346 porting (first time)

[Redfin]

Hey Dan, your work is looking great. Very nice snag on the foredom and bits. When you do get a degree wheel, just for reference i bought a 7" off amazon and i need to sit the saw on a block so the wheel doesnt hit the bench. Just something to think about it you want a larger wheel.

 

[Mattyo]

nice job Dan!

 

[David Young]

David,
I don't have a degree wheel yet. Are you asking me to measure actual distance from squish band to exhaust and transfers?
Squish was .017 with no sealant or gasket.

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No I was not giving you a hard time I was trying to share something with you. There is another way to find port openings and durations without a wheel. If you provide what I asked I will give you your durations. I believe this method is more accurate. Just trying to be helpful.

David

 

[sunfish]

Lookin good, man! It'll be a runner for sure.

 

[ft. churchill]

No I was not giving you a hard time I was trying to share something with you. There is another way to find port openings and durations without a wheel. If you provide what I asked I will give you your durations. I believe this method is more accurate. Just trying to be helpful.

David

A guy I work with is a long time two stroke porter from the 70's and 80's. He also uses the measurement method. More than one way to skin a cat.

 

[mt.stalker]

No I was not giving you a hard time I was trying to share something with you. There is another way to find port openings and durations without a wheel. If you provide what I asked I will give you your durations. I believe this method is more accurate. Just trying to be helpful.

David

Could you explain/demonstrate the measurement method for those here who may want to learn it ?

 

[David Young]

Could you explain/demonstrate the measurement method for those here who may want to learn it ?

I was planning on doing a thread on this but I guess here is as good as any. I'll try to explain it.

you need the stroke length. in this case of the 346 saws it is 32.5mm

you need the con rod length and it doesn't have to be perfect on these saws it is 60 mm

you need to know the squish and subtract that from your port opening measurement lets just say we will set it to 20 thou or .5mm

stock transfer numbers for a 346ne around 125atdc

Many people move them to 120 atdc.

you can go both ways port open to distance or distance to port open.

here is a 125 atdc open.

So on a stock saw with 20 thou squish the transfers will be 27.566mm down from the squish band

 

[David Young]

if you want to go the other way select crank angle instead of piston position and put your linear measurement in.

 

[David Young]

I think it is a heck of a lot easier and faster than a degree wheel. Timberwolf turned me on to this idea. Of course he would take it to the next level and do a port map and figure the timearea of each and bd time area.

 

[David Young]

 

[David Young]

here is what I had on a 353 jug lately and I wanted to go to 123.

 

[paragonbuilder]

No I was not giving you a hard time I was trying to share something with you. There is another way to find port openings and durations without a wheel. If you provide what I asked I will give you your durations. I believe this method is more accurate. Just trying to be helpful.

David

Very cool! I will measure tonight and let you know. I'd love to learn a different way!


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[David Young]

so here is my measurement I add my squish measurement set my ring down to that line a mark it.

 

[Tor R]

@David Young, could you please make a thread in technical area about this, step by step.

Your idea is awesome, and it may make it far easier for dummies like me to start to port.

 

[David Young]

I certainly will please be patient with me I'll get some pics n stuff. Thank you.

 

[redoakneck]

Very cool!!!

 

[Ironworker]

That's pretty cool David Young, looking foward to a thread on this, take your time I'm sure it will be very informative.

 

[paragonbuilder]

David let me know if I did this right.
So here are my measurements in mm.
Exhaust 23.25
Intake 51.5
Transfers 27.5 exhaust side 27.2 intake side.
I need to verify squish but with sealant it should be just under .5 but I'll use this for now.
So my exhaust is 105.81

Intake is measured from the bottom of the piston so I subtracted .5 squish and 37 for the height of the piston.
It came to 74.55

Exhaust side transfers 124.66

Intake side transfers 123.16

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[David Young]

Yeah brother you nailed it the intake is the toughest to explain and you did it well. Nice job dude!

 

[paragonbuilder]

Yeah brother you nailed it the intake is the toughest to explain and you did it well. Nice job dude!

Thanks!
So to sum up my numbers are
Exhaust 105.81
Intake 74.55
Transfers 124.66/123.16

How do they look for you 346 builders?


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