V12 - removing unneeded emissions hardware

Over the winter, I have rebuilt both heads on my 73 OTS V12 and are now reassembling the engine. My builder suggested leaving off various components related to the ugly pollution control piping and hoses that are not really necessary, and are negatively impacting performance. He mentioned a “blower” and its hoses.

Does anyone have experience with this? Are there concerns or unintended consequences to be considered?

I did the same on my V12 import from USA.
Easy to do…no consequences to be concerned about (when compared to what was produced for the UK market at the time.





Anything that is plumbed into the exhaust to change the exhaust gas composition can be considered emissions equipment.

1/ There is an air pump sitting under the right hand front edge of the car. This feeds a set of air rails which look to be connected to the inlet manifolds, but closer inspection shows they connect to the exhaust ports. The purpose of these is to blow air into the exhaust to help combust nitrous oxide molecules to something less harmful. Subject to your local MOT regulations, the air pump and air rails can go, but you’ll have to plug the twelve holes on the inlet manifolds.

2/ There also may be exhaust gas recirculation from the headers back to the tops of the carburettors - you can plug those.

3/ The vacuum hoses can be simplified to be like the last page of the Parts Manual rather than the thermo switch etc controlling vacuum retard at the distributor.

Lower priority items are:-

4/ If you drill a vent hole in the petrol cap, then the carbon cannister and its plumbing can go. The fuel tank small pipes need to be plugged and the fuel evaporation pot on the inside of the left rear fender can go.

5/ The Stromberg bypass valves can be blanked off. This only affects carburettor air mixture at overrun, but a brittle bypass diaphragm or leaking vacuum connections mean it can have an effect all of the time.

6/ Ditto for the Gulp valve.

Purchase a copy of the tan coloured Owners Manual to see the difference in UK and US spec. The 1974 Parts Manual shows all of the relevant items.

See https://www.jag-lovers.org/snaps/snap_view.php3?id=1190800376

kind regards
Marek

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As always, great recap Marek. When I restored my V12 several years ago, I did most of the items above. Really cleans up the engine. JS

There are several easy techniques covered in older threads here on how to plug the exhaust manifold holes, none of them hard and all seem to work. I just refreshed my entire V-12 engine and did away with the air pump, which was already non-functional anyhow, the exhaust gas recirculation, the vacuum retard (1-3 in Marek’s post), and the gulp valve.

Marek - Very helpful as always. I really appreciate your #4, which I had missed before.

The last page of my parts manual (February 1974) covers the electrical aerial.

Can you provide a page reference for the referred mod? Page 25.18 covers the thermostat system but doesn’t mention the small next of vacuum lines

I am gonna do just as you described – if I understand it correctly – by sourcing on original style thermo coupling


it correctly

…the last page of the vacuum diagrams as per the hyperlink to the annotated pages of the manual originally posted back in 2007.

The last version has the distributor retard temperature connected to bottom lower left carburettor port, rather than via the cocktail of choices.

kind regards
Marek