Original equipment intake and exhaust manifolds are bolted together to let exhaust heat keep the mixture in the intake uniform by assuring the gas doesn't condense and puddle in the bottom of the intake runners, especially toward both ends of the engine. Your aftermarket (racing) manifolds don't have that provision, so the mixture distribution between cylinders will be all over the map- - - -rich in the middle and lean on both ends. Racing equipment on a street engine is rarely, if ever a good idea. If those manifolds were actually touching each other things would be marginally better, but the gaps you've measured won't make things better, or worse. The aluminum intake on a street engine is also less than desirable. A 4 barrel on a 228 engine doesn't make good nonsense. I'd suggest that you find an original intake and exhaust and a 1 barrel Carter or Zenith carburetor, and do a P.T. Barnum move on someone who thinks he needs those manifolds. Good luck!
Jerry

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