Hello everyone. I'm a new ACOC member having recently gotten a 1979 21' with 440 ci engine. Have been busy working away at the interior and the unit is now awaiting a new engine. I've been reading most of the old posts on the benefits of opening up the exhaust to improve performance and mileage. Seems that people have either gone with headers or with dual exhaust and in both cases reported favorable results. I realize that headers may reduce doghouse temps, although I have seen the opposite also suggested. Overall, does anyone know if one approach would give more benefit and the pros and cons of each. Also, what kind of mileage improvements have you seen in either case? I appreciate all of the good member input. Thank you, Al Nelson
AL
I would consider both with a crossover tube just behind the header collectors. You should also consider the headers with the ceramic coating on both the inside and the outside. They do a much better job of keeping temps down (cost more also or send them to someplace that will coat them after you purchase). The crossover tube will balance the pressures between each side and help cut the exhaust noise.
We had some 'long' Thorley headers installed with new stock mufflers, both exiting out the left side in front of the rear tires. The headers are not ceramic coated but the heat generated is still much less than the stock manifolds. I don't know exactly what improvements this accomplished because I installed a new Edlebrock aluminum manifold and carbeurator at the same time.