KG441c
Keith
Why not just take as much from the ceiling to start with , leave the intake around 77 and avoid losing torque with longer bars? U will still keep higher rpm in the cut , keep the torque, avoid spit back and use less fuel right?
MillerModSaws plays with 440R/046D Hybrid
- Thread starter MillerModSaws
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cuttinties
ArboristSite Guru
Raising the ceiling will increase duration but it's not going to be a dramatic increase, nor will you hinder the saws ability to trap the incoming charge.
Deets066
Firewood hack
Lots of good info here fellas, I love these threads
KG441c
Keith
Would be interesting to see that piston cut and that saw ran in the same wood!
KG441c
Keith
Yep. To someone like me thats learning porting and to have Randy, Wiggs, Cuttinties, and Brads input all in one thread is a great learning tool! Thank u fellasLots of good info here fellas, I love these threads
My favorite saw right now is a mildly-ported 046 that Randy cut the squish on and is running an 064 piston.
cuttinties
ArboristSite Guru
Any updates on this saw yet?
Did the entire .059 difference get cut from the chamber?. How much compression do you have?.
Seems to me that raising the intake roof doesn’t increase ‘duration’ because of the way we define the term as it applies to the intake port.
We’re only measuring the amount in degrees (as the port opens) that the piston skirt is clear of the port floor, not the open area it sweeps.
The duration number stays the same regardless of the height of the port.
What’s applicable here is the duration number doesn’t take into account the possibility that the piston skirt in some instances can travel past the roof.
It’s saying how long the port is open but not how much time/area it could potentially have by raising the port ceiling to the maximum limits set by both the height of the piston skirt at tdc and the rings at bdc.
Deets066
Firewood hack
Lots of different theory's here about intake, what about transfer height? How does it affect rpm and torque? I know it differs on each saw, should this hybrid have different transfer height than a regular 046, because of the velocity created by the smaller case?
cuttinties
ArboristSite Guru
Completely dependent on transfer design. It's way different conversation when you start talking about transfers. Honestly I don't mind answering questions but this isn't my thread and I think we've taken attention from OP.
Deets066
Firewood hack
I was talking about transfer design of the 046, and the hybrid, I wouldn't think the op would mind hearing different ideas either 
These threads always end up derailed, at least this is constructive derailment...
I typically run 16° of blowdown on a 460. I've run as little as 14° on a hybrid, but usually a little more. Short blowdown is critical to the performance of these saws. You'll also want to advance the ignition around 6°.
I know it's far from apples to apples but...
Extrapolating from conversations regarding the small crankcase volume of the 7900 and longer blowdown... Could the 440/460 hybrid benefit from a bit more, rather than less?
cuttinties
ArboristSite Guru
Dual port piston fed transfers aren't high velocity transfers. Anything specific you're looking to know?I was talking about transfer design of the 046, and the hybrid, I wouldn't think the op would mind hearing different ideas either
In my experience, no. The 7900 is an animal of an entirely different color.
Deets066
Firewood hack
I see lots of people use 118 for transfer height, what makes this such a good number?
That's only a traditional ballpark number. In no way does it apply to every model. For example, some strato saws will go with 10° of blowdown. On the other end of the spectrum, the 7900 needs more like 28°. Trial and error is required with every model to find the sweet spot.
Deets066
Firewood hack
So when you are building a saw, let's say you have it all back together and run it, how would you determine if you needed to go a few degrees more on tranfer or stay where you are at? Would you be able to notice 3 to 4 degrees?
