I have a 384CI LS1 with the usual bolt-ons, a mild 230/234 cam and pretty good heads.

My exhaust is pretty typical, 1 3/4 headers into 3" mandrel piping TO THE MUFFLER. I absolutely hated the exhaust noise, so I reinstalled the stock muffler. I hate cutouts as I have yet to find ONE that doesn't leak (regardless of all of the company claims that they don't).

As it exists, all of that piping is held back by a downsized pipe through a stock muffler. Any guesses as to what kind of power I am leaving on the table by not going high flow or a cut-out?

 

on that setup...15hp is a good guess...could be 20

quite of few times people have dynoed 15hp gains with a cutout on a stock engine and exhaust. so behind a cammed stroker it would be that much more noticable.


i had an old manual cutout and it didn't appear to leak, at least not enough to hear over the regular exhaust noise.

now the electric c/o's....yeah i've heard them leak

 

Like mentioned above, I think a solid 15-20 is probably killed by the stock muffler on a 383c.i. motor. It's enough to where I would be looking for a catback to put on it. If you are concerned with leaks, have an exhaust shop weld it up after you get it clamped where you want it.

Jon

 

Go with the Borla ProXS Mufflers they are the quietest and the most powerfull. Makes more HP than the cutouts.

 

I think 35 rwhp and rwtq on my setup https://ls1tech.com/forums/dynamomet...-en-close.html

on yours maybe less .... 20-25 maybe?