The LA 318 and especially the 1970's version had a carrot up its arse in the form of the camshaft. With the OEM cam any improvement possible with the upgrade to a 4V carb and manifold will be minimal. Changing to a 360 or 340 cam will greatly aid what the 4V will add. Keep the intake duration at 0.050" lift down to a max of 220°. Valve lift approaching 0.500" is desireable.
The valve curtain area is what controls the intake flow up to about 0.25D of the intake valve. Thus with a 1.72" intake valve, the valve has to open to more than 0.43" for the port to be the limiting factor. With a 1.88" valve that lift becomes 0.47". Shooting for 0.500" lift just gets you into port limited flow for a few degrees more, allowing faster intake velocity and better cylinder filling just prior to IVC. What does that mean? Better torque and drivability.
To get that lift on the intake may require changing the intake rocker ratio up by .1. Ben Alameda has a video where he discusses more power with smaller exhaust valves. The basic premiss there was a smaller exhaust allows larger intake valves. A NA engine has at best 14.7 PSI pushing air into the cylinder. At EVO the cylinder pressure is generally about 70 to 120 PSI. On blown nitro engines making 1,000HP or more per cylinder, that may be higher which requires much stronger lifters, pushrods and rocker arms due to the force against the exhaust valve head resisting it opening. Now those engines may be using 1.8" to 1.9" exhaust valves, which sounds big. But the volume of air and fuel crammed in and then combusted causes a huge volume increase by the heating.
The exhaust on our performance street or street and strip engines can function very well on small (by comparison) exhaust valves and/or a bit lower lift.
Newbomb the Turk and possibly a couple of others are liable to be triggered by this. To him/them I say, before your wood runs away with you, go watch and listen to what Ben has to say. It is a bit frustrating as I believe an outside door may have been open allowing traffic and helicopter noise in.
