372 Muffler Mod..............

[BostonBull]

I am going to be putting an unlimited coil, BB kit, and I will be doing a muffler mod to a 372 this week.

The Muff Mod will be nothing fancy. I want to put a hole dead center in the front and tack a screen over it.

What is the PERFECT size hole to drill if I will be using just ONE hole?

And where approximately should this be on a tach? 13,800? I want to get it rough with the tach and then I will tune it to the four stroke burble line.

 

[Cut4fun]

Here is one from a 359 to give you a idea. I have seen then with and without spark screen over the hole also.

 

[BostonBull]

That looks to be a slightly oblong hole maybe 1/2" by 5/8"? Or is it smaller?

 

[04ultra]

Here is a 372 that Crofter posted in another thread...




You can also check out this thread

http://www.arboristsite.com/showthread.php?t=36541&highlight=372+muffler+mod


.

 

[BostonBull]

Thanks good thread!

I am thinking about a 3/4" hole between the bracket bolts with a screen.

Is there anything inside the 372 muffle that needs to be gutted?

 

[joesawer]

Nothing inside the muffler to remove.
I put an extra port on the top of my 372 mufflers in front of the stock one with a shroud to direct the exhaust out the front.

 

[Kneejerk Bombas]

I'd sneak up on it.
Get the saw set up the way you want, except the muffler mod, maybe even run a few tanks through it. Then do some timed cuts, enlarge the hole and re-tune, do more timed cuts, enlarge the hole and re-tune, and repeat until the power flattens out or starts to diminish. Then add the screen and you're good to go. Even if you pass the optimal size, the screen will bring the flow back down.
Any other way is just guessing.

 

[trimmmed]

Nothing inside the muffler to remove.
I put an extra port on the top of my 372 mufflers in front of the stock one with a shroud to direct the exhaust out the front.

I have one like that and 2 with a front hole, my ears much prefer the extra port on the top, fwiw Aside from the noise factor, the front hole can make the saw a fire breathing dragon enough to light stuff on fire and you need to watch that particularly when everything is dry and crispy

 

[Crofter]

I'd sneak up on it.
Any other way is just guessing.

Good advice Mike! How much the saw is modded will make a difference too, in optimal size. A stock saw just wont need (or benefit from) larger than necessary and negative idle performance, noise and fuel use will be a result. Timberwolf did experiments to find max performance on highly modded saws and you start to get other tradeoffs long before you reach that point.
The maximum exhaust temperature from an opened muffler is much hotter than from a stock muffler.