S - Exhaust System
When I bought the car it had a stainless exhaust made by Falcon. I have been told that these were cheap and nasty because they were very inaccurately made, which is true. The rear pipes that wiggle over the axle were simply not symmetrical so the silencers just could not be aligned and always looked wonky. This was fixed by judicious heating and bending, which was fine until I did the Getrag conversion.
Exhaust Manifold: It is a common problem for the cast iron exhaust manifold to crack, and it is said this can be prevented by drilling out the holes for the mounting studs by one drill size, thus allowing more room for expansion. I have done this, but there again I have never had a problem and the manifold could well be original. I suspect there were good castings and bad ones, although in recent years it has been possible to buy replacement manifolds with a slightly more robust design that should not to crack. They are relatively expensive, in the region of £250. The 907 and 912 engines use the same manifold.
Downpipe: This item is different between S1 and S2, so if you are doing a Getrag conversion you will need the S2 item. This has a flexible joint in it, and is designed to clear the Getrag lower mounting bracket.
Centre Box: Again the S2 car uses a slightly different box which is designed to be supported from two large rubber rings that hang onto a front and rear mounting point. The S2 chassis (or the modern universal S1/S2 galvanised chassis) has these mountings fitted, but in my case I had to make them myself since I was still using a S1 chassis. I am really proud of this bit. Some of you will say its a terrible bodge, but its not. I found a part that is very substantial, galvanised and fits perfectly. It is supplied with two fixing holes and when in place aligns perfectly with the correct mounting rubbers. It is the latch from a common garden gate, found in all good hardware shops, and costs about 50p! If this offends you, then I suggest you read "Zen and the Art of Motorcycle Maintenance" to understand why you are wrong.
Another mod was to reduce the amount of heat soaking into the cabin. Above the centre box is an elongated hole to allow access to the rear end of the gearbox for installing the prop. I made a steel plate and screwed it over the hole to prevent heat rising from the silencer into the chassis and therefore into cabin. This plate (painted red to match the Spyder painted chassis) and the whole length of the underside of the chassis is covered with an aluminised, heat reflecting material, again to reduce heat soak.
This centre box was purchased from Double S Stainless Exhausts and fitted properly, but unfortunately I wanted to mate it to the original Falcon wiggly pipes, and the diameter of the two output tubes is larger than the wiggly pipes. I tried various shimming bodges, but gave in and had the wiggly pipes modified to fit the centre box correctly. Looks professional (it was, this was done by Cheesemans, a manufacturer of stainless systems in Woking who coincidentally used make the exhausts for Lotus F1 cars many years ago!).
One problem was that the exhaust always seemed noisier than I expected and eventually I realised that the centre box was completely empty - no stuffing at all! Double S said that this was the standard spec, so I asked them to supply me with another box which was properly stuffed. They did this at a reduced cost since I was an existing customer, and it is quieter, but not by a huge amount.