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Lotus / Cosworth twin-cam spark plug placement


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#1 ed holly

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Posted 19 June 2012 - 23:35


Thought this might be of interest ...

The engine in my Brabham BT6 FJ-9-63 still has the original head on it as received from Cosworth in 1963 and fitted to the car by Frank Gardner at the MRD factory in 1963 in preparation for shipping to Australia for the 1964 Tasman Series, where Frank drove it as a A.N.F. 1.5 litre car. Incidentally this was the first Brabham to be factory fitted with such an engine.

I have always looked at where the plug holes are in the head, and intriqued to see that they are placed as close to the exhaust side as possible, this appears not to be the case with normal twincam engines. I have various other heads but they all appear to have the placement of plugs towards the centre.

The head cam-cover too is definitely original as photos show the breather it had at various Tasman events and I have the cut off part that was unique to it back then and the weld marks inside the head match the cuts where it was loped off. It always had and still has the Cosworth black plaque on top of the timing chain front of the cover.

Have a look at the photo and is this something unique to Cosworth prepared heads or is it something all the very early heads had.

Posted Image

Edited by ed holly, 19 June 2012 - 23:49.


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#2 Talon9999

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Posted 19 June 2012 - 23:52

Could it be to allow larger than normal inlet valves?

#3 Peter Morley

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Posted 20 June 2012 - 09:16

They did make some 8 plug heads.
One of them was for sale here:
http://www.race-cars...121284627ss.htm

#4 Bloggsworth

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Posted 20 June 2012 - 13:40

The standard cylinder heads had the holes in the middle, so I would think that the heads would have been supplied blank for Cosworth to finish.

#5 AAGR

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Posted 20 June 2012 - 14:10

The standard cylinder heads had the holes in the middle, so I would think that the heads would have been supplied blank for Cosworth to finish.


Keith Duckworth/Cosworth didn't believe in twin-plug heads. Somewhere in COSWORTH, THE SEARCH FOR POWER, he commented that if more than one plug was needed in a combustion chamber to get results, then the air flow was all wrong, which would have made him ashamed of himself ....