runner port volume / head CC measurements

[Caprimaniac]

Well, hi.

How do vendors measure the CC of their heads- With valves installed?

I was thinking greasing up the seats and stems to seal and pour some kind of Liquid, water I'd think, to measure. Just for comparisson to as cast and see the variance after porting.

[mag2555]

Yes, with the valves in place.

Use rubbing Alcohol to pour in.

The main factor in where a given head will peak rpm wise in power is the heads and or complete Intake systems minimum port area and not the overall port volume!
Two head of the same type and port volume can make there best power due to port area up to 1500 rpm apart from each other.

What you really want to know also is how much flow gain you are picking up per CC of port volume gain .
Your percent of flow gain should equal or exceed your percent of port volume increase, when this stops taking place if your a novist porter , then you had better stop grinding right then and there!

[GARY C]

Yes, with the valves in place.

Use rubbing Alcohol to pour in.

The main factor in where a given head will peak rpm wise in power is the heads and or complete Intake systems minimum port area and not the overall port volume!
Two head of the same type and port volume can make there best power due to port area up to 1500 rpm apart from each other.

What you really want to know also is how much flow gain you are picking up per CC of port volume gain .
Your percent of flow gain should equal or exceed your percent of port volume increase, when this stops taking place if your a novist porter , then you had better stop grinding right then and there!

I wish you had written this years ago when I started playing with port work.

[KnightEngines]

Your percent of flow gain should equal or exceed your percent of port volume increase, when this stops taking place if your a novist porter , then you had better stop grinding right then and there!

Up & coming head porter advice 101. Very well put.

[Caprimaniac]

Great input, thanks.

Indeed, not porting for cc goal. Have figured out CSA, throat area, etc needed vs rpm and cui.

Know cc of heads used in other contexts and wish to compare.
And use as a tool to compare runners, in addition to caliper measurements, to compare runners for consistency berore I snd them out to bench flowing. (And then take back for more work...? - we’ll see)

[mag2555]

If you want a full picture of what going on , then when you send the heads out for flow testing spend the extra money for a added test done with the Intake bolted on.

[Frankshaft]

Your percent of flow gain should equal or exceed your percent of port volume increase, when this stops taking place if your a novist porter , then you had better stop grinding right then and there!

Up & coming head porter advice 101. Very well put.

Not in every case. What if the port is smoking fast and you want to slow it down? Wouldn't then the goal be to increase cross section with minimal flow gains? If the case above happened, wouldn't the port still be smoking fast?

[mag2555]

Quite true, but was referring to the novist who is just grinding and counting up CC's without the aid of a flow bench how are you going to know about have much you have changed the fps with your mod's

[Frankshaft]

Quite true, but was referring to the novist who is just grinding and counting up CC's without the aid of a flow bench how are you going to know about have much you have changed the fps with your mod's

Good point.

[user-29956]

If you want a full picture of what going on , then when you send the heads out for flow testing spend the extra money for a added test done with the Intake bolted on.

True. This could lend some insight into the available "PORT ELASTICITY " on this conduit in particular!

[Frankshaft]

If you want a full picture of what going on , then when you send the heads out for flow testing spend the extra money for a added test done with the Intake bolted on.

True. This could lend some insight into the available "PORT ELASTICITY " on this conduit in particular!

What about the port reflectivity? Anyone ever test that? Once you do, wow, it's like a blind man being able to see for the first time.

[mag2555]

One thing that's amazing and hard to get your head around is that reflectivity is a wave and as such is not limited speed wise like air mass and fuel is traveling up and down the Intake tract!

[user-29956]

One thing that's amazing and hard to get your head around is that reflectivity is a wave and as such is not limited speed wise like air mass and fuel is traveling up and down the Intake tract!

And to a greater extent the elastic modulus of the air column!

...Vincent Dizziano

[mag2555]

I am not sure what you are saying with your "elastic nature " comment, but to me the only way the air colume in a NA motor can be elastic is by means of temperature changes ( as in density) applied during its travel from the inlet of the Carb and into the chamber until light off takes place







" A lie can make its way around the world before the truth can even get it pants on!"
Churchill I think?

[user-29956]

I am not sure what you are saying with your "elastic nature " comment, but to me the only way the air colume in a NA motor can be elastic is by means of temperature changes ( as in density) applied during its travel from the inlet of the Carb and into the chamber until light off takes place
I don't blame you for not understanding, I blame myself for not teaching it correctly......not always my strong point. Perhaps I will open up a thread in the advanced section that may clear some things up when more time is available to me. For now. Try to picture a slingshot released just before the point of breakage! This would be your goal for most VE within any given confine...back to work. Long long days of R+D as of late!

Vincent Dizziano





" A lie can make its way around the world before the truth can even get it pants on!"
Churchill I think?