346 porting

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khaas

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Was given a 353 to me by a friend that had a cylinder. No interest in saving the old one. There is a highway 45 mm kit on eBay I plan to buy. Going to delete the base gasket as well as put a 288 muffler on it. Right on here somewhere that a prior user head shaved a couple millimeters off the exhaust Port sides and a millimeter or two off the intake as well. Anything else worthwhile? Would it be worth it to advance the ignition a little bit?
 
What advantage is the 288 muffler addition?
Assuming (I have not tried it but can attempt) it actually fits in without contacting the top cover and or case.
The 346 and 353 have an internal pipe that terminates inside the chamber. Not really a possibility of a straight-through design. The 288 will have a straight through exhaust setup
 
Oh- okay.
Make sure to take plenty of photos.
Since you're interested here it is. Not easy to tell with the pictures but I'll try to explain it as best as possible. Once the exhaust leaves a cylinder and goes into the muffler there are two chambers. The chamber farthest from the cylinder must be accessed by the exhaust gases through various holes in the wall. After the exhaust goes through the wall it enters the tube which then travels up and out the top of the exhaust. You can kind of see the tube on the left side of the muffler inside
IMG_20240101_144908.jpg
 
Easy way to tell the 353 open port cylinder from a 346 closed Port cylinder is the 353 has these access panels bolted to the sideIMG_20240101_144929.jpg
 
Notice daylight coming through the exhaust outlet and this aftermarket 288 muffler. Straight throughScreenshot_20240101-145338.png
 
Nope not yet. I read on here it's a replacement for the 346 though. I'll update when I get it probably be a couple weeks

Read it on here- must be true then.
Will be most interesting to see how you make it work.
 
The 346 and 353 have an internal pipe that terminates inside the chamber. Not really a possibility of a straight-through design. The 288 will have a straight through exhaust setup
I dont think the 288xp muffler will work. The holes on the 346 are stagged and the 288 are not. However, the 288 muffler deflector is often used when muffler modding.
Every 346xp I have had has a hollow muffler with a top outlet. The 353's often have CAT mufflers that are plugged up.
 
I dont think the 288xp muffler will work. The holes on the 346 are stagged and the 288 are not. However, the 288 muffler deflector is often used when muffler modding.
Every 346xp I have had has a hollow muffler with a top outlet. The 353's often have CAT mufflers that are plugged up.

Party pooper- I was waiting for the DAMMIT posts in a couple of weeks. :laugh:
And yes- I am pretty sure the 288 deflector use is where the confusion is entering and there are MANY options for a straight through 346 type mufflers in the same kind of knock off aftermarket avenues the 288 one was coming from.
 
I dont think the 288xp muffler will work. The holes on the 346 are stagged and the 288 are not. However, the 288 muffler deflector is often used when muffler modding.
Every 346xp I have had has a hollow muffler with a top outlet. The 353's often have CAT mufflers that are plugged up.
I think you're right I may have been mistaken I think it's just the deflector that's used
 
The only 346 style muffler that isn’t mostly hollow is the 2152c or late 353 Etec. And the 353 cylinder pic you posted is actually closed port. It’s the earlier 350/351 cylinder that was open port.

The Hiway 45mm cylinder won’t make any more power than the one you have. I’d save up $10 more and buy an oem 44.3mm 346 cylinder
 

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