All for .370 lift and under ........
@318willrun, is it true that a smaller intake valve ( 1.88" ) with good port work flows better than a 2.02" intake valve and no port work. Would the smaller intake valve be good for port velocity.
A lot to look at there. Flow will tend to be higher with the 2.02 intake valve and the generally associated larger port volume.
With judicious porting in the right spots to remove obstacles and enlarge where the flow naturally wants to go, the small port will tend to have higher port energy. This is basically flow speed and the mass moving to fill the cylinder more after the piston starts up the compression stroke and before the valve fully closes.
Now to your question concerning the valve, with a good 3 angle valve job and discretionary grinding to unshroud the valve, the 1.88" can work well. Besides the seat shaping, a 25° back cut on the intake vastly improves low lift flow as the intake valve just opens. The valve to seat form is the limitation on flow up to about 0.35" on most engines. With most of the older engines we are looking at probably having valve lift topping out at 0.53" even with an aftermarket cam, flow below 0.35" has a big effect on engine performance. What that back cut does is open up the valve to seat curtain area sooner. You want the flow to stay attached to the valve form so turbulence is not introduced.
So the answer is yes, a 1.88 valve and port can be modified to perform as well as or better than an untouched 2.02 valve and port.
To learn and get a better understanding, get David Vizard's Porting and Flow Testing book. Also good are his Powertec 10 Youtube videos. He discusses a lot of different topics that in his presentation may be directed at Ford or Chev, but a person can pick up tips or pointers that can be applied to other engines.
