Notes
Notes
This page was last updated on $Date: 1999/03/04 12:03:43 $.
Originally posted on the SOL healey mailing list: Sat, 27 Feb 1999
Many books that mention the 100S refer to the car having possessed a cross flow head. I fear the change of sides to allow freer porting arrangements confused many, including Jeff Clew, when he wrote 'Lucky All My Life', the biography of Harry Weslake, where on p68 he states 'Harry obliged again by developing the engine into what was to later known as the 100S. This featured a crossflow cylinder head and required modification to the top deck of the cylinder block (sic!) to accommodate.....'
Yet, there is some room for error with this one......... Westlakes' were experimenting on DHMCo's behalf with a type of 100S head that was not in fact crossflow, but more correctly dualflow. To be specific, as well as having the intake and exhaust manifolding in its usual place, the off side carried two smaller inlets, where two additional carburettors were positioned, ie running with four carburettors. Weslakes' idea, stemmed from similar work that thay had done on MG's, with a view to having a greater volume of gas in the larger chamber behind the valves.
Yes, it did produce more power, unfortunately only if you manipulated the throttles independently throughout the range. A minor problem, not able to be solved prior to a time when they lacked Pentium 3 computers and regularly putting men on Mars! In the end, Weslakes came up with the idea to put an equalising pipe across the two inlets on the offside and with that gave up on the rather expensive project.
To my knowledge a couple of dualflow heads existed, I managed to buy just one of these heads, including the test data, from Weslakes, as it was still laying under the bench twenty years after testing ceased. Incidentally, you can pick Westlakes test heads, they will be stamped on the rear vertical face of the head, in the case of my head, RA249, or whaterver the test number will be. The R stands for Rye (the town on the English South coast, East of Brighton where Westlakes are located), and the A stands for, yep, you guessed it Austin! (Oh, I might mention before anyone rushes to the phone, I picked that place cleaner than the turkeys breastbone on Thanksgiving day!)
Despite the known problems, a friend subsequently fitted it to AHS 3909 in four carburretor form. Impressive under the bonnet it was, the eventual resulting reasonably specactular fire, was not! With the 100S surviving, the dualflow head was again reduced to the role of a interesting doorstop.
Please send comments, additions, and errors for the SOL Healey web pages to Bob Haskell.
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