[Lee]

Here is a dyno test I did on a mild, low compression (less than 8.0:1) 455 with stock heads, with headers.

First test had 2.5" pipes from the headers to a set of 3" FlowMasters, then to 2.25" tailpipes.

Second test is full 3" pipe, 3" 14" case Borlas ProXS mufflers, to mandrel bent 3" tailpipes. There is a 2.5" H-pipe ahead of the mufflers. First pull this combo made more power across the tested range, but the AFR leaned out big time. The test shown is after going several steps smaller on the primary metering rods (Qjet).

[besserspat]

Originally Posted by Lee

Here is a dyno test I did on a mild, low compression (less than 8.0:1) 455 with stock heads, with headers.

First test had 2.5" pipes from the headers to a set of 3" FlowMasters, then to 2.25" tailpipes.

Second test is full 3" pipe, 3" 14" case Borlas ProXS mufflers, to mandrel bent 3" tailpipes. There is a 2.5" H-pipe ahead of the mufflers. First pull this combo made more power across the tested range, but the AFR leaned out big time. The test shown is after going several steps smaller on the primary metering rods (Qjet).

It would have been interesting to see the 3" system with 2.5 tailpipes. I initially wanted the full 3" on my own 73( 461 9.5CR 232 238 HR 260 SD CNC heads and 1 3/4" dougs but my other 2 cars with 3" are loud AF.

I was hoping to run 2.5 muffs and tailpipes after a 3" pypes X pipe.. just for sake of keeping the noise down and easier fitting tailpipes than the 3" .

I spray another 200 so the 3" tails may prove beneficial.

How do.you like the Borla XS and the 3" system .? How loud , drone? Etc..
The XS were my choice for 3" dur to their slim case design that gives good ground clearance for a 3" muffler.

Thanks
Peter