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#50472 09/23/2005 11:18 AM | Joined: Jul 2005 Posts: 71 Member | | Member Joined: Jul 2005 Posts: 71 | I need to replace the whole system on my 42 ccw (270). Originally 2.5" from manifold to muffler, then 2" outlet & tailpipe. Why the step-down in diameter?Is some back-pressure any advantage on this motor, or is 2.5" right through better? Opinions seem to vary. :confused: Thanks | | |
#50473 09/23/2005 2:20 PM | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 | The less back pressure the better. Use 21/2 all the way back. The only advantage would be a little quieter.
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne SuperIn the Gallery Forum | | |
#50474 09/23/2005 4:29 PM | Joined: Oct 2003 Posts: 5,152 Cruising in the Passing Lane | | Cruising in the Passing Lane Joined: Oct 2003 Posts: 5,152 | I've got big pipe all the way back on my 270 and it seems to like it. It may not be as quiet as 2-inch but its not noisy either.
The only other exhaust system I've run on my 270 had some crude openings all along the length. It was noisy.
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#50475 09/23/2005 5:11 PM | Joined: Mar 2005 Posts: 1,029 Member | | Member Joined: Mar 2005 Posts: 1,029 | The step down in diameter was probably originally done to decrease the size, weight and especially the cost. It doesn't create any more backpressure because the volume of exhaust is less by the time it gets through the muffler due to cooling. Most vehicles had smaller exhaust pipes than head pipes. | | |
#50476 09/24/2005 4:25 AM | Joined: Nov 2003 Posts: 53 Member | | Member Joined: Nov 2003 Posts: 53 | Also keep in mind that a smaller exhaust pipe keeps the exhaust velocity higher, which helps prevent cooling and condensing of vapors in the pipe. The small pipe will last longer, as well as be quieter. If you're running a stock 270, 2" will work fine. | | |
#50477 09/24/2005 5:48 AM | Joined: Jun 2000 Posts: 2,773 'Bolter | | 'Bolter Joined: Jun 2000 Posts: 2,773 | And it also helps low end torque by keeping the exhaust speed up.
Fred
52 3600
69 C-10
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