066 port Timing numbers

[JT78]

Ok so the 066 I am rebuilding had swallowed something at some point and the exhaust port and piston were damaged. I had planned to port this saw as well but had to raise the roof a bit more than I had wanted to. So the final numbers I ended up with are intake,transfers,exhaust 82/118/94
So is this thing gonna run decent?
I did a lot of research looking for port timing numbers and it seems a little high on the exhaust and long on blowdown but everything else should be in check.
Also I am running a Dukes pop up piston so I think compression should be good still ?
Pic is from before I pulled it all apart.

 

[Dolkitafreak]

Compression will be pretty low. I or someone else can machine that cylinder to get the exhaust down-then raise transfers back up to reduce blowdown and likely fill the intake some.

 

[Moparmyway]

One of the best running 066’s I’ve ever seen was 95 / 115 / 79

I say run it and see how she does

 

[Paul Fithian]

My G660 runs great at these numbers
- Exhaust: 97
- Transfer: 117
- Intake: 82

 

[mattr66]

What's your current squish clearance? If you have room for a little cylinder base trim, it will raise compressions in 2 ways by lowering the exhaust port and reducing chamber volume at TDC. If you are 150+ psi when done you should have a decent running saw.

 

[Redfin]

Ok so the 066 I am rebuilding had swallowed something at some point and the exhaust port and piston were damaged. I had planned to port this saw as well but had to raise the roof a bit more than I had wanted to. So the final numbers I ended up with are intake,transfers,exhaust 82/118/94
So is this thing gonna run decent?
I did a lot of research looking for port timing numbers and it seems a little high on the exhaust and long on blowdown but everything else should be in check.
Also I am running a Dukes pop up piston so I think compression should be good still ?
Pic is from before I pulled it all apart. View attachment 367305

How tall a pop up? .030” or close you will be fine with comp. Tad long on bd but Id hazard you will be surprised how that saw runs.

 

[JT78]

Well I got the saw buttoned up, didn't measure the pop up looking at it I'm guessing probably .030 waiting on the new oiler and the saw will be done. I can say I pulled it over a few times and it feels like it has almost as much compression as my clone saw that Shawn Carr built which is around 200 psi if I had to guess. Once the oiler comes in and I get the saw running and throw it in some wood I will post a video here. This isn't my saw by the way it's going to a buddy that owns a tree company he picked it up for 60 bucks at a flea market.

 

[JT78]

Also squish is at .022

 

[Ketchup]

I wouldn’t trust the bearings. Did you change them out?

It might help to keep the muffler outlet on the small side. Can you raise the transfers?

If you did the bearings, there’s no harm in running it.

 

[JT78]

Well I didn't do any video just lazy, but I did run 3 tanks of gas through the saw and it is definitely no slouch. I could tell after the 2nd tank the saw started to pick up quite a bit not as much torque as my other saws but still pulls a 32 buried in oak with authority.

 

[Paul Fithian]

Squish on mine was 0.020”. See https://opeforum.com/threads/holzfforma-g660-ported-cylinder-for-milling.28246/

 

[drf256]

One of the best 066 I’ve ran was @hseII 066 built by Randy Dunlop. He used @mdavlee numbers IIRC and the exhaust was somewhere in the 92-94 range. It pulled a 36” 404 chain with authority and beat up the rest of our saws including a big bore I built with a 395 piston.

I believe the 066 platform is limited by the skirt width on the piston. They need more exhaust duration because of it.

 

[drf256]

The other thing is that you really don’t want a lot of compression on that saw. I’d try a flat top slug and see how it runs.

Believe it or not, raising the exhaust roof doesn’t reduce compression as much as one would think.

I like an 066 with 180-200 psi of compression myself.

 

[srcarr52]

The other thing is that you really don’t want a lot of compression on that saw. I’d try a flat top slug and see how it runs.

Believe it or not, raising the exhaust roof doesn’t reduce compression as much as one would think.

I like an 066 with 180-200 psi of compression myself.

Elasto-start handles are a must!

 

[Funky sawman]

The other thing is that you really don’t want a lot of compression on that saw. I’d try a flat top slug and see how it runs.

Believe it or not, raising the exhaust roof doesn’t reduce compression as much as one would think.

I like an 066 with 180-200 psi of compression myself.

Yea anything more than 200 psi is heck on starter components, even with a good decom. That unmodified cross cylinder is pumping 185 psi with the factory base gasket, at .022" squish. All I know is the numbers in that Cross cylinder are spot on for a everyday work saw

 

[JT78]

Owner hasn't picked it up yet so I got some video today.

 

[Moparmyway]

I’m thinking that’s looking and sounding pretty good