Free Porting issue. *forehead slap*

[kjmatson]

I now understand the big bore kit issue with freeporting. I purchased one for my holtzforma 660 because it is strictly a milling saw. I feel alot better blowing up this saw milling than an oem one. Ive done alot of reading on freeporting and haved herd mixed opinions on it. I have fallen into the opinion of I really don't like the idea of anything getting sucked back into the crankcase if it isn't filtered. Im toying with the idea of building up the exhaust floor to fix the issue. Has anyone here successfully done this considering heat. I've opened the muffler and had a friend make me a sweet cover which helps relieve ALOT of heat problems.

The difference in piston height is .070 being oem is that much longer than the big bore. This difference caused a gap in the exhaust floor at TDC of .0015. I fixed the issue by adding the base gasket back giving me a squish of .043 but id like to get back to the .020 squish i had with the delete. Is the difference in squish that much noticeable I should build up the exhaust floor, or should i just leave well enough alone.

 

[cuinrearview]

Personally I'd throw the gasket back in and chalk it up as a cheap lesson in China crap.

 

[Deets066]

Like you said, it’s a holtzachinka. Run it
I’d leave the gasket out too

 

[kjmatson]

gasket is in there ill just leave it. i bought it as the kit on black friday for $129.00 so i could retire my 066 flat top and beat the crap out of the china saw instead.

 

[kjmatson]

Sweet muffler cover though lol she wakes the valley up

 

[Redfin]

Personally I'd throw the gasket back in and chalk it up as a cheap lesson in China crap.

Like you said, it’s a holtzachinka. Run it
I’d leave the gasket out too

Ah an impasse. What to do?

 

[Maintenance Chief]

Pop up piston ? Maybe rivet a thin piece of steel to the exhaust port floor?

 

[kjmatson]

Pop up piston ? Maybe rivet a thin piece of steel to the exhaust port floor?

Flat piston. It cuts good so I'll just leave it. Cut some cherry today with no problem

 

[Maintenance Chief]

Flat piston. It cuts good so I'll just leave it. Cut some cherry today with no problem

I was seeing that they make a pop up piston for the 56mm bore, but hey if its cutting good never mind. Running video would be great.

 

[kjmatson]

I was seeing that they make a pop up piston for the 56mm bore, but hey if its cutting good never mind. Running video would be great.

Friend of mine got the pop-up piston for his. I have Wednesday and Thursday off so I'll get a video of it running. I have some maple to buck up for firewood. So far very happy with it. I put a tillotson carb and hyway big bore on it. It's going to replace my 066 for milling so it's going to work. See what happens.

 

[Lightning Performance]

Ah an impasse. What to do?

JB Weld

 

[Deets066]

JB Weld

 

[Redfin]

JB Weld

You spelled run it wrong.

 

[MustangMike]

Glad to hear that it is running well, but if you want to change things I would go back to the original cylinder, add a Meteor piston (they include Caber rings) and port the cylinder.

I'll bet it would run stronger and more efficiently. These things really like to drink when you mill with them.

 

[MustangMike]

Hey, I have relatives in West Winfield, which looks like it is fairly close to you.

Some in the town and some a little down on Rte 51.

 

[drf256]

Freeporting won’t hurt nuthin’. Ain’t like it’s a rare OEM piece you are trying to extract max power from.

I bet a used OEM Cylinder will run better, but I built a 56mm big bore that ran pretty well.

I just wouldn’t expect more than $129 worth of longevity from it, it’s Chiwanese after all. You may get lucky.

The theory on freeporting helping performance is that there isn’t much case vacuum left as one approaches TDC, and the flow in the exhaust port may add some Venturi effect into the port, creating a bit more negative pressure to fill case.

 

[kjmatson]

Hey, I have relatives in West Winfield, which looks like it is fairly close to you.

Some in the town and some a little down on Rte 51.

Not far at all. I work closer to there

 

[kjmatson]

Freeporting won’t hurt nuthin’. Ain’t like it’s a rare OEM piece you are trying to extract max power from.

I bet a used OEM Cylinder will run better, but I built a 56mm big bore that ran pretty well.

I just wouldn’t expect more than $129 worth of longevity from it, it’s Chiwanese after all. You may get lucky.

The theory on freeporting helping performance is that there isn’t much case vacuum left as one approaches TDC, and the flow in the exhaust port may add some Venturi effect into the port, creating a bit more negative pressure to fill case.

I'm not expecting much longevity out of it but ya never know. I'm saving up for a 3120xp which will be my milling saw.

Interesting. I read some about freeporting but your explanation makes more sense to me. Thank you.

 

[Mastermind]

The absolute strongest running 660 I ever built was freeporting under the piston about .030".

 

[kjmatson]

As soon as I finish up the other projects I have going on I'm going to pull the jug and get the numbers. Doing a 371xp right now I'm pretty excited about, a 55 and another 036.