Choosing Between MagnaFlow Exhausts MF15893 and MF15897 for 1967 Oldsmobile 442

Question:

Looking to change out an old Flowmaster exhaust and replace with Dougs headers and your magnaflow stainless steel system. Im just not sure if I should install the larger diameter exhaust or smaller. The article regarding pipe diameter states that bigger is not always better. My 1967 442 is a 4 speed stock 400cid. Is there a significant increase in horsepower comparing the 2.5 to 3 inch diameter tubes? I do see a significant price increase. Is there really a difference with crossback exhaust? Will this crossover exhaust fit under my car without any modifications?

asked by: Terrance

Expert Reply:

The two MagnaFlow crossmember-back exhaust systems you referenced, parts # MF15893 and # MF15897, differ primarily in their cost and pipe diameter, as you noted. Both systems are 100-percent stainless-steel exhaust kits that include all hardware, straight-through mufflers and a true X crossover to balance airflow for improved power.

I would stick with the 2-1/2-inch diameter kit # MF15893 unless you have the 4 barrel carb and are using a high-performance air filter. Air intake and exhaust output are two ends of the same breathing system so unless you have increased intake there is little benefit from using the 3-inch diameter exhaust. For reference I have linked the available air filters we offer for your 442.

Both kits are designed to work with OEM-style exhaust manifolds or tubular headers, but since applications can vary some modifications and/or welding may be required for proper installation.
Instructions for both kits are linked for you along with an installation article.

expert reply by: Adam R