Not sure this is relative for your 23* engine but my Dart 18* heads have a Dart single 4 intake with a 4150 flange. I had considered cutting that flange off and making a 4500 flange but Curtis Boggs told me that the funnel adapter would do better than my idea of changing the flange.
Having said that, last year I cut the crap out of the inside of that funnel adapter in the area where it meets the manifold flange. When I got done there was only about a quarter inch of the original 4150 flange left and that intake ran damn near as good on a single Dominator as it did with a sheetmetal intake with dual 750s. Now I did open up the ports all the way to the head flange too so not all the performance gain was from opening up the plenum area of that 4150 flange.
I got this idea from another member who had posted some pictures of some plenum porting he had done on a 23* intake that netted him some significant performance gains. Here's a link to that thread.
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Big Boyz Toyz!
Necessity is the plea for every infringement of human freedom. It is the argument of tyrants; it is the creed of slaves.
William Pitt, British Prime-Minister (1759-1806)
