[Ant]

I have seen multiple small diameter perf cores welded into a group fitted to race cars eg. if you have a 3" internal diameter muffler you can fit inside a group of 4 x 1.25" cores which run the length the muffler, a leading motorsport team claims this can reduce noise significantly and possibly up to 60% but I guess that varies and as mentioned in this post high compression is very hard to muffle!

I am going through a similar scenario with my 373 based cup engine and deciding on either 4 or 4.5" diameter outer case, and whether to use 3" or larger 3-1/2" internal perf core, I have the stainless screen material to make my own extra muffling cores. I notice on Vintage Motorsports cobras they use 3" turnouts which I think look better than the 3.5" drainpipes most people use, but I guess if you need a large core you dont need to restrict the end of the pipe.............!