2.055 Speedmaster Porting Progression

[Earlie A]

In simple terms, my take on that is the longer/steeper top cut allowed the numbers to continue to climb, then the SSR took over and with the valve that far from the seat, is back in control.

Totally agree. And although the curve is not as 'pretty', I would argue that the throat is more efficient with the wider top cut. Lowering the apex at this point would pick up the 0.600 and above numbers, but decrease the flow peak at 0.550. I sort of like holding onto the short side as long as possible. Just something else it would be nice to test.

 

[273]

I really like the .300 & .400 numbers, either way that head should produce pretty good power in the right combo.

 

[Earlie A]

I really like the .300 & .400 numbers, either way that head should produce pretty good power in the right combo.

They are decent numbers - until TF comes along.

 

[273]

They are decent numbers - until TF comes along.

True TF are definitely gonna make more power.

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I don't know if the best way, I judge flow curves by, 150 cfm @ .200, 200 cfm @ .300, 250 @ .400, 300 cfm @ .500, 350 cfm @ .600, whatever angle that cfm per lift is, gives me an easy frame of reference.

From the heads I've seem decent ones are around there, obviously there's ones do a lot better or worse but to me seem like if you had a head following around that curve there doing pretty well. Obviously heads of different peak cfm gonna stop at different points of that.

But yes those TF doing decently better at those points.

 

[Earlie A]

I don't know if the best way, I judge flow curves by, 150 cfm @ .200, 200 cfm @ .300, 250 @ .400, 300 cfm @ .500, 350 cfm @ .600, whatever angle that cfm per lift is, gives me an easy frame of reference.

So what you have done in your mind is to create your own flow coefficient or coefficient of discharge. You are comparing what you see to some ‘known’ standard of perfection, and that is valid. Take it a step further and create a coefficient that not only contains cfm and valve lift, but port volume as well. Look at cfm divided by valve lift divided by port volume.

Or, calculate the curtain area for each valve lift and divide the cfm at that lift by the curtain area. That will give you velocity through the curtain area. Then compare the velocities at different lift points. Why are some better than others?

Morgan talks about using all kinds of different flow coefficients to analyze ports. You can create your own and that is exactly what you have done.

 

[Alfajim]

So what you have done in your mind is to create your own flow coefficient or coefficient of discharge. You are comparing what you see to some ‘known’ standard of perfection, and that is valid. Take it a step further and create a coefficient that not only contains cfm and valve lift, but port volume as well. Look at cfm divided by valve lift divided by port volume.

Or, calculate the curtain area for each valve lift and divide the cfm at that lift by the curtain area. That will give you velocity through the curtain area. Then compare the velocities at different lift points. Why are some better than others?

Morgan talks about using all kinds of different flow coefficients to analyze ports. You can create your own and that is exactly what you have done.

Earlie, do you have a velocity probe for you bench? My friend in Salt Lake had a special bench with a velocity probe to see where the port was most efficient and or less so at the lift and flow points. It illustrated some very interesting things going on with the ports and how actually efficient it was.
Back when I was doing the Allison's I sectioned up a cylinder head and built the tools to mount it on the flow bench to see how the ports worked and really interesting results it showed why the turbo Allison's didn't work like it should have. they could never get the engine into positive differential there was always more back pressure the inlet pressure. It was because the exports where so efficient 98% at full lift max flow the intakes where only about 80% because of there particular design, storage pockets on the outer half of the port, Jerry Magnuson said they where prober supercharger ports. It also pointed out that there was way to much camshaft 70* overlap.

 

[Earlie A]

Earlie, do you have a velocity probe for you bench? My friend in Salt Lake had a special bench with a velocity probe to see where the port was most efficient and or less so at the lift and flow points. It illustrated some very interesting things going on with the ports and how actually efficient it was.

Yes Jim, velocity probes are an essential tool on the flowbench. But just like any other tool, they have their limitations. Pitot tube style velocity probes are particularly good when they can be aligned directly into a relatively linear airstream. They will give misleading information when used at an angle to an airstream stream or in a turbulent area.

A short string on a wire is useful in turbulent areas.

 

[Alfajim]

Yes Jim, velocity probes are an essential tool on the flowbench. But just like any other tool, they have their limitations. Pitot tube style velocity probes are particularly good when they can be aligned directly into a relatively linear airstream. They will give misleading information when used at an angle to an airstream stream or in a turbulent area.

A short string on a wire is useful in turbulent areas.

Yes I agree this was back in the mid 70's so flow benches then with a velocity probe where rare his was a pitot tube style. It was very interesting to watch.