Re: Snapey's 1935 Racing Biposto

Posted by Matt snape On 2011/2/23 7:10:05

That is correct Mal, the heads are a two piece design allowing for the water jackets and webbing above the combustion chambers to be machined into each each half. The spark plug screws into the lower half while the plug hole in the top half is oversized to allow for use of a socket to remove the plug. The temptation is to reduce the machining and cost by trying to use a thinner piece of alloy for the top section, but differental expansion can cause problems in getting the water jacket to stay sealed.

Out of curiosity Rusty, what do you think would be a resonable price for a flathead HC finned alloy head as you describe? Knowing this would give us something to aim at and would control our batch sizes and hence capital outlay.