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You poor bastard.....Meaning only I reallllly pity you.... I thought you were taking April OFF? My hands ache just looking at 9 jugs.....

I'm gonna get to take part of April off. :laugh:

That would be great to see that saw hang with a 262 but I don't see it happening.

Randy,
Need anymore poulan parts yet?

I don't think it will quite do it either. Close I bet.

Ummmmm....................................


Whut about da FW side bearing Randy? Methinks you skipped a step or two and a couple pichurs.........

Lightening......

What?

Yeah, that's how we do it.
 
I'm still trying to wrap my head around this.

So by what I'm seeing and what you're saying here Randy, piston speed is the fastest at mid stroke, then slows from top to bottom. This would make sense, because at TDC, dwell time is present. So zero piston movement despite crank rotation.

So piston speed must be represented as a sine wave.

So in essence, when you lower a jug, even when you cut an equal popup, you're changing the timing of the jug, period. Whenever you move the port away or towards the centerline of the crank, the degrees of rotation that cause a fixed amount of movement will change.

Removing a fixed amount of material, anywhere, is going to affect the timing numbers as it's a non linear relationship.

So in theory, if I cut the jugs that I've already ported with the numbers you've shared, the BD will change even though the ports aren't moved in relation to each other.
 
I'm still trying to wrap my head around this.

So by what I'm seeing and what you're saying here Randy, piston speed is the fastest at mid stroke, then slows from top to bottom. This would make sense, because at TDC, dwell time is present. So zero piston movement despite crank rotation.

So piston speed must be represented as a sine wave.

So in essence, when you lower a jug, even when you cut an equal popup, you're changing the timing of the jug, period. Whenever you move the port away or towards the centerline of the crank, the degrees of rotation that cause a fixed amount of movement will change.

Removing a fixed amount of material, anywhere, is going to affect the timing numbers as it's a non linear relationship.

So in theory, if I cut the jugs that I've already ported with the numbers you've shared, the BD will change even though the ports aren't moved in relation to each other.
Great post!
 
S0 an intake port should be open for the most amount of TIME because of where it's placed in the chamber. Piston speed would be the slowest of all the ports.

Sorry if I'm giving anyone a headache here, but does the top of the transfer port need to be covered by the rings before the intake opens to I sure no intake back through the transfers?

I'm sorry if I'm hijacking this into a porting theory thread. I'm just trying to make it all click.
 
S0 an intake port should be open for the most amount of TIME because of where it's placed in the chamber. Piston speed would be the slowest of all the ports.

Sorry if I'm giving anyone a headache here, but does the top of the transfer port need to be covered by the rings before the intake opens to I sure no intake back through the transfers?

I'm sorry if I'm hijacking this into a porting theory thread. I'm just trying to make it all click.
Piston speed is the same. The only way to change piston speed is by affecting stroke. The length of time in which the port is open is relative to the Dwell time at top dead center. That's affected by the rod length/stroke. But considering that saws are very short stroke I don't believe that the Dwell time isn't affected quite like you're thinking. Going by chordal width and duration the exhaust is usually open longer, and has more time area than the intake.
 
Piston speed is the same. The only way to change piston speed is by affecting stroke. The length of time in which the port is open is relative to the Dwell time at top dead be center. That's affected by the rod length/stroke. But considering that saws are very short stroke I don't believe that the Dwell time isn't affected quite like you're thinking. Going by chordal width and duration the exhaust is usually open longer, and has more time area than the intake.
How could it be the same?

Look at Randy's numbers. How did his intake only move 2.5*, the exhaust 3* and the transfers move 7* if piston speed was constant.

The piston is moving a different distance per degree of crank rotation at different points.
 
How could it be the same?

Look at Randy's numbers. How did his intake only move 2.5*, the exhaust 3* and the transfers move 7* if piston speed was constant.
Unless you change the stroke piston speed is not changed. What you're seeing is affected more by crank angle than piston speed. The longer the stroke the higher the piston speed. This is why Randy's exhaust height guidelines work so well for him. Higher piston speed allows for higher durations. What appears to make the piston slow or dwell isn't slowing the crank down. For the time you're considering the port open the opposite is closed. So the intake isn't open longer than the exhaust. The durations of the transfers are affected because of the fact the location on the cylinder.

Look at the intake or exhaust ports and you'll notice that they reset (repeat their cycle) very much sooner before the transfers. Another thing to remember is that a smaller port is covered faster than a larger port. Which means that the durations will be affected quicker.
 

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