Exhaust Silencers?

[mike smith]

Evening Gary
   Nobody has any idea what they are for!!
   Mike Berrisford and myself have had a batch of manifold plates made up to make a free flow down pipe instead of the cast iron manifold and steel flexi one
   I think I also have a starting handle if you are still looking for one
   Mike Smith

[GSouthee]

Hi Mike
   
   That sounds interesting, was thinking of similar lines re manifold plates but looking in engine bay not much room for free flow down pipes. Would be nice to pic of item and pipes. Will PM you re this and the starting handle.
   
   Cheers  Gary

[ACOCArch]

The idea was originally patented by William Hurlock and AC (Acedes) Cars in 1936/37. The patent number is GB470786A - Auxiliary Silencers. Details of the patent can be found through the UK Patent Office search engine espacenet.
   I imagine the boxes helped damp out noisy resonant frequencies. Whether the theory outlined in the patent would stand up to scrutiny against the current understanding of resonance in exhaust systems is doubtful.
   As the boxes are branches off the exhaust system, rather than through boxes, it seems unlikely they would cause any resistance in the system. However, resonance in both intake and exhaust systems can aid, or hinder, the fluid flow rates. The impact these boxes have in that respect are not known to me.
   In the 1950s, on our family Two-Litre, my father replaced the two auxiliary silencers with smaller diameter tubes of the same length as the originals. I can't recall if it made any difference but the replacement items were made of power station boiler tubing and lasted much longer!!
   I have a vague recollection of replacements being made to original drawings about 15 years ago. Brian Eacott may be able to help.

[GSouthee]

Many thanks for info, however I am looking to improve the flow of the exhaust system. I have a couple of spare aux silencers on my shelf and a couple of original manifolds (one having been smoothed over to improve look), was going to use one to make a manifold flange but looks like mike may have already saved me the hassle.
   
   As to the flow/pulse of the gasses I think the gasses exploding sideways and pulsing back so closed to what is a fairly restrictive manifold anyway does not help with free flowing exhaust. AC Aces use a free flow manifold which certainly improved performance in this respect.
   
   This is a route that I will look at going if I can workout where to fit the down pipes in as the engine bay/ steering column is a bit tight for space. I believe that some owners have fitted them through the inner wing and run the pipe under the cat from there. Will need to research this.
   
   Cheers  Gary