Bob..... when you get the chance, I wonder if you could do me the favour of removing your air cleaner (it should come off once the single butterfly nut is undone) and look on the body of your carburettor for an ID number. It may be in two places, firstly possibly on a triangular tag, but secondly and always at the base, front left side, facing forwards. There should be 4 digits followed by an S. I would be very interested to find what carb is on your engine.

Please also note that I posted a rely to you on the previous page.

Thanks Bryn. All very interesting stuff. I am in London today, watching England being outplayed by New Zealand in the cricket match at Lord's.
I will check the carburettor number when I get back.
the manifolds you sent links for certainly look more like mine. I'll follow them up later too.
Thanks again
Bob

I think the driver side manifold has a central exit and the passenger side one has has a rear exit - and I think that was the case for the 407-410?

Bryn

There is no number on either of the places shown in your diagram but there is a number stamped on the left hand side leg as you look at it from the front of the car - that is the other side from where your diagram shows it to be. Unfortunately this is somewhat obscured by a clamp holding a rubber pipe and I do not have the means to remove it at the moment. The number starts E7A 32.... but I can't see the rest of it.


I have tried to attach a photo.

Is this of any use?

Bob

That is certainly the case on my 410 Giles.

410 Exhaust Manifold
 

The manifolds on my 409 (with PAS) are the same, LHS has rear exit and RHS has central exit, and I recall seeing the same on other Bristols of the similar period. The RHS manifold has the central exit and the valve controlled by a bi-metallic strip which forces exhaust gas back across the inlet manifold to warm it up quickly from cold. All evidence, cars, and reports I have ever seen would say that all the Bristol 'Poly' engines had these features and the 4-barrel Carter carburettors, when they were built. In a comprehensive history of car engine design, I think the Poly engines would deserve an honourable mention for the good port and combustion chamber shapes allowed by the valve layout, without incurring the complication of the 'Hemi' double rocker shaft arrangement. It really is remarkable for a single cam 'V' engine.