460 and 660 work saws double build

timberwolf

timberwolf

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Have two new in the box saws to build, one 460, one 660. Building them both much the same as solid work saws. Figgured it would be interesting to do them at the same time just to compare.

A real treat having two new in the box saws to build. Wish they were mine, but they belong to a member here.
 
timberwolf

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Here are a few pics with the covers off.

460 surprised me with 172 psi compression.
Squish 0.032
RPM 13,800 16 inch bar and chain
Head Volume 8.2 cc

660 I could not get over 150 psi compression.
Squish 0.029
RPM 13,100 same bar and chain
Head Volume 10.0 cc
 
timberwolf

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Cut times with off the roll Oregon square chisel 460 in 14.5 inch hard dry frozen poplar 7.10 seconds. 660 cut in 6.19 seconds. Same bar and chain. Was pushing pretty hard on both but harder with 660.

I'l try to get video up later.

Few more pics.
 
romeo

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Doing up new saws is nice. Your not wasting your time on filth, striped bolts, and broken pieces.

Brian, while you have those jugs off, what is the measurement from the combustion chamber to the base on both (for my little black book)?
 
timberwolf

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Which measurments you looking for? Reread, 72.27mm base to squish on 460 and 80.98mm 660.

Different piston in this 660 to what I have seen before. Nice big windows and a little more support for the skirts. Too bad they didn't make the skirt a few mm wider while they were at it.

I'll get to measuring port timing ect.
 
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romeo

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Which measurments you looking for? Reread, 72.27mm base to squish on 460 and 80.98mm 660.

Different piston in this 660 to what I have seen before. Nice big windows and a little more support for the skirts. Too bad they didn't make the skirt a few mm wider while they were at it.

I'll get to measuring port timing ect.

That was the measurement I was looking for. Those aren't even close, 8mm is a big difference.
 
timberwolf

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Can't be for case clearance, the skirts are the same width and profile at the bottom. Only thing I can is is to add support area esp on intake skirt. The bulge in the skirt is worked into the lower support to the pin boss, so would add a lot to strength, taking load off the skirt.

Pistons are same height and pin location is the same.
 
Metals406

Metals406

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Can't be for case clearance, the skirts are the same width and profile at the bottom. Only thing I can is is to add support area esp on intake skirt. The bulge in the skirt is worked into the lower support to the pin boss, so would add a lot to strength, taking load off the skirt.

Pistons are same height and pin location is the same.

Hmmm... You would think it would be the same on both pistons? Unless Stihl noticed the skirt was too weak at the bottom of the skirt for the 660?

Have there been 066/660 failures at the bosses in the past?
 
timberwolf

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Not aware of mechanical piston failures, but worn skirts on the intake side. More surface area is certainly going to help spread the load.

Intake port on 660/066 is quite high and piston quite short and compound that with narrow skirt and there is very little support on the intake side of the skirt while the intake port is partially open.
 
Metals406

Metals406

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Not aware of mechanical piston failures, but worn skirts on the intake side. More surface area is certainly going to help spread the load.

Intake port on 660/066 is quite high and piston quite short and compound that with narrow skirt and there is very little support on the intake side of the skirt while the intake port is partially open.

So, how much higher is the intake than an earlier 066?
 
timberwolf

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I'll try to get some port maps done late, but intake port is ~ 20mm high top to bottom which is roughly the distance from the pin center to the bottom of the skirt. I have seen nwer 440s with same bulged skirt piston design, just first time I saw it in 660.
 
timberwolf

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Here are the port maps, did not scan the best, but gives the idea. Amazing, intake and exhaust ports on 460 are wider than 660 by quite a bit.

It's going to be harder to find gains on the 460 than the 660. CC for CC the 460 did better in cut times, makes sense, more compression and more port width.

Will figgure out the port durrations next.
 
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timberwolf

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Port Durrations:

460

Exhaust 160.0 deg
Inatake 144.0 deg
Transfers exhaust side 112.6 deg
Transfers intake side 121.6 deg

660


Exhaust 180.8 deg
Intake 153.4 deg
Transfers exhaust side 116.6 deg
Transfers intake side 123.0 deg

These two saws stock are ported very differently.
 
timberwolf

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Here is the undersides of the pistons cleans up. Nothing radical, just improving flow where possible without hurting strength. Opened up the windows a hair but on this new 660 piston there is not much room to make them bigger.
 
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timberwolf

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What Happened to Stihl Quality?

Likely going to take some lashes for saying this, but Stihl's quality on the cylinders has gone way down.

There are all sorts of humps and bumps, blobs of casting and ridges on the port edges. Seen beter porting in aftermarket jugs. Also on the 660 jug the porting on exhaust is about 10 deg longer than I would like to see and the plating and machieling in the top 1/8 of an inch is very poor. I'd like to be able to mill the squish and lower the jug, but plating just want allow for that. If you have any original 066 jugs hang on to them the 660's are junk in comparison.

Pics of the ports, machiening on of the pistons and final pistons. On the intake pic it's not super clear, but there is a ridge at the edge of the port about 1mm high running from one side to the other.
 
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