Query on port-heads

[Zetomagneto]

The ports on the turbo Bantam were separated in a similar way

[Chris KC]

I'm not sure if I have the wrong end of the stick here, but I always understood Chapman (perhaps on another occasion) ran the camshaft backwards (i.e. by chain drive) thus converting the engine to 4 inlets / siamesed exhausts?

[Henry Harris]

Some more pics of the Lotus? manifold, sadly I don't have the block, or any parts of the engine. 

https://www.flickr.com/photos/henryharri...otostream/

https://www.flickr.com/photos/henryharri...otostream/

https://www.flickr.com/photos/henryharri...otostream/

https://www.flickr.com/photos/henryharri...otostream/

[Hugh Barnes]

I also understood the reversal of inlet/exhaust arrangement by Chapman as Chris KC recalls..

Doesn't make it true though!! :o)

[Robert Leigh]

...or was it all pert of ongoing development. I feel that the camshaft reversal and the divided ports may have come at different times. Colin Chapman was great at getting round the rules and changed his techniques as the rules changed.
Robert Leigh

[Chris KC]

More than likely I'd say Robert.
I'd be interested to know if that specific mod (the backwards camshaft) actually yielded a worthwhile increase in performance, if anyone happens to know.
And as Hugh points out, if indeed it is true!

[Hugh Barnes]

my understanding was that it was a succesful mod and that rules were immediately changed to outlaw it...

all from the dusty recesses though, so still not guaranteed!!

The Archive holds an extensive collection of 750MC magazines, so when the Archivist next gets to Lubenham, if he were given a rough date on when this might have happened, he could see if he could find any reports...

[geoffharrison]

Peter Ross  in his book  ' Lotus , The Early Years '  whilst describing in detail with photograph , the original block modifications to de-siamise the inlet ports and the subsequent special inlet manifold makes no mention of camshaft drive reversal . 
Whilst Chapman and friends modified a block to 8 port , he had already arranged for a similarly ported block to be sent from from Australia .

[Rogerfrench]

I have come to understand that the Mk III as raced by Lotus had a real, 8-port block with round inlet ports, and that Clive Chapman still has the block, which was planned to figure in the Mk V.
However, the Mk III as sold at the end of the 1951 season had indeed a couple of tongues projecting into enlarged inlet ports, as described above. That Australian Derek Jolly also de-siamesed a block seems beyond question, and that block made its way to Hornsey. Now, whether Chapman or Jolly did it first is debatable, we may never know.

There were several de-siamesed cars built after the 750mc relaxed the ban. My father owned one of them for a while, Complexity, whose engine lay almost on its side and had the manifold face of the block machined at an angle, removing metal from the lower edge so as to provide straighter inlet and exhaust ports.

[Hugh Barnes]

So, Roger, are we suggesting that 750MC newsletters from (say) 1950 and 1951 might reveal further details of the story? The Archivist can't recall what date the magazines go back to and it may be a while, of course, before he can find out...