346 porting (first time)

[paragonbuilder]

Not usually. If the blowdown is too long you lose power all around. You can try it where it's at first then raise them and see the difference.

I think I will do that. Sounds like a win all around though.

What makes a dolmar like so much blowdown?


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[mdavlee]

I think I will do that. Sounds like a win all around though.

What makes a dolmar like so much blowdown?


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Case capacity is all I can think.

Here's the one with the numbers I give you. It was running 18" .325" I'm pretty sure.

 

[Stihlbro]

This is a awesome thread!!!

 

[David Young]

Rod length.

You can measure the wrist pin and big end do some mathing and find center to center rod length

Or


Measure center to center of the rod with some calipers. Eye ball for best guess. Even if you are off 2 mm on the rod. It will minimally effect the reading.


@drf255

Al how do you know you are getting a true reading with the degree wheel? Wasn't there are thread where a gentleman showed. How you could get different readings with a wheel?

I will share an experience with you all a friend of mine here was looking for a 242 jug. So I helped him out. I measured and calculated port opening. He shared with me his stock measurement with a degree wheel. Our numbers were within a half a degree in every port.


let's have some fun with this and see if it's bs or not.

David

 

[drf256]

I'd still use a degree wheel Dan.

I'm intrigued by David's post. I certainly may use it to calculate and cut card stock, but I'd still double check it with a wheel.

The relationship is so non-linear that I don't think I'd trust it without double checking it.

Who knows, it may prove to be just as exact.

Rod length.

You can measure the wrist pin and big end do some mathing and find center to center rod length

Or


Measure center to center of the rod with some calipers. Eye ball for best guess. Even if you are off 2 mm on the rod. It will minimally effect the reading.


@drf255

Al how do you know you are getting a true reading with the degree wheel? Wasn't there are thread where a gentleman showed. How you could get different readings with a wheel?

I will share an experience with you all a friend of mine here was looking for a 242 jug. So I helped him out. I measured and calculated port opening. He shared with me his stock measurement with a degree wheel. Our numbers were within a half a degree in every port.


let's have some fun with this and see if it's bs or not.

David

I have no idea. I find it all fascinating and easier than a wheel if its on the money.

It may be more exact on an exhaust roof than a wheel.

Whats the third constant it wants, the angle. How does one calculate that.

 

[Ironworker]

I have no idea. I find it all fascinating and easier than a wheel if its on the money.

It may be more exact on an exhaust roof than a wheel.

Whats the third constant it wants, the angle. How does one calculate that.

If you go to the site and punch in your numbers it will give you the option of piston and crank angle.

 

[drf256]

I think the angle is the degree at distance (now that I look at it)

No?

This reminds me of Brix calculation for final gravity instead of using a hydrometer. Was close enough for homebrewing.

 

[paragonbuilder]

I have no idea. I find it all fascinating and easier than a wheel if its on the money.

It may be more exact on an exhaust roof than a wheel.

Whats the third constant it wants, the angle. How does one calculate that.

Constants are stroke and rod length. Then you can input degrees wanted and find your measurement off the squish band. Or input your measurement off squish band and calculate degrees.
Should be pretty easy to check a few jugs both ways and see how accurate. I would say the math is probably just as accurate as long as we can be accurate with our measurements. But the degree wheel is also subjective to human error.


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[paragonbuilder]

And if you use this method don't forget the measurement is really off the top of piston. So your squish measurement must be added or subtracted depending what you are figuring.


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[Gypo Logger]

Randy built me a 346 jug Flawless work. there is much more power to be had out of it than I can get, as I cant lean it out enough. I think this is a carb prob. What's the biggest stock carb can I put on it? never had much luck with a 359 carb on a 346

 

[Ironworker]

Randy built me a 346 jug Flawless work. there is much more power to be had out of it than I can get, as I cant lean it out enough. I think this is a carb prob. What's the biggest stock carb can I put on it? never had much luck with a 359 carb on a 346

I feel the same way, I just bought a walbro 191 I'm gonna put on and try.

 

[MG2186]

199 is the best


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[Tor R]

199 is the best

thank goodness I have 5 of them to my projects

 

[David Young]

You are a rat bastard and it is not fair !

 

[MG2186]

You are a rat bastard and it is not fair !

I also have 5 of them.... Lol


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[David Young]

You!

I have a potty mouth

 

[paragonbuilder]

Well I was going to start putting her back together and this caught my eye.

So I looked closer and this.

Looks like someone started trying to separate the cases with a screwdriver.
And crushed a fuel line.
Looks like I need to examine closer.


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[Gypo Logger]

I also have 5 of them.... Lol


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I hate you guys, I only have four!

 

[Gypo Logger]

199 is the best


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Is there an after market 199, or do I have to buy an OEM that was made in China? Lol

 

[Tor R]

Is there an after market 199, or do I have to buy an OEM that was made in China? Lol

I've only seen those Genuine Walbro 198-1 on ebay, dunno if they are made in China