On trying to assemble a complete engine and bits for my Series4, I notice that the inlet manifold is water heated. Is this a good thing? I've always strived to make the inlet air as cool as possible for performance. After all, installing an intercooler after a turbo adds horsepower on all cars. Would it aid horsepower if I disconnected the water pipes, and by passed the manifold?
a lot of owners of Sunbeam Alpines Series 4, which have exactly the same manifold, have deleted the warm water arrangement. This was perhaps a good idea for regions like northern Scandinavia, but in the UK this system is only a disadvantage. After all on series 5 alpines you don't see either a warm water arrangement. On my Rapier series 4 I have installed the so called Webcon conversion which makes it a totally different car. This conversion does not include a warm water arrangement and exactly for the reason you mention the air for the carburettor is taken from the front of the car (with the help of a big hose). So my advice is: get rid of the warm water arrangement!
By the way: why don't you buy the engine which Tony Fearn is offerig on this forum? the engine of the Rapier Series 3 A is a 1592 cc unit just like your Rapier series 4. It differs only on a few details like the oil filter. Regards, Peter