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Author
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Topic: Opinions needed on exhaust for 351C (Long Post)
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mach72
Gearhead Posts: 135
From: Bixby, Ok. USA
Registered: Jun 99
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posted 02-27-2005 09:57 PM
  
Hey guys, My 72 mach 1 currently has 1 3/4" Dynomax headers, stock 2 1/4" dual exhausts, and some turbo mufflers of questionable age/manufacterer. I am replacing the headers with some Hooker super comps (2" primary, 3 1/2" collector) ceramic coated. I would like to replace the exhaust with: 3 1/2"inlet/3" outlet header reducers into flowmaster smooth transition header reducer cones with 2 1/2" outlet, into 2 1/2" summit x-pipe, into Hooker max-flow mufflers into 2 1/2" flowmaster mandrel bent tailpipes. My goal is a near zero loss exhaust system that maintains some flow velocity for good scavenging. But one that is not louder than it really has to be. What do you guys think about my plan. This is a street/strip car (not a daily driver). The rest of my combo is: Holley 700 DP, Blue Thunder Dual Plane Intake, 4V O.C. heads (9.5:1 comp) (Manley stainless valves, polished chambers, cleaned up exhaust ports, machined for screw in studs/guideplates), Harland Sharp Roller Rockers. Block: 4 bolt main, bored .030", KB hyper pistons, resized rods with arp bolts, stock crank .010"/.010", balanced recip. assembly. Cam: Cam Research Hyd. 290/300 dur. (226/235 @ .050"), .550"/.570" lift as measured (cam card reads .540/.560) 111 lobe sep., 5 degrees advance built in . Trans: C6 Roller Bearing, wide ratio (2.72, 1.54, 1.0) gearing. Rear diff: 9" 3.50 trac-loc 31 spline axles (the wide ratio C6 will make the 3.50 gear pull like 3.91's in 1st gear, 3.70's in 2nd gear. Converter is a stock CJ converter rebuilt to a true 3000 stall. Car weighs approx 3550# with driver (measured 3420# without full interior. Thanks guys sorry for the length, Tom
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Scott (69Mach)
Gearhead Posts: 787
From: Walnut Creek, CA USA
Registered: Jun 99
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posted 02-28-2005 10:43 AM
2" primaries seems pretty big for your application. I'd think the 1 3/4 you have now or a set of 1 7/8 primaries would be a better match. The rest seems in line.Good luck, Scott
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n2oMike
Gearhead Posts: 2680
From: Spencer, WV
Registered: Jan 2001
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posted 02-28-2005 11:22 AM
Run your existing headers into a 3" X-pipe, back to 3" mufflers, then weld 3-bolt collector rings to the muffler outlets so you can hook up REMOVABLE tailpipes with ordinary header reducers. The removable tailpipes will allow you to tailor the exhaust to suit your mood. They will also make it easy to remove the entire exhaust system for transmission maintenance, etc. (try doing trans maintenance with an X-pipe and no removable tailpipes) ------------------
Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367
http://www.mustangworks.com/cgi-bin/moi-display.cgi?220
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Hemikiller
Gearhead Posts: 661
From: Killingworth, CT
Registered: Feb 2002
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posted 02-28-2005 04:57 PM
I'm with Mike, too big of a primary tube for the size cam and rear gear you have. Do a 3" pipe collector to muffler. I'd recommend AeroChambers over the MaxFlo if you want it reasonable quiet. To make use of those 2" tubes, you'd need to step that cam up to the 245 @.050" range or more and use some 4.30's or 4.56's. If you want new headers, you could get the Hooker Comps, which are 1 3/4" tube also, but fit much better than the Dynomax's.
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mach72
Gearhead Posts: 135
From: Bixby, Ok. USA
Registered: Jun 99
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posted 03-02-2005 01:50 AM
Thanks for the replies. I bought the super comps new for about the same price as comps (bought them from an engine masters competitor). My Dynomax headers only have about 21" primary tubes which makes them tuned for about 9-10K rpm. The Hooker super comp primaries are approx. 36-38" long which makes them tuned for about 4800 rpm. I was hoping that the ceramic coating would keep the velocity up some since it retains more heat in the primary pipes. Then by using the 2 1/2" exhaust it would keep the velocity up. I do plan to switch to a solid cam of about 240 dur. at .050, approx 275-280 seat duration and .580-.600 lift and a 108 lsa. But I'd like to get a baseline with the current cam first. Thanks guys, Tom
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n2oMike
Gearhead Posts: 2680
From: Spencer, WV
Registered: Jan 2001
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posted 03-02-2005 11:43 AM
You're going to need the 3" exhaust with those huge headers. You need velocity through the headers.... not the exhaust system. Choking the system after the headers does nothing for velocity.------------------
Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367
http://www.mustangworks.com/cgi-bin/moi-display.cgi?220
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