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How big a exhaust pipe do you really need for a 4bt? I am accumulating parts for a conversion now. I want to put a 3200rpm spring in my pump. my chevy 400 had 400+hp and had dual 2.5" exhaust good enough to 6200rpm. 2X2.5" pipes have the same area as 1X3.125 pipe. 400CI=6.5L. 6.5LX6200=40655LPM=/needs 3.125 pipe.
4bt numbers: 3.9LX3200=12480lpm/40655lpm=3.2 or about 1/3 the LPM flow requirement for exhaust............................................So lets now double this because of the "unknown factor" and say the 3.9 needs 2/3 the flow of my 400. This equals approximately 1X2.5" pipe.
I now have some 2.5" pipe from my old exhaust and 2X flowmaster 50 series with 2.5" in/outs. The flowmaster 50's are too loud by themselves. If I have a 2.5" pipe leading to 2Xflowmaster 50's in series I think it will be quiet enough and not too restrictive.
Anyone else got a different opinion or think 2.5" is not big enough for a 4Bt?
4bt numbers: 3.9LX3200=12480lpm/40655lpm=3.2 or about 1/3 the LPM flow requirement for exhaust............................................So lets now double this because of the "unknown factor" and say the 3.9 needs 2/3 the flow of my 400. This equals approximately 1X2.5" pipe.
I now have some 2.5" pipe from my old exhaust and 2X flowmaster 50 series with 2.5" in/outs. The flowmaster 50's are too loud by themselves. If I have a 2.5" pipe leading to 2Xflowmaster 50's in series I think it will be quiet enough and not too restrictive.
Anyone else got a different opinion or think 2.5" is not big enough for a 4Bt?