372xp more power!

[huskydave]

I recently bought a 372xp and I want to mod the muffler at some point in the future. Which is better the open hole in line with the exhaust port or the two pipes coming out of each upper corner. I also have not read any dimmensions for the large hole type some look bigger than others, some are round and some oval. Which works best same goes for the two pipe method some use 3/8" tubing some use 1/2" which will have better results 80% of the port is also a little confusing how big is the port should I measure that with my vernier? I am a machinist and like to do things right the first time this is the reason for my post. I was also wondering if the ignition timing can be advanced from 0-13500 ie move pickups? or is the timing fixed I know it has a rev limiter.

 

[rbtree]

Best place for the port is on the side of the muffler. However, you can easily cut a hole in the muffler behind the flange bracket. Then you can add a screen and pressure will hold it in.

formula that works for many is to have the muffler exhaust ports 125-150% larger than the exhaust port opening at the cylinder. You'll reduce cut times by 20% or so. Be sure to adjust the carb.

 

[timberwolf]

For a stock saw upto 100% to 125% is going to give you most of the gains with the mildest side effects.

A chunk of playdo or plastasiene can be used to take an image of the exhaust flange, then you can measure it with calipers, or just simply measure the circumfirance at the port end with a piece of string.

Two pieces of 3/4 inch pipe should do fine.

Timing is fixed and there is no easy way to move the coil, However the flywheel can be rotated with some work to the shaft key.

 

[buck futter]

Timberwolf,

How much advance do 372's need?

 

[timberwolf]

Wish there was a simple answer, What fuel, what compression, which coil. Unless your doing something pretty drastic I don't think moving it is going to make any huge gains, maybe a little advance could get a bit in smaller wood.