but I don't know how far he has taken it.

 

Might look at https://www.jaguarforums.com/forum/j...ifolds-203415/