my slant buildup

The valves can certainly affect the volume. I used BBM1.74" exhaust valves for intakes, but they were more tulip-shaped, & the chamber face of the valve-head was very recessed. I cc'd it, & it checked at 2.4cc, the Max-Wedge 1.88" face checked at 1cc,..& was larger.
With the 1.74/1.41 setup My drool-tube head checked at 58.6cc, & ended up at 50.5cc after takin'.055" off. Oh, & after close to 30K on the unit, it lost a bit over .5cc due to carbon buildup that wouldn't brush/wipe away. Hope that is helpful.