Valve to throat ratio. Is a bigger valve always better?

[Bobby Shaftoe]

The initial message was deleted from this topic on 17 August 2017 at 01:35

[Bobby Shaftoe]

I do actually have a set of 43/37mm valves spare, only problem being they're on a 5/16 stem (with a triple groove retainer) rather than 11/32.

I tried to source the guides, Paul at REC suggested they were Ford X-flow/Essex/Pinto but a call to burton power later it appears the OD of the ford guide is way too small. Not sure if the pinto triple groove collet fits the rover valve spring retainer either.

I think the cost of seats/guides/collets etc and the associated machining work would put the 43mm's way over my budget.

[Bobby Shaftoe]

Well finally got round to getting the heads off and recutting the seats. A quick and dirty test on my flowbench showed 167cfm with the recut seats and 1.63" versus 158cfm with standard valves. (My bench isn't calibrated to anything in particular but a stock unported rover head flows around 136 cfm peak, all at 28" h2o)