Removing the emissons control system

[kpytoi1]

On a 1968, US ZenithStromberg car - there's an emissions control unit going from the rear exhaust manifold over the engine and back into the carbs. When installing an aftermarket exhaust system with new headers, how does one eliminate the issue of the emissions control unit? Can you simply unbolot the harware and bolt up/seal the opening where the gases get introduced back into the intake? Does the removal of this mess affect the tune of the car, or are there any other considerations one has to make before just taking off this system, like sensors or wires, etc. - Thank you for your help.

[andy303]

There would be no harm in removing the cross over and installing the shaped cover used on the later S2 federalized engines, like mine (see my xkedata page, link below) or make your own blanking plate to cover the opening on the intake manifold. Just be sure that the gasket is well sealed. While you are at it, you may also wish to remove the secondary throttles.
The functioning of the system is explained in both the Bentley reprint and the Haynes manual, so I won't repeat it here. You can either leave the secondary spindles and linkage in place (I did) or you can plug the holes in the manifold.

Here is a link to a discussion about the duplex manifold from the jag-lovers forum that I started last year, with some pictures: http://forums.jag-lovers.org/av.php?1452615m18

Removing the secondary throttle plates or "butterflies" is a fairly common discussion on jag-lovers, as one might expect. Plenty to search for there.

Consider using the cast iron exhaust manifolds instead of the headers. In you case you just need to replace the rear one. They really work better on a street driven car, are quieter and emit less heat than tube headers. Check the poll that Heuer has in the "Updates" section.

BTW there are no sensors or wires. You may need to tweak the carbs after removing the secondary throttle plates. And without the cross over you may need to keep the engine on the lowest choke setting for a tad longer until the engine is warm.