exhaust manifold

The hot spot in the manifold is to prevent drops of fuel (the fuel leaves the carburetter as a spray, not a gas) from pooling where they hit the bottom of the manifold and causing mixture to vary between the inner and outer cylinders.

The thermostatic variation of this hot spot was dropped in later production, so it presumably was found to be not necessary. The bimetal strip adjusts the position of a flap allowing the exhaust to hit the hot spot directly when cold but deflects it when warmed up so that the hot spot warms up more quickly - probably not a significant improvement except in very cold climates.

John

Thanks chaps.

So nice to know that the bit that broke off wasn't really necessary anyway! :)

And thanks for the explanation of the hot spot. As someone who has never really had an opportunity to 'get down and dirty' with a project like this, I am fascinated by all these little gems of information along the way.

cheers,

Garry

If you are not going to repair flap so that it operates properly it is important to make sure it is fixed in the open position,ie exhaust deflected away from the hot spot as it will slow exhaust gases leaving the ehaust chamber area and can cause burning of exhaust valves. Regards John