The Hardcastle books have info on valve sizes. The pre-sd1 had 38mm inlets
and 33.3mm exhausts. The SD1 had 40mm inlets and 34mm exhausts. You can fit
41.4mm and 35.5mm valves on the standard SD1 seats. These are commonly
called big valve. With bigger seats you can use 43mm/37mm and this is the
size used on many TVRs.
The SD1 inlet ports measure 25mm x 39mm at the outer end. The RV8 heads
are 25mm x 40mm. My standard SD1 heads are ported to 26mm x 43mm.
SD1 exhausts are 20.5mm x 31.5mm. RV8 uses 24mm x 34mm. My ported SD1 heads
are 28mm x 38mm.
Regards,
Ian
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Ian Crocker ian@btcase.bt.co.uk www.seight.com
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