066 Top End # ..... uh, whatever

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mtngun

mtngun

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If you have been following my other 066 threads, you know I ebayed a used 066 jug to replace the other disastrous top ends. A Meteor piston is also on the way.

Looks like Grande Dog will be sending me a 54mm NWP kit, too, to replace the funky BB kit, so that is also a very interesting possibility.

Meanwhile, let's take a look at this used jug and see how bad it is. It appears to be a recent 660 jug, not 066. The bore seems great, no scratches or pits.

Port maps, old OEM on top, new-to-me OEM on bottom. Sorry for the fuzzy pic, but you can still read it. Pretty much the same port timing and shapes, except the newer jug has a shorter exhaust port.
attachment.php


Let's pretend this jug is installed in a stock saw, with the typical 0.025" squish. Here's the resulting port timing, using the calculator at modelenginenews.com.

Exhaust opens: 93.5° ATDC
Exhaust closes: 86.5° ABDC
Exhaust duration: 173.0° :mad:

Transfer opens: 115.0° ATDC
Transfer closes: 65.0° ABDC
Transfer duration: 130.0°

Inlet opens: 100.5° ABDC
Inlet closes: 79.5° ATDC
Inlet duration: 159.0°

Blowdown period: 21.5°

OK, so the port timing is terrible, at least for milling.

The zero-squish chamber volume is 10cc. My old OEM jug was 9.5cc, so the new jug is worse. Insert your favorite swear words here. :censored:

Well, what's a guy going to do (besides switch to a different brand of saw) ?

Buying used 066 jugs is a crap shoot. You might get lucky and get a jug with good timing and compression, or not.

Buying new 660 jugs -- well, I've only heard bad things about the new 660 jugs. Besides, I can't afford a new 660 jug.

Too bad one of the aftermarket makers doesn't step up to the plate with an 066 P&C kit that has sane port timing and a smaller chamber volume, hint, hint. :)

I'll won't do anything with this jug until I have a chance to inspect the NWP. I'll install whichever jug has better specs, but I'm guessing they will be two peas in a pod.
 
blsnelling said:
That exhaust and transfer port timing is crazy high. I've never seen anything like that. I'd be real interested in seeing you bolt it up and putting a degree wheel on it.
Click to expand...
Pretty much the same timing as Martinm210's 660 jug.
stihl066stocktimingve4.png


I plan to degree it if and when it goes on the saw. I guess I could do that tonight with an old scrap piston. So far my port map calcs have been within 2 degrees of the degree wheel for intake and exhaust. One time the blowdown number was 5 degrees off, but transfers are hard to measure either way. I'll keep doing it both ways for a while, just to prove the point. The port maps are quicker and you can do it while you have the jug off, so it does have its advantages.

Timberwolf reported 180 degrees duration on a recent 660.

Another AS member PM'd me that his 660 timing numbers were so high, he was reluctant to post the numbers because nobody would believe him.

Don't get me wrong, I love the 066. It's the small block chevy of chainsaws. But just as there are good SBC heads and bad SBC heads, there seem to be good 066 jugs and bad 066 jugs -- and no obvious way to identify which is which.

Except...... it seems like the good jugs usually have a broken fin or two. :D

I gotta go work on my Oly to recharge my enthusiasm. It would be funny if, when it gets done, the 81cc Oly cuts faster than my 066.
 
OK, degree wheel numbers, to make Brad happy. :)

Squish was 0.034" with standard gasket, rather than the 0.025" used in the computer model.

Exhaust duration 168 degrees.

Intake duration 164 degrees

Blowdown 22 degrees

The degree wheel numbers are closer to Brad's broken fin jug. That's not so terrible, but still pretty aggressive.

If I do a pop-up, the intake duration will climb about 4 degrees. Exhaust duration may drop a degree or two after setting squish.
 
mtngun said:
OK, degree wheel numbers, to make Brad happy. :)

Squish was 0.034" with standard gasket, rather than the 0.025" used in the computer model.

Exhaust duration 168 degrees.

Intake duration 164 degrees

Blowdown 22 degrees

The degree wheel numbers are closer to Brad's broken fin jug. That's not so terrible, but still pretty aggressive.

If I do a pop-up, the intake duration will climb about 4 degrees. Exhaust duration may drop a degree or two after setting squish.
Click to expand...

The exhaust at 96° ATDC and transfers 118° is a lot more reasonable.
 
mtngun said:
If you have been following my other 066 threads, you know I ebayed a used 066 jug to replace the other disastrous top ends. A Meteor piston is also on the way.

Looks like Grande Dog will be sending me a 54mm NWP kit, too, to replace the funky BB kit, so that is also a very interesting possibility.

Meanwhile, let's take a look at this used jug and see how bad it is. It appears to be a recent 660 jug, not 066. The bore seems great, no scratches or pits.

Port maps, old OEM on top, new-to-me OEM on bottom. Sorry for the fuzzy pic, but you can still read it. Pretty much the same port timing and shapes, except the newer jug has a shorter exhaust port.
attachment.php


Let's pretend this jug is installed in a stock saw, with the typical 0.025" squish. Here's the resulting port timing, using the calculator at modelenginenews.com.

Exhaust opens: 93.5° ATDC
Exhaust closes: 86.5° ABDC
Exhaust duration: 173.0° :mad:

Transfer opens: 115.0° ATDC
Transfer closes: 65.0° ABDC
Transfer duration: 130.0°

Inlet opens: 100.5° ABDC
Inlet closes: 79.5° ATDC
Inlet duration: 159.0°

Blowdown period: 21.5°

OK, so the port timing is terrible, at least for milling.

The zero-squish chamber volume is 10cc. My old OEM jug was 9.5cc, so the new jug is worse. Insert your favorite swear words here. :censored:

Well, what's a guy going to do (besides switch to a different brand of saw) ?

Buying used 066 jugs is a crap shoot. You might get lucky and get a jug with good timing and compression, or not.

Buying new 660 jugs -- well, I've only heard bad things about the new 660 jugs. Besides, I can't afford a new 660 jug.

Too bad one of the aftermarket makers doesn't step up to the plate with an 066 P&C kit that has sane port timing and a smaller chamber volume, hint, hint. :)

I'll won't do anything with this jug until I have a chance to inspect the NWP. I'll install whichever jug has better specs, but I'm guessing they will be two peas in a pod.
Click to expand...

Why are Stihl's so crazy timing numbers stock?? I see a 395 in your future! Want me to build you one!! LOL
 
stihlboy said:
:hmm3grin2orange: i know im :deadhorse: lol
Click to expand...

TRI955 said:
Looks like your little puppy is following somebody else....funny what a few months can do. :rolleyes:

:cheers:
Mike
Click to expand...

ha ha ha ha.

WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF WOOF
 
Those timing numbers are most likely matched to the restrictive muffler Stihl has to use these days. The long exhaust duration is needed to empty the cylinder through the soda straw outlet. Modding is not taken in to account.


.
 
Received the latest and greatest 066BB kit today from Grande Dog.

I still haven't decided which top end I will install, but here's a quick rundown on the BB specs. Durations based on port map and computer, not degree wheel.

170 degree exhaust duration (assuming 0.020" squish)
175 degree intake duration :confused:
30.5 degree blowdown
8.6 cc zero-squish chamber volume
NO free port :clap:

41.1 mm piston height
23 mm pin-center-to-top-of-piston
3.25 mm (0.130") top land (vs. 0.120" top land on my 2008 vintage BB piston)

The good news is they did NOT raise the roof of the exhaust 2mm as stated in a thread on the Bailey's forum. The floor was raised enough to eliminate the free port problem, but the roof was left alone.

Also they shrank the chamber volume, as expected. :clap:

I didn't have time to take pictures of the port map but here are the critical numbers, measured from the squish band:

25.2 mm to top of exhaust port, port is 16.1 mm high
63.7 mm to bottom of intake port
34.1 mm to top of transfer

So........ progress has been made, but there is still room for improvement. I would prefer to see 150 - 160 degrees duration, and there are still some QC issues which I am discussing in private with Grande Dog.
 
mtngun said:
Received the latest and greatest 066BB kit today from Grande Dog.

I still haven't decided which top end I will install, but here's a quick rundown on the BB specs. Durations based on port map and computer, not degree wheel.

170 degree exhaust duration (assuming 0.020" squish)
175 degree intake duration :confused:
30.5 degree blowdown
8.6 cc zero-squish chamber volume
NO free port :clap:

41.1 mm piston height
23 mm pin-center-to-top-of-piston
3.25 mm (0.130") top land (vs. 0.120" top land on my 2008 vintage BB piston)

The good news is they did NOT raise the roof of the exhaust 2mm as stated in a thread on the Bailey's forum. The floor was raised enough to eliminate the free port problem, but the roof was left alone.

Also they shrank the chamber volume, as expected. :clap:

I didn't have time to take pictures of the port map but here are the critical numbers, measured from the squish band:

25.2 mm to top of exhaust port, port is 16.1 mm high
63.7 mm to bottom of intake port
34.1 mm to top of transfer

So........ progress has been made, but there is still room for improvement. I would prefer to see 150 - 160 degrees duration, and there are still some QC issues which I am discussing in private with Grande Dog.
Click to expand...

Sounds like a step in the right direction. :clap:
 
Does the piston in the new big bore kit leave you enough pistion skirt to turn a pop-up without any freeporting? If yes it looks like that might be the best answer to your quest here for more compression.

Seems like you efforts are finally paying off here a little.




Mr. HE:cool:
 
Wow, all those #'s and figures are way beyond me, but it looks like mountaingun has done his homework and I'd like to see the saw in action.
My findings on the 044 -066 is that Stihl has done a great job on the porting of these saws and all they seem to need is a longer intake duration, larger muff opening and a bit less squish, not to mention a real sharp chain and an aggressive operator who knows how to read the wood.
Regardless, it's all in the name of fun.
Gypo
 
My 066 with this kit ported is the strongest 066 I've run. Don't worry about the seemingly excessive intake duration. It runs great.

Here's where mine sits after porting.

Exhaust - 96 / 168
Transfers - 121 / 118
Intake - 87 / 174
Blowdown - 25
 
Last edited:
Hddnis said:
Does the piston in the new big bore kit leave you enough pistion skirt to turn a pop-up without any freeporting?
Click to expand...
There is enough skirt below the exhaust port to do a mild pop-up, providing the very top of the bore has good plating.

Mr. Snelling said:
Don't worry about the seemingly excessive intake duration. It runs great.
Click to expand...
It probably does run great for crosscutting. But .... have you milled with it yet ?

A milling saw spends its entire life at 8500 - 10,500 rpm. Midrange is what it's all about. Top end means nothing.

My Meteor piston is still backordered. I'm not going to choose a top end until I've had a chance to examine the Meteor and figure out how much pop-up can be safely done with the used OEM jug.
 
mtngun said:
There is enough skirt below the exhaust port to do a mild pop-up, providing the very top of the bore has good plating.

It probably does run great for crosscutting. But .... have you milled with it yet ?

A milling saw spends its entire life at 8500 - 10,500 rpm. Midrange is what it's all about. Top end means nothing.

My Meteor piston is still backordered. I'm not going to choose a top end until I've had a chance to examine the Meteor and figure out how much pop-up can be safely done with the used OEM jug.
Click to expand...

No lack of mid-range here. It's a work saw, not a race saw. I port for torque. I didn't raise the exhaust at all.
 

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