346xp exhaust and blow down numbers.

[Apparition2]

CAUTION: I have read enough to be dangerous.

Well enough to know that I don't know. I am in the middle of the classic 345 to 346xp conversion.

It is my first porting and is on the first saw I bought new. A 2003 345 that I gave to my Son in Law for land clearing after I bought a 346xp. Poor thing is now on the shelf. Cleaned up really nice.

I bought a Warhawk 346xp cylinder to start my grinding adventure. I think the casting and plating look good.

I took 0.018" off the 350 cylinder base plate for a 0.020" squish.

The exhaust is at 105 ATDC.
Transfers are 128 ATDC
Intake is 74 BTDC
Blow down is 23 degrees.

I can probably come up with a way to raise the transfers but want to ask for a work saw running a 18-20" bar should I:

A. Leave the ports where they are
B. Raise the exhaust to 102 or so and have 26 blow down.
C.. Raise the exhaust and figure out a way to raise the transfers? Maybe 20 or so?

I probably should lay down on a couch and explain to someone why I feel the need to improve something that is probably good enough to start with.

 

[NSEric]

If it was mine I'd leave the exhaust at 105, raise the transfers to 120 and lower the intake to 77 or 78.
You can make the exhaust pretty wide so it dosnt need to be higher, 105 is a good number for a 346.

Blow down is weird and different for every different model, I dont worry about specific numbers and copy good running builds others have done.
My saws have anywhere from 15 to 28 degrees of blowdown, depending on the saw. As a rule smaller saws have less blow down.
The similar 346, 359 and 372 all like the transfers at 120 with the exhaust at 102-105 and the intake at about 78.

 

[Apparition2]

If it was mine I'd leave the exhaust at 105, raise the transfers to 120 and lower the intake to 77 or 78.
You can make the exhaust pretty wide so it dosnt need to be higher, 105 is a good number for a 346.

Blow down is weird and different for every different model, I dont worry about specific numbers and copy good running builds others have done.
My saws have anywhere from 15 to 28 degrees of blowdown, depending on the saw. As a rule smaller saws have less blow down.
The similar 346, 359 and 372 all like the transfers at 120 with the exhaust at 102-105 and the intake at about 78.

Thank you for the response!!!!

I have been obsessing and wanted an experienced opinion.

I will work on tools for the transfers. I have an NE 346 so I am really looking forward to comparing the two saws.

 

[Apparition2]

Will I gain anything by widening the intake?

The intake seems big enough. Intake is smallest at cylinder wall and is 263mm2. The opening in the carburator is 17mm round which is 227mm2.

 

[huskihl]

Will I gain anything by widening the intake?

The intake seems big enough. Intake is smallest at cylinder wall and is 263mm2. The opening in the carburator is 17mm round which is 227mm2.

I would widen and lower it a little bit. Compare the area of the carb end of the boot to the area of the port

 

[Apparition2]

Thanks guys! You have given me enough direction to finish this one. I really appreciate the help. It is hard to get years of experience when you are working on something for the first time.

Thanks!