Differing size pipes make much difference?

Dad's Pontiac wagon responds very well to exhaust flow (thanks for mentioning all of our earlier testing Duster 340).

Here it is with the big Goerlichs on about a year ago or so.

[ame="http://www.youtube.com/watch?v=cu4I6gfF68w&playnext=1&list=PL0024231A86C1C0C5"]YouTube - ‪71 LeMans Station Wagon at Strip, Run #9, 11.56 at 115+ mph‬‏[/ame]
[ame="http://www.youtube.com/watch?v=Ta6kP3itZx8&feature=BFa&list=PL0024231A86C1C0C5&index=3"]YouTube - ‪71 LeMans Station Wagon at Strip, Run #7, 11.60 at 115 + mph‬‏[/ame]

Dad is still playing with mufflers even today. He has been running the 3.0" Dynomax VTs with short tailpipes and doing so to see if the weight difference affected the performance much. It has been running 11.40s at 117.5 with them or the 2.5" Dynomax UltraFlos with 2.5" tailpipes on his 4100 pound car with the 474 cu. in. Pontiac engine. His mufflers are way to the back so again, we found it was not affected as much by pipe size just like running 2.5" ones on the 340s when compared to 3.0" ones. Granted, a big cubic inch engine or a little one running at high rpm will be more sensitive to this but in the grand scheme of things, the smaller tailpipes do not hurt as much as we used to think they might.

Tom Hand