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I will try to attach the displacement curve on which I based the cam design. I havn’t changed it so I expect it is the same as the one you have recorded Colin. Sorry file is too big for this forum. If any one would like a copy please let me have your e-mail or postal address.
I get about 24 mpg and can be over 30 on a good long run. BUT I am running on 9.5 : 1 CR and find I need the best fuel – Shell V power to avoid pinking.
I have now rebuild my engine and installed new camshafts from the Club (with more rounded cams as opposed to my previous camshafts which had very flat lobes – see the picture I uploaded earlier in this discussion). Everything is now perfectly set with the recommended 24 degrees valve overlap and the problem of petrol spit-back through the carbs has completely disappeared. It was indeed simply a matter of the wrong combination of cam profile/downdraft cylinder head/valve overlap.
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