[vatdevil]

Originally Posted by Dana E.

I'm using a set of polished stainless side pipes from GAS-N. Unfortunately it looks like he may no longer be in the side pipe business, which is unfortunate because the pipes are gorgeous, work, and at around $1500, were a good deal.

I've had three sets of side pipes on my SPF so far: the stock SPF pipes, a set of GAS-N pipes with a 2" core and finally, a set of GAS-N pipes with a 2.5" core. The factory pipes and the 2" core GAS-N pipes were fairly quiet and the GAS-N 2" core pipes had a nice "crackle" to the sound. The 2.5" GAS-N pipes have more of a deep "rumble" to the sound.

I also tested the SPF headers/side pipes and the SPF headers/2" core GAS-N side pipes on the dyno with my 427 SBF. Compared to the stepped 1 5/8" to 1 3/4" dyno headers with no mufflers, what I found, at the 500 HP level, was the factory SPF exhaust system cost something like 20 HP at the peak (5900 RPM). The 2" core GAS-N pipes were right up there with the larger flowpath SPF mufflers. These are the results I saw with my tests. I did not test the 2 1/2" GAS-N pipes on the dyno.

Maybe I got the freak set of factory pipes that don't cost a bunch of power. I doubt it, but if so, I should sell them at a premium price!

Does my car run any better with the larger core mufflers? I can't tell-I seem to have a traction problem with whatever muffler is on the car. I do think the 2 1/2" core pipes are easier on the ears compared to the 2" pipes. I do know that loud does not always equal more power.

20 HP gain matches up with what others have posted on a 427 SB. On my 351, larger muffler HP gain was almost nils on the dyno. Actually lost some down low.