440 finger ports

[blsnelling]

I don't think the model crowd or the bike crowd bother to debate it. Boost ports are nearly always as standard or added. And a fair few older karts motors had them, if not all.

I believe boost ports on bikes and sleds are typically fed from a different source. These fingers are feeding from the same source as the original transfer port.

Fingers do move flow to the back of the cylinder. However, widened transfers direct their charge to to same area if shaped correctly.

I've admittedly never tried finger ports. This is just my opinion. Honestly, I hate to remove that much cylinder surface in a work saw, the same reason I'm hesitant to use epoxy in a work saw. I've seen it work, but when might it fail. I don't want to go there. Again, just my perspective on it.

In a race saw, additional boost ports are often added, but done so through externally molded ports.

 

[Chainsaw Jim]

In a race saw, additional boost ports are often added, but done so through externally molded ports.

Or by this method...

 

[Iggy]

Thanks guys! i know it's a bit ugly so that's a fair assessment @Deets066, I was working on cleaning them up a bit last night, not going too fast.
When I first started using the grinder i had a hell of a time getting it to not jump when cutting, that's why I started on this jug though. I'm getting better but still in question how you guys get your ports so smooth like @drf256. I'll definitely keep all these tips handy when I'm setting up to do my next jug. How much effect does the placement of your finger port at the lower transfer have on performance?
I had enough room with this piston to spin it around, it's close but I didn't plan on this jug lasting too long anyway so I'm pushing things I usually wouldn't, I'm doing a whole lot of trial and error.

 

[Sawsparky]

I have been reading for a very long time. Built a few saws and am constantly testing/tuning and ruining perfectly good parts. Ehh..... parts are cheap? The idea of flow/velocity/direction/timing/shape/size are all key, obviously. Just when I feel I understand one, another comes into play.

Or by this method...

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Would you care to elaborate on this? Setup? Use? Why? Never seen anything like it in saws yet? I think they have pistons like that in the bike? Kart? game.

 

[MustangMike]

Welcome to our nutty site, hope you enjoy it!

Also, please contribute re: your builds.

 

[Nutball]

With fingers, and possibly bridges too, I'd keep in mind the direction the crank moves. Your boosters are pointing nearly perpendicular to the crank direction. I think boosters that aim upward straighter and are not nearly as directed from the lower transfers would allow for easier flow blown right off the crank.

I probably could have just done a couple big straight fingers, but this is the first cylinder I ever ported.

 

[Chainsaw Jim]

Would you care to elaborate on this? Setup? Use? Why? Never seen anything like it in saws yet? I think they have pistons like that in the bike? Kart? game.

I was just playing around before I really knew what I was doing. That's an 041 super which isn't your typical race saw candidate. Though my opinion may change after I get back into it.

 

[drf256]

Thanks guys! i know it's a bit ugly so that's a fair assessment @Deets066, I was working on cleaning them up a bit last night, not going too fast.
When I first started using the grinder i had a hell of a time getting it to not jump when cutting, that's why I started on this jug though. I'm getting better but still in question how you guys get your ports so smooth like @drf256. I'll definitely keep all these tips handy when I'm setting up to do my next jug. How much effect does the placement of your finger port at the lower transfer have on performance?
I had enough room with this piston to spin it around, it's close but I didn't plan on this jug lasting too long anyway so I'm pushing things I usually wouldn't, I'm doing a whole lot of trial and error.

I use 4 different size ball/sphere carbide burrs.

 

[drf256]

Not that I’m that great at them, but I want to illustrate what I mean. Also, I open the “feed” area from the lower to the finger more than I used to now.

Kinda think of a funnel feeding it.

View attachment 161055 View attachment 161056 View attachment 161057 View attachment 161058

Is that a 262xp cylinder in mixed in there

Yes

@ranchdadmike 262XP

 

[Sawsparky]

Opening the lowers and creating the fingers, making the transfer area much larger. Does one take intake timing into account?

As stated the Intake port width is confined but are these something that you know you want from the start? Would you adjust intake timing accordingly? If exhaust was where you wanted it.

Would timing/area be more important than flow/velocity with fingers?

 

[Iggy]

I

I use 4 different size ball/sphere carbide burrs.

I'll have to try that, I was using longer tapered carbide burrs.

 

[MustangMike]

On a lot of cylinders the intake provides a lot of opportunity to improve performance, but unlike the exhaust, going as wide as is safe is not always prudent.

The shape, width and timing of the intake can make a saw lazy, or a fuel hog. So, if your goal is to build a work saw, I would not go overboard with mods to the intake.

 

[Sawsparky]

My interpretation of that is. With this application, Velocity/flow is more important than duration for a finger ported work saw. Maintain stock port shape and focus on shape/direction of finger???

I’m asking. I know nothing.

Trying to keep it finger related...

 

[Iggy]

In my head with the minimal knowledge that I have with building saws I felt that reducing the size of my lowers would gain me some velocity. I just hope that I still have the right volume and velocity for both to work effectively.
I was shooting for the fuel to come out of the uppers fast enough to quickly lift the exhaust gasses off the top of the piston and without fighting the fresh charge coming out of the fingers. In a perfect world the added velocity from decreasing the size of the lower and making the fingers small would help push the exhaust gas out more effectively, in a straighter path with less turbulence than just bouncing your fresh charge off the intake side of the cylinder.
I'm sure there's other ways to do this but I really wanted to test a theory and try finger ports. I very well could have made it run like crap, only one way to find out though.

 

[Nutball]

Enlarging the lowers increases case volume slowing velocity, but that's probably insignificant compared to smooth easy flow over the corners into the transfers combined with the funneling effect that pulls from a wider area and gradually boosts velocity by the time the gases reach the uppers.

 

[MustangMike]

Run it and see, and we can all learn.

 

[Sawsparky]

Filling the trans was actually something I tried awhile back. Only ran it maybe a tank? I got my trans higher than I thought I needed and really wanted to see if the JB-weld would hold up..... Didn’t notice much of difference? but the JB weld was still there!

Some of the AM junk I used to practice on I still got laying around for some reason.

 

[Bigmac]

Or by this method...

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I have wanted to do that to a 076

 

[Chainsaw Jim]

I have wanted to do that to a 076

I will eventually. Hopefully the wall is thick enough. I'm not sure if it was originally cast from an over-bored 051 cylinder or not.