Lelo,,,,,,,
Looking at your '318' Engine Modifications.
* KB 167 +.030" Pistons Flat-Top Pistons with Notches = (9.0 - 1 Compression)
(9.5 - 1 Compression with a Decked Block)
* Comp-Cams EX268-H
.454" Lift / 268* Duration / 110* LSA / 106* CL (218* @ .050" Lift)
* Comp-Cams Valve Springs #901 (#242 Load-Rate @ 1.250")
* Holley 570 CFM (Avenger)
* Edelbrock Performer Intake
Everything states a Maximinum RPM of 5500 for 'peak horsepower'.
Stay with the 1.78" and 1.50" Valves, and perform your own minor 'Head Porting'.
A) Gasket Port Matching for both Intake and Exhaust
B) Round off the Valve Guide Boss in the 'Valve Bowl Areas'.
C) Remove any 'high spots' or 'cast flashings' inside the Cylinder Head Ports.
I'm sure you are having the Machine Shop perform a Competition Multi-Seat Valve Job,
with a minimum of 5-Angles (70* - 60* - 45* - 30* - 15*) in the Valve Seat.
And a 30* Back-Cut (.025" Wide) on the Intake Valve, as this will improve CFM greatly
through the Intake Port.
The #4323302 "High Swirl' Cylinder Heads can be a 'Funtional Mid-Performance Head', and with
some 'smart tricks' are a decent component on a 'Mild-to-Moderate' Street/Strip Performance 318.
The 'key' to this Cylinder Head, is getting a proper Competition Valve Job, and blending the 'small'
Intake Port to 'match-up' with the Performer Intake Manifold.
The 'Best Trick',,,,,,,,, matching the Cylinder Head Intake Ports to the Performer Intake Manifold.