new item made from alloy. Bare head with valve guides and valve seat inserts
Austin Healey BN4 to BJ8 (1956-68)
These replacement cylinder heads are made from cast LM25 aluminium alloy with a specially designed figure of eight valve seat integrally cast in. These inserts are made of a special stainless steel alloy to enable them to use unleaded fuel. This material has the same coefficient of expansion as LM25 aluminium and hence there is no possibility of the seat coming loose. As well as the obviously better heat dissipation of aluminium, it‘s use of allows a higher compression ratio to be used than would be possible with cast iron (approximately 0.5 of a ratio for the same type of fuel). There is also a weight saving, thus improving the weight distribution and therefore the handling characteristics of the car. Specifications: fully machined, balanced and polished combustion chambers with bronze valve guides and lead free valve seats.