XPAG Crossflow Head

XPAG Crossflow Head

Michael Sherrell

April 2021

The other day some interesting information arrived from TC owner John Canty, in the UK.

He has an 8 port, alloy, crossflow, XPAG head made by Robert Cowell (later Roberta Cowell!), the

origins of which are unknown to me, but in 1954 Mike Costin acquired one while working with Colin

Chapman on the Lotus 8, Frank Costin’s first streamliner SAR 5. The original heads had a small

‘Cowell’ cast in the side, but the Chapman ones did not!

John came across the head at a motor spares place when he went looking for a pair of SU air rams. We

could be so lucky! His head does not have the ‘Cowell’ cast in, so it might be a Chapman one. John

was a TC racer (TC/1403) back in the days when TCs filled the grids in UK. He could have done with

the head then!

The story gets more intriguing: with the letters and photos John sent me, came a photocopy of a letter

addressed to him from Keith Duckworth himself (of Cosworth Engineering) dated 10/05/91. In it he

outlines some of the history of these heads, and it goes like this:

“ It was Mike Costin who was with Colin Chapman at the time – 1954 – He had just returned from

holiday. They used a crossflow aluminium head, which was made by Robert Cowell – who incidentally

became Roberta Cowell by the assistance of the odd operation or two. Some heads had a small

COWELL cast on the side of the head. The Lotus had not got the Cowell name (and we all know why!)

Had a leak from pushrod hole to exhaust port, which Mike Costin lined with a copper tube. Mike and I

think the heads were very rare… Best wishes Keith Duckworth”

Looking at the photos one can see the spark plugs have been shifted to the off side to be with the four

individual inlets and enter the (minimal) combustion chambers over the inlet valves. There appears to

be little or no water flow block to head and minimal oil drain head to block. One can only guess at the

compression ratio (high) and it would be pretty difficult to blow a head gasket with all that flat area.

Exhaust ports are round as are the inlets.

The whole design looks very appealing, pity they are so rare.

I believe these heads may be the source of some confusion over the Laystall Lucas alloy heads,

sometimes thought of as crossflow heads, which they were not. I would like to thank John Canty for

going to trouble and expense to share this interesting bit of XPAG history with us.

Almost as interesting as the heads themselves is the story of Robert Cowell, who later became Roberta

Cowell after a series of operations, becoming a forerunner in the story of gender change. It’s worth

looking up Robert/Roberta Cowell on line: Spitfire pilot, racing driver, talented engineer and

pioneering transgender person, just a bit ahead of ‘her’ time.