318 Port match heads to Performer RPM Intake
The air gap manifold seems to be a mismatch to the rest of the combination. That’s a higher rpm manifold on an engine that Likes low end torque.
the air gap seems to be more of a manifold for high compression, higher duration cams, 360 heads, and makes power more at the top end. You can’t really have this well without over 9:1 compression at least
A performer manifold if fine but I would like to see the ld4b or it’s copy cat weind action plus. The performer seems to be like a stock 4 barrel
In my research of building the 318 and my current build I find that
Whiplash or xe262 or similar with low compression
4 barrel
Dual 2.5 exhaust
Ported heads matched to intake
Action plus or ld4b
that’s close to the best combination a low compression motor can get
also the thin head gaskets and .030-.040 taken off the head.
I’ve wondered lately if the stock 68 318 heads are as good as the 302 Heart shoes heads for low compression engines