ACrooks69

iTrader: (1)

I have them (4.5") on my 413 SBC and I'm dry to about 3" before the muffler. I got so used to them that I decided to take them off and see how effective they really were. Even I (who like things on the louder side) thought wow!, those things really did a lot. I put them back on when I got to the sand bar destination. My motor kicks out about 470 corrected HP and I had no effect on top speed (GPS). I think they will do a little with dry exhaust, but not nearly as much. I've also tried the Car chemistry inserts http://www.summitracing.com/parts/cci-3di03r/overview/ that are much like the GGB's and they did very little (sound meter verified). I never checked the Gibsons because it was so obvious they were a lot quieter,

tomas_wallin

I have a couple from my previous boat with clamp on 4.5 Gibson Bullets. 28 Pantera with blown 509 with dry SM Gen III dumping only a minimal amount of water at the tips providing just enough water to keep the Gibsons from getting discolored.

http://www.youtube.com/watch?v=0sF5myAxrKs

tomas_wallin

One more
http://www.youtube.com/watch?v=300rvhFNSXA

pstorti

iTrader: (2)

I have these on my boat http://gibsonperformance.com/product..._number=110001 I had the Imco clamp 4" clamp ons before these that have the eyebrow at the end. For my boat with the diesels the Imco's droned to much and they were to long and touched the drives with the wheel cranked over. The Gibsons are shorter, sound better, slightly quieter. I posted some pics on a post here somewhere.

Almost forgot no loss of perfomance with either one, but I only have 325hp each side, but all that HP does come out of one 4" pipe so maybe it is similar flow to a pair of 4" from a 525. My exhaust are wet.