Replacing the muffler

[Unregistered]

I have a 100% Stainless muffler from an old corvette. It has no packing and is perfectly sound (no pun ntended).

It is significantly larger than the stock muffler, but still fits into my space.

Can anyone think of any reason why this might not work?

Since the muffler is larger, the water column through which the exhaust is forced is taller (deeper?) by about a factor of two.
My college physics tells me that this requires more force to lift out, and thus the back-pressure would be higher.

Would a higher manifold pressure be a problem?

-Kevin Cook
Gloucester, MA

[Jim Booth]

Seems like higher pressure would make the no-start-water-in-the-cylinder problem worse. Pumping the water higher will take more power, but maybe that isn't worth bothering about. Can you tilt the muffler to keep the vertical distance the same? If it's stainless you could have it cut and rewelded the proper length.

Jim

[gloucestersailor]

The backpressure cited in the moyer overhaul guide is 1-1.5 psi.

I think the new muffler won't work. Here are two arguments against it.

Argument 1:
The water column in the standard muffler is about 4 inches. If the water column in new muffler is twice the height, the pressure required to lift the new water column will be twice as great. That's a 100% increase in pressure. If the A4 backpressure averages 1.25psi plus or minus .25psi that converts to a 20% tolerance. So the new muffler won't work because the backpressure can vary by 20% but the new muffler causes a 100% variation.

Argument 2:
The actual force required to lift the water in the standard muffler (in this case) is the weight of the water. The diameter of a stock muffler is about 1.75" which translates to about .3lbs over the 4 inch water column. A backpressure of 1psi could lift .4 lbs of water in a water column of this diameter. (1.5psi could lift .6lbs in the same tube). If the new muffler has an identical water column diameter (which I'm sure it does not!) the fact that it is twice the height means there is twice the weight of water. Being most conservative and assuming that the backpressure in this particular engine is 1.5psi, this means that the engine could just barely push out the water in the new muffler. If the new muffler is even fractionally larger in diameter, the backpressure would be increased past tolerance. I wouldn't like being borderline.
(Also note that I rounded all my values in order to give the new muffler a fighting chance)

In any case. Stick with the old muffler, or replace it with one that has a similar water column.