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Jul 21st, 2025 | | | | Joined: Sep 2008 Posts: 289 'Bolter | | 'Bolter Joined: Sep 2008 Posts: 289 | The engine is a 250ci inline 6, all stock except for a stock GM TBI, Clifford intake and Langdon's Stovebolt 2-piece cast iron headers. The engine is followed by a th700r4 trans. What matters most to me is low/mid range torque and power. I also want a single line exhaust.
What is the best exhaust pipe diameter for this?
Also, any good idea for a muffler (rather quiet, no drumming noise)?
Thanks!
'57 Chevy Suburban; '70 Chevy Impala.
| | | | | Joined: Dec 2008 Posts: 1,915 'Bolter | | 'Bolter Joined: Dec 2008 Posts: 1,915 | The exhaust restriction is fixed by the outlet size from the manifold to the head pipe. You can make it 6" and it won't matter.
For a mild engine, a single 3" (= to dual 2-1/8") is enough for 200 real HP (rough calculation of area: square root of HP รท 24 gives the ID, add .098" for 18 gauge, .118" for 16 gauge to get the OD).
Easiest rule for a muffler to get reasonable noise and best power: the largest one you can fit. The internal volume plays a major part in killing noise and harmonics. | | | | | Joined: Apr 2010 Posts: 474 Shop Shark | | Shop Shark Joined: Apr 2010 Posts: 474 | I ordered a kit that fit great from this site and you can pick the type of muffler you want .http://waldronexhaust.com/shop/index.php | | | | | Joined: Feb 2000 Posts: 4,886 'Bolter | | 'Bolter Joined: Feb 2000 Posts: 4,886 | Since you haven't really increased the air flow into or out of the engine, 2" to 2 1/4" would be fine. 2 1/2" would be as big as I would go. The stock head and cam regulate the air flow, stock engines came with 1 7/8" or 2" pipe.
Dad's race car has a 478 cu in engine and it runs best with 3" pipe to the mufflers and 2 1/2" tail pipes. 4200 lbs and runs 11.30's at 117 mph in the 1/4!
Find you a dual inlet single outlet muffler, then you have the best of both. Duel pipes up where you need them, and single tail pie for easy and longevity. To little air flow can't keep the pipes hot enough to burn out the water and acids which eat away at the metal.
Joe | | |
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