A couple muffler mod questions

[huskihl]

I was discussing this with my local shop owner the other day, he said he felt the mod was just making more noise unless you messed with porting and timing, he said he’s not an enthusiast of muffler mods, so he can’t say for sure, but I was asking in reference to my 385 which seemed to be getting tired.

A 385 gains about 1HP with a 3/4-1” muffler mod outlet added. 372 uses the same (or at least very similar and interchangeable) muffler and gains about 3/4 HP with the same mod.

 

[huskihl]

Couple pics of some that I’ve done

 

[guym3]

Have a look on Dyno Joes mods on youtube. He has taken each step in modifying a saw and dyno'd it to quantify the improvement. Most opening up MMds with a pipe outlet seem to add 3-5% up to an expansion chamber which can add 50%. I'd say most of mine have been 5% or better. Also run cooler and if you are porting fully then you won't get the full benefit without opening up the restrictive factory muffler.