XK120 exhaust silencer thoughts

I wondered if I could call upon the great wisdom of this forum to offer some measured thoughts on a single-pipe s/s exhaust system I’ve just acquired, please.

A peep down the silencer shows a solid baffle less than 180mm from the inlet pipe entrance with hardly any perforations (maybe 6 rows) ahead of it to allow re-routing of gases. I worry that back pressure could significantly impede airflow and inhibit performance. Not that the car sees anything beyond spirited road use. The vendor (a prominent international supplier of parts for British classics) assures me that this silencing arrangement is completely normal. It just doesn’t seem quite right to my untrained eye, so before I fit it, does anybody have any thoughts please?

BTW I know many on here endorse mild steel systems, but a quote I received from a recommended vendor was more than 3 times the cost of this and I just couldn’t justify it.

Chris Tunnicliffe

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Based on input from some Forum members I investigated the subject some years ago and wrote an article on the subject.
Basically there are two types of Jaguar dampers: (1) the “straight through” type and (2) the “baffle” type, the latter the most commonly used version on Jaguars. The “straight through” type (a Burgess invention) in its original construction was only used on some pre-war sports cars, but in a modified form also on the XK 120 (OTS) SE versions with “twin pipe” racing exhaust C.5700.
All other Jaguars used the baffled type.
Attached see photos of an original Burgess and Harmo silencer with the flow of the exhaust gasses shown on the outside. The only difference between the two brands being the position of the baffle plates.
The only difference with your stainless version I can see is the length of the perforation: both Jaguar silencers have internal pipes made from perforated steel, meaning perforations over (almost) their entire length, thus reducing the back-pressure. Hope this info helps.

Bob K.

Thanks very much Bob. Appreciated. My real concern is the position of that first baffle. If it was a reasonable distance down the silencer (even like the Harmo) I wouldn’t be worrying, but it’s positioned with only about 2” of perforations before that solid blockage. I did wonder if I could run the silencer backwards so the baffle is at the tail end, but the feed & exit pipes are differently angled and the gases still have to escape. Or is it a non-issue? Cheers!

Chris T.


I guess the back-pressure with such a short length (2") of perforations will be higher (if compared to the silencers having internal tubes made from (fully) perforated material). Cannot judge the impact on the power output, but at the same time the question is whether you want to go racing or just a nice touring car… In any case yours might be less loud than the original versions!

Bob K.

Thanks again Bob. I remain uneasy about it but I’ll fit it and see how it performs. If it has a noticeable negative effect on performance I’ll drill some holes in the baffle. I’ll report back in due course. Not sure I’ll have time to attempt a fit before Goodwood Revival though. Cheers!
Chris T.