thats my opinion on it, cause when you do...it go's from narrow to wide and then narrow again cause of the push rod pinch that you cant avoid in factory castings without tubing. so opening that side to the gasket is like pointless to me. The j heads in the pick above do not have the window opened on the push rod side, just thinned the pinch...and they flow 280's, so much for needing the window matched all round.lol:happy1: