MS660 Port Timings

[MG porting]

https://www.ebay.com/itm/J-B-Weld-3...Resistant-Metallic-Paste-/143142755836?_ul=CA

I have no idea if it will work. I’ve never tried using this stuff.

That's ok I'll give it a try and let you know. And thank you.

 

[huskihl]

Ive got some on the way, for research...

Me too.

#MichiganMafiaFugginShitUp

 

[cus_deluxe]

Me too.

#MichiganMafiaFugginShitUp

Just hopin itll fill the holes where i ground through top of ex flange on a couple lol.

 

[Brewz]

Good #s, but 96/97 / 122 / 82 may be about perfect IMO!

Why Mike?

I have found differently.
Those numbers are just heading back in the direction of the rubbish china cylinders.

 

[paragonbuilder]

this bigbore times at 98/122/80, I cant wait to get it running but its gunna have to wait, my builds come second to other peoples builds and they just keep rollin in

Good #s, but 96/97 / 122 / 82 may be about perfect IMO!

Why Mike?

I have found differently.
Those numbers are just heading back in the direction of the rubbish china cylinders.

Hell, those numbers are close enough guys timing the same cylinder could be off that much or more...

Besides, porting styles are different, and many things work for different guys. If we all just copy what’s been done we don’t learn anything anyhow.

I appreciate your testing and sharing Tony

 

[MustangMike]

I could be wrong, but the 660s have longer strokes which seems to change things. My Blue Beast seems to run pretty well and is 97, 123, 83 (Chinese Bottom with 066 cylinder and Meteor piston). It is easy to start, and I can lean on it quite a bit.

I also have an Asian 660 (w/ Cross P+C) that someone else ported, the #s are 100, 120 and 80, and I'm not as impressed with it. I think some of my un ported Cross P+C saws ran just as strong, but most of them did have numerically higher exhaust. Maybe it's the transfers that get slow around 120? I'm not sure.

For an 440 or Hybrid or 460 I would prefer 100-102 / 120-122/ 78. I also put together a 460 (w/o any port work) that was 105/127/75 that ran very strong.

My impression is that the longer stroke saws just don't need as numerically high of a exhaust as the shorter stroke saws to produce real nice torque.

 

[MustangMike]

Agree totally with what Dan just said, let us know how it runs, but if you get a chance with an ugly cylinder, try raising the exhaust and lowering the intake a bit on a 066/660.

 

[AlfA01]

Hell, those numbers are close enough guys timing the same cylinder could be off that much or more...

Besides, porting styles are different, and many things work for different guys. If we all just copy what’s been done we don’t learn anything anyhow.

I appreciate your testing and sharing Tony

Totally agree Dan. I'm porting a 066/660 at the moment and got quite different numbers by eyeballing versus the ring method.

 

[AlfA01]

I'm porting an 066/660 at the moment. I got 99/127/82 with no base gasket on my OEM jug.

I also have a Hyway jug I'll just pull numbers on for the helk of it.

 

[Funky sawman]

Is that a KS jug?

 

[ManiacalMark]

Looks like a regular stihl made jug

 

[Wonkydonkey]

I'm no expert, but would say area is harder to replicate where as time is easier. And mix the two, it’s a bit more of a lottery game. And as others say measuring inaccuracies all play a part or not help at all if you can’t replicate it. So I guess that’s why we all seem to get good and best results from x y z.

I think using clay is a good way for measuring area, but not many peeps seem to do this..

Edit... there are a lot of (a few too many) other variables, exhaust baffle and exhust outlet etc. Unless we were all in the same place and using the same exhust and things, if you see what I mean
Cheers.

 

[mdavlee]

I'm no expert, but would say area is harder to replicate where as time is easier. And mix the two, it’s a bit more of a lottery game. And as others say measuring inaccuracies all play a part or not help at all if you can’t replicate it. So I guess that’s why we all seem to get good and best results from x y z.

I think using clay is a good way for measuring area, but not many peeps seem to do this..

Edit... there are a lot of (a few too many) other variables, exhaust baffle and exhust outlet etc. Unless we were all in the same place and using the same exhust and things, if you see what I mean
Cheers.

I traced mine with a pencil to measure area. If you check a 460, 372, and 7900 for time area you’ll find a huge variance.

 

[Terry Syd]

I traced mine with a pencil to measure area. If you check a 460, 372, and 7900 for time area you’ll find a huge variance.

That could be an interesting concept to discuss by itself. What were the differences in time/area, the RPM of the powerband, sizes of carbs, etc.

Heck, a good database of such information may give some parameters for someone modding a saw. It could save them from making mistakes and making the right decision from the beginning (bigger air filter/carb is what is needed, etc)

 

[mdavlee]

That could be an interesting concept to discuss by itself. What were the differences in time/area, the RPM of the powerband, sizes of carbs, etc.

Heck, a good database of such information may give some parameters for someone modding a saw. It could save them from making mistakes and making the right decision from the beginning (bigger air filter/carb is what is needed, etc)

372 ended up with the most area best I remember. I didn’t take into account the piston blocking any of the lower part of the transfers. Carbs were Zama C3 and walbro HD or WJ series. Rpm range was similar. The 7900 had the most power of course. The 372 was faster than the 460 despite giving up the 5 cc

 

[huskyboy]

The 372 was faster than the 460 despite giving up the 5 cc

Don’t tell Jeff

 

[drf256]

My impression is that the longer stroke saws just don't need as numerically high of a exhaust as the shorter stroke saws to produce real nice torque.

You’re not wrong.

A longer stroked saw has a longer distance from a 100* ex roof to the squish band than a shorter stroke saw. It’s part of the reason we time larger displacement saws differently than smaller. You’ll Get much more swept volume in the longer stroked saw at the same degree of ex roof.

The piston has more movement for every degree of crank rotation, and the most movement in the center of the stroke per degree. The most movement per degree will be at and around 90*. Hmmm..., which port measure is closest to that?

Remember, piston speed and movement through a bore per degree is sinusoidal, it’s not linear.