Bronze cylinder heads.

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patrick.robotham
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Bronze cylinder heads.

Postby patrick.robotham » Sat Oct 19, 2013 4:56 pm

A friend of mine is thinking of buying a 1932 four valve 500 VH or VG. The odd thing about it is it has a bronze head. I have never seen another four valve bronze head. I know these models had a habit of the cast iron heads cracking and i know there are two valve bronze heads out there some supposed to be of factory origin and some aftermarket, etc . So anyone know anything about this particular, type four valve bronze head. Pat

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adrie.degraaff
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Re: Bronze cylinder heads.

Postby adrie.degraaff » Sat Oct 19, 2013 5:31 pm

Yes a friend was offered a bronze aftermarket 4 valve head.

nevhunter
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Postby nevhunter » Sun Oct 20, 2013 12:43 am

Rudge used them (I had a 35 Ulster) The head weighed 38 lbs. Gipsy Major 1-c engines use them. You can run the valves onto the bronze seats as long as you don't use leaded fuel. I have had an aftermarket one for speedway JAP too. Nev

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Postby jim.haydock » Tue Oct 22, 2013 7:52 am

Bronze heads were a precurser to aluminuim heads in the days before high strength alloys were more generally available, the advantage being that they conducted heat away from the combustion chamber at a much higher rate than cast iron. This had the advantage of reducing the combustion temperature and hence the risk of detonation with higher compression pistons and giving the exhaust valves - always a source of troubles in earlier days - an easier time. Aluminium alloys were an even better heat conductor and became more commonplace towards the end of 1930's and beyond in high performance engines. For further and better particulars check out Kevin Cameron's excellent book - Classic Motorcycle Racing Engines - definitely one for the Christmas List!

Jim Haydock

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Postby nevhunter » Tue Oct 22, 2013 8:22 am

Jim, The weight of the things takes a bit of appreciating. Also attempts at inserting them were not always successful. Lead destroys the bronze seat in a short time if it is in the fuel. Cracking between the exhaust seats was common which is a place where excess heat occurs Rudge ended up with an alloy head around 1938..Nev


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