Not so Sally saw...

[Red97]

Hmm

.023 squish no gasket.

Everything bout this jug seems really close to where I wanted to go..

Maybe just clip the lower transfers, square up the intake a bit. An leave it be.

Thinking this may be like that one jug you found for you 066/64 @jmssaws ? Just right from the factory with a simple muffler mod...

 

[srcarr52]

Thanks for the info

Without a gasket this jug was 100,119,77

Vs the 104,121,77

Seems this saw may benifit from squaring the intake/exhaust durations. Keeping 18/19 blowdown..

Am I way off from your experience?

Guy plans on running a 3/8 36" as a big bar.

100,119,77 all those numbers are long, you may want to double check your degree wheel measurements and make sure you are not reading a lot of the port bevel.

104,121,77 is much closer to what I've measured on stock cylinders before.

Stock, without gasket (0.027" squish) I've measured them at 106,136,75. That was done by measuring the port height in the bore and back calculating the opening angle with the equations given in Bell's book, so you can't get any more accurate than that.

 

[jmssaws]

My notes show 103 to 104 on stock ones.

Be a *s-word load of grinding cutting 050 from the chamber,

 

[Mastermind]

I just take .025" from the 395, but like Shaun said, exhaust height can lower compression a bunch.

 

[Red97]

That is what is confusing me. I checked/double checked the wheel numbers. Stayed consistent.

I'm gonna take .020 off the base and re set squish.

99-100 on ex 118-120 tr probably 80ish on the intake.

Well see what it does.

 

[Mastermind]

Run a ring up in the bore to double check the numbers Joe.

 

[srcarr52]

My notes show 103 to 104 on stock ones.

Be a *s-word load of grinding cutting 050 from the chamber,

You can't be afraid of grinding if you want to go fast.

 

[jmssaws]

You can't be afraid of grinding if you want to go fast.

Preaching to the quire my freind

 

[jmssaws]

This 395 ran over 2 months falling before it hung. That's why I say be careful widening the exhaust. This was 5+ years ago before they dropped prices

 

[paragonbuilder]

This 395 ran over 2 months falling before it hung. That's why I say be careful widening the exhaust. This was 5+ years ago before they dropped prices
View attachment 37189

Ouch. That had to hurt!


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[jmssaws]

Ouch. That had to hurt!


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Not as bad as the 394 did a few months later.

 

[srcarr52]

This 395 ran over 2 months falling before it hung. That's why I say be careful widening the exhaust. This was 5+ years ago before they dropped prices
View attachment 37189

Too flat, not enough corner radius.

 

[czar800]

 

[jmssaws]

Too flat, not enough corner radius.

Live and learn

 

[paragonbuilder]

Too flat, not enough corner radius.

So what is "too flat"? How far is too far?


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[Mastermind]

He's saying the roof seems too flat. The corners too tight rather than just too wide.

I've done the same thing........easy to do.

 

[paragonbuilder]

He's saying the roof seems too flat. The corners too tight rather than just too wide.

I've done the same thing........easy to do.

I guess what I'm asking is how to know how far you can take it safely? How much it needs to be arched?


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[Mastermind]

I guess what I'm asking is how to know how far you can take it safely? How much it needs to be arched?


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I've done exhaust ports over 70% of the bore without issues. Shape is everything at that width. On a real life worksaw though......I use 65% as a max width.

 

[srcarr52]

He's saying the roof seems too flat. The corners too tight rather than just too wide.

I've done the same thing........easy to do.

We've all been there.

 

[Red97]

I guess what I'm asking is how to know how far you can take it safely? How much it needs to be arched?


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You can go as wide as you want/piston allows if you have enough arch.

But the port might not flow any better than a square 60%.

Another thing is the symmetry to the arch, it it is not very symmetrical the ring will rock back/fourth eventually freeing the pin. More so with extremely wide ports 70%+.

I probably use more arch than most, but I haven't Tryed to find out how far I can push before things start hanging...