[Ed Wright]

Years ago we used to fill the 300-25 with epoxy to lessen the cross section. They were quite large. I had one on my old 292" C/SM Camaro. Garley Daniels put me onto Dave Jarvis (Air Speed Engineering) to have one done. Even that 9000 RPM stick car liked the runners filled. Leaves you a lot of leeway for tailoring it to your engine, if you can shut the hood. Pretty tall after you add your spacers. Best flowing manifold I ever tested, filled or not. With simple port matching, it was the only manifold I've ever seen that made my Lee Shephard C/SM heads flow 1 to 2 CFM more than the radiused entry plate, at least on my self-built flow bench.
I bought a couple of Edelbrock and one Offy due to people's claims of them making more power. I had never had access to a dyno back then, (weren't many around in the 1970s) but none ever went down the race track as fast as the 300-25 manifolds did on my car. I would guess they might need a lot of epoxy on an automatic car.