Exhaust Systems

[12]

Does anyone have any experience, or pros/cons on the following on a 403
engine: (using stock cast iron manifolds, I don't want to use headers)

1. 3" systems vs stock 2 1/4"?
2. Does the carburator have to be re calibrated if you change from
a stock system to a 3" system?
3. Stainless steel vs aluminized metal?
4. One piece pipe from the "Y" vs 2 pieces joined (clamped or welded)?
5. Stock or flow thru mufflers?
6. Does the upgrade in cost over a stock system pay for itself in
peformance, or in any other way?

Thoughts and comments will be appreciated

Harold
9675.0203

 

[1]

Harold

I love the questions. I too will would like to see the answers.

Take Care
Arch

 

[zachary zehnacker]

We added a 3" exhaust with headers to our GMC for increased towing
power.

1. 3" systems vs stock 2 1/4"?

3" system is much louder than stock system it replaced. Dynomax
mufflers were not bad, but had one spot in the RPM range that was very loud.
These mufflers, however, actually pulsated from the amount of air going
through them and eventually wore out. We replaced them with Flowmasters
which are loud throughout the RPM range. These are built like tanks and
would probably last forever, but we will be replacing them soon to quite it down.
We are also considering adding in a cross-over pipe before the mufflers to
equalize the pressure.

2. Does the carburator have to be re calibrated if you change from
a stock system to a 3" system?

I don't remember having to change anything after this swap.

3. Stainless steel vs aluminized metal?

Our aluminized metal system is beginning to rust in some spots. The
stainless was not offered when we got our system, and we are thinking about
changing it over to stainless this winter.

4. One piece pipe from the "Y" vs 2 pieces joined (clamped or welded)?

Not sure.

5. Stock or flow thru mufflers?

I would suggest trying to find stock-like mufflers in the larger size to keep down
the noise levels.

6. Does the upgrade in cost over a stock system pay for itself in
peformance, or in any other way?

The power was increased in our 455, and the towing gas mileage increased
(we tow a 10,000 pound trailer). The non-towing gas mileage actually seemed
to decrease, however since most of our driving is with the trailer, we do not
really have enough data to verify it.

Zachary Zehnacker
Seemann Bros. Racing