What have you done today with your Austin Seven

[Malcolm Parker]

Regarding the wedged low compression head, the machining alters the shape of the combustion chamber significantly.   The final shape depends on the angle that the machining is done at, also the amount that is taken off.   The three wedged heads that I have had were machined on a lathe, and all are different.   The head that was on the Pytchley was machined with 4mm difference one side to the other, I think this is about as big a wedge as you can probably go.   The thickness of the castings vary so there is always the chance that if you go too far, you may break through the head of the combustion chamber into the water jacket.   Our technique was to make several cuts and keep an eye on the shape of the combustion chamber, stopping when it looked okay.  All very unscientific.  It is amazing how the shape of the chamber develops after a certain point.   The Pytchley head ended up with a combustion chamber volume of 23.2 cc, according to my calculations, which gives a CR of about 7:1 with the gasket.  The more the angle of the wedge, the more you need to open out the stud holes in the head.
This head is going on a new engine I am finishing off for the Ulster, it will be interesting to see how it compares with the Ricardo head fitted on the present engine.