Reply To: coolant in a 12

The service manager at the Buick agency where we had our Buicks serviced explained that Buick the straight eight mufflers (circa 1940’s) were designed to provide a slight back pressure of about 8 psi. When this back pressure dropped so did the performance of the engine. On our 1948 Roadmaster with Dyna-Flow, when the muffler got loud and the back prssure was lost engine performance was degraded. When an new muffler was installed, the problem went away. I don’t know if the current after market mufflers incorporate this deisgn feature, however, it is something to take into consideration in using a Buick muffler on a Pierce-Arrow.