Stihl 660

[Allen Miller]

Are you talking about a piston with 2 height changes?

Yes

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[Bigmac]

The epoxy works great! You don’t want to permanently cut a notch in your piston to make port timing adjustments, it is ok to test a change without grinding but it will effect your squish and create a bad burn. What are you trying it get out of this, you may be better off starting over? What didn’t you like about the original numbers?

 

[Allen Miller]

The epoxy works great! You don’t want to permanently cut a notch in your piston to make port timing adjustments, it is ok to test a change without grinding but it will effect your squish and create a bad burn. What are you trying it get out of this, you may be better off starting over? What didn’t you like about the original numbers?

I was trying to 100/80/120 all the reading I've done seems like there all over the place. Not trying to make a lot more rpm just a lot more torque . I have gotten 102/84/117 and .018 Squish. Seems like you have experience here what # do you suggest. Thanks

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[brshephard]

You want more torque, raise the intake.
At 78 degrees you will have identical exhaust and intake duration.

In general, a shorter duration gives torque. (Numerically higher exhaust, numerically lower intake)

I did 102/122/78 with a Cross cylinder. It makes some torque.

 

[Bigmac]

When I cut 40 out of the squish band I got 100/132-135/87 I wanted torque as well, I epoxy the intake to 80-81 and raised the transfers to 127-125, I might go back in and play with it some more, raise the transfers, but I need more trigger time on it. I ended up with 200psi and it sill starts easy, with timing advanced.

 

[Moparmyway]

I was trying to 100/80/120 all the reading I've done seems like there all over the place. Not trying to make a lot more rpm just a lot more torque . I have gotten 102/84/117 and .018 Squish. Seems like you have experience here what # do you suggest.

Raise the exhaust to 98 and try that. You might surprise yourself

 

[Allen Miller]

When I cut 40 out of the squish band I got 100/132-135/87 I wanted torque as well, I epoxy the intake to 80-81 and raised the transfers to 127-125, I might go back in and play with it some more, raise the transfers, but I need more trigger time on it. I ended up with 200psi and it sill starts easy, with timing advanced.

Ok I'll try that. Out of these 3 carburetor which is best performance 1st walbro wj 76b , 2nd wj 35A 3rd wj 69 with .074 jet . Been using wj 69 I installed the. 074 jet but don't really care for limiter caps. Also any good carb mods

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[MustangMike]

Always remove the limiters on the caps. If your saw "4 strokes" out of the cut, you are getting enough fuel.

 

[brshephard]

Raise the exhaust to 98 and try that. You might surprise yourself

What numbers do you like to run these saws at?

 

[Moparmyway]

What numbers do you like to run these saws at?

Ive ran 103 - 93 on exhaust

18-20 blowdown

Intake:
78 - 84

 

[MustangMike]

And ....

 

[brshephard]

Ive ran 103 - 93 on exhaust

18-20 blowdown

Intake:
78 - 84

Obviously you've done a lot of work with these saws.
Can you summarize your experience with different port work you tried.
What worked well and what didn't?

 

[Moparmyway]

Obviously you've done a lot of work with these saws.
Can you summarize your experience with different port work you tried.
What worked well and what didn't?

Exhaust doesn’t seem to be the most important number on the 1122’s .......... blowdown is.

Lately I just let the exhaust land wherever it ends up after machining. A great recipe for a no epoxy intake is to take 0.030 off the base, cut the chamber to set squish for no gasket, leave both the intake and exhaust where they land and raise the transferrs for blowdown. Cant go wrong with 20 degrees of blowdown, I’ve ran 18, and I’ve ran 22 depending on muffler configuration and intended use

 

[drf256]

I heard the rule was .100 minimum.
What happens if you break the rule?

I believe the crown starts to erode. At least that’s what I’ve been told.

Also, what Mr. Sausage Fingers said.

 

[Allen Miller]

Always remove the limiters on the caps. If your saw "4 strokes" out of the cut, you are getting enough fuel.

I done that . I cut the ends off when I got saw a couple years ago. I was wondering if there was any difference between carburetor. Just look at them only change on outside was limited caps. I did check the two older ones had the larger jet .

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[brshephard]

Exhaust doesn’t seem to be the most important number on the 1122’s .......... blowdown is.

Cant go wrong with 20 degrees of blowdown, I’ve ran 18, and I’ve ran 22 depending on muffler configuration and intended use

I appreciate you taking the time to share, I know that's some hard earned knowledge.

Can you expand more on the blowdown.
What situations would you want to shorten or lengthen?

 

[Moparmyway]

I appreciate you taking the time to share, I know that's some hard earned knowledge.

Can you expand more on the blowdown.
What situations would you want to shorten or lengthen?

A restricted exhaust will need more BD

Think time/area as well as what else is happening if you decide to increase blowdown ?

 

[MustangMike]

A restricted exhaust will need more BD

Wow, like you are throwing me a life line!!!

 

[brshephard]

A restricted exhaust will need more BD

Think time/area as well as what else is happening if you decide to increase blowdown ?

So you open up the stock muffler to get away with a shorter blowdown.
What keeps you from opening the muffler further and going to 16?
Maybe too much fuel out of the exhaust?
Lost case compression?

What situation did you decide to run 22?

 

[Moparmyway]

So you open up the stock muffler to get away with a shorter blowdown.
What keeps you from opening the muffler further and going to 16?
Maybe too much fuel out of the exhaust?
Lost case compression?

What situation did you decide to run 22?

I haven’t seen 17 bd any better than 18, even running no muffler

Primary compression is what must be considered, can’t gain primary compression without gaining BD