Leaping Jaguar

Exhaust

While trawling around Stoneleigh Jaguar Spares Fair, I came across a set of racing exhaust manifolds from a crashed XJS V12, quite nicely done.
I did speak with my father, sadly deceased few years ago, if we could reproduce another 6 sets to sale for fellow V12 enthusiast. A mould or gabarit as we call in mainland Europe was produced and the set you see here is one of my father's efforts.

I was quite sceptical about fitting such a bulky system in a tightly packed engine bay but everything went smoothly although the handbrake cable had to be repositioned slightly to the side. The power steering pipes sit way to close for comfort and the starter motor also has a very hard life. In the end, I've asked one of my relative to sew some protective boots for the pipes and a thermal blanket with Velcro for the starter motor, done with the same high quality heat proof aluminized mat as I employed in other areas in the car such as centre console, foot wells, fuel pipes, wiring and bulkhead and silencers heat shields.

It features 38mm primary pipes and 44 secondary pipes with front pipes and replacement middle silencer boxes straight through pipes of 90mm, all made in high quality 304 Stainless Steel, 1.5mm thick. Because of the engine bay being so tight, it was not possible to accommodate an equal length primary pipes system without seriously modifying the bodywork so this was the best compromise. In effect, different lengths can be beneficial in creating different sound wave pressures, aiding neighbouring cylinders scavenge the exhaust flow, which is the reason the system is split in four sections, three cylinders each. Flanges are laser cut in a sturdy 304 Stainless Steel 10mm thick plate.

It certainly offers much increased capacity to evacuate burned gases in comparison with the original, block hugger, cast iron arrangement. This set up is essential if you are running with modified cams, plenum chamber, and injection and so on in pursuit of more performance. More power equates more fuel and more air which signifies for burned gases which have to be scavenged efficiently to avoid reverse flow and therefore crippling combustion chamber fresh mix filling.

Straight through 304 Stainless Steel middle silencers replacement pipes were bought from AJ6 engineering, reputedly increasing power by approximately 20BHP, rear =silencer are original Jaguar Stainless Steel items (I believe in 316 grade) from a XJ12 SIII, bought from JagShop at a very competitive price.

Jorge Maia, my mechanic, insisted in wrapping the exhaust manifolds in a special thermal insulating tape, only to discover he was allergic to fibreglass fluff! Notwithstanding, he came through and what a sterling job he did. Thanks Jorge, I owe another one!

The original heat shield that protect the carburettors were sandblasted, zinc plated and powder coated in a not very attractive grey but close enough to the original finish. I did remove it later to apply ton my XJ12 SII as I'll be fitting throttle bodies to this engine and I love the look of the wrapped manifolds.

The sound that the system emanates is absolutely gorgeous, reminds me of a Fifties power boat with its in board V8. It produces a deep, bass baritone drum at idle to a truly ferocious growl a 5000rpm (I didn't dare yet to run at 7000rpm, still need to run in).

Although I do like very much to listen to the engine sound from outside, which is not that preposterous, but I do mind intruding the cabin. I did go to great lengths to isolate the cabin with extra sound proof hardura material, thick sound proofing dense sponge with a lead barrier between the layers and that terrific heat proof mat, that I applied to all foot wells carpets, trim panels, centre console, dashboard etc.

I do remember boiling in my car in the summer, it felt like a sauna and I had few passengers actually feeling sick, so now, I had to take these extreme measures as I ditched the useless A/C (GM Frigidaire) unit in my perpetual chase for more power.

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