Cylinder head
Austin Healey: BN1 and BN2 (1953-56)
new item made from alloy. Fast Road specification, complete with valves, guides and springs
We have developed a replacement cylinder head for the 6-cylinder cars similar to the type used normally by the works rally cars. This is cast in 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 originally developed for Ferrari 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. We have fortunate in our initial development stages to be able to section on original aluminium head and therefore to be able to increase material thicknesses in areas where the original aluminium heads were weak. This information, together with original drawings, enabled us to redesign the head to ensure a durable and robust product. 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 of approximately 20 kilograms, thus improving the weight distribution and therefore the handling characteristics of the car. If combined with a high ratio steering box the car is transformed. We have carried out many of thousands of miles on long term testing using one of our own cars. The car (late BJ8) was fitted with one of our standard lead free cylinder heads using a compression ratio of 8.5:1 (the standard car is about 9.3:1) and has used only regular lead free fuel. The car has run faultlessly and performance in fact is better than with the original cylinder head (probably because of the polished and balanced ports and combustion chambers). Most of the successful competition 6 cylinder Austin Healeys are now using our cylinder heads and have covered many thousands of racing and rallying miles all around the world. Specifications: 8.5:1 compression ratio, fully machined, balanced and polished combustion chambers. Polished ports.v
Accessory Cylinder head
