The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - What exhaust to use? Suggestions and pics

llowlife · 10-07-2010, 11:29 PM

If you truely will be building 550 hp you will need 2.2-2.5 cfm exhaust flow per hp or roughly 1100 cfm. You will need to ditch the FM and buy some Magnaflows or Dynomax mufflers. 1" square will flow roughly 115 depends on bends etc. 2.5 inch pipe will flow a whisker over 500 x 2 for dual exhaust. 3" is sneaking up on too big but is still fine for 550 hp as it has about 7 sq inch or roughly 800 cfm x2=1600 cfm. I would go 3" if it were me in this situation. Flowmaster mufflers kill HP....Period....Dynos don't lie. The dynomax turbos will kill HP too as if I remember correctly they are a 3 pass system. Buy a straight through muffler. All glasspacks are straight through but are not necessarily built the same. All numbers are a bit "loose" as I couldn't find the calculator so I had to do them by hand.

Oh yeah run an "H" or "X" pipe as it will quiet it down and possibly add some HP over an otherwise "H less" system.

10-07-2010, 11:29 PM	#15
llowlife Registered User Join Date: Jan 2010 Location: Elgin Mn Posts: 112	Re: What exhaust to use? Suggestions and pics If you truely will be building 550 hp you will need 2.2-2.5 cfm exhaust flow per hp or roughly 1100 cfm. You will need to ditch the FM and buy some Magnaflows or Dynomax mufflers. 1" square will flow roughly 115 depends on bends etc. 2.5 inch pipe will flow a whisker over 500 x 2 for dual exhaust. 3" is sneaking up on too big but is still fine for 550 hp as it has about 7 sq inch or roughly 800 cfm x2=1600 cfm. I would go 3" if it were me in this situation. Flowmaster mufflers kill HP....Period....Dynos don't lie. The dynomax turbos will kill HP too as if I remember correctly they are a 3 pass system. Buy a straight through muffler. All glasspacks are straight through but are not necessarily built the same. All numbers are a bit "loose" as I couldn't find the calculator so I had to do them by hand. Oh yeah run an "H" or "X" pipe as it will quiet it down and possibly add some HP over an otherwise "H less" system. __________________ In the beginning of a change, the patriot is a scarce man, brave hated and scorned. When his cause succeeds however, the timid join him , for then it costs nothing to be a patriot. I am a revolutionary...so my son can be a farmer...so his son can be a poet. If there must be trouble, let it be in my day, so my child may have peace... 72 short step w/ 388 /4l80e/ and 3.08 gears. Last edited by llowlife; 10-07-2010 at 11:48 PM.