600 HP 350 SBC?

[RevTheory]

gm, that sounds interesting.

Yeah, the solder trick sounds like it'll work. Find the length and enter it here https://www.omnicalculator.com/math/circumference

Shawn,

That calculator only works for a circle. The following from Gary's heads

► 1.85 * 1.194 = 2.2089 sq inches area

► (1.85 * 2) + (1.194 * 2) = 6.088 length

The 2.2089 sq in area produces a circumference of 5.26857

Stan

I thought the idea was to lay solder around the pinch area because the whole thing was hand-formed. Measure the length of your solder and get an area calculation. Did I miss the boat again?

[adam728]

I thought the idea was to lay solder around the pinch area because the whole thing was hand-formed. Measure the length of your solder and get an area calculation. Did I miss the boat again?

Yup. Only gives you the area if it's a perfect circle. Other shapes have less area for a given perimeter.

Look at it this way, a 1 inch wide, 2 in tall rectangular port has an area of 2 square inches, and a perimeter of 6 inches. Mistakenly calculating it as a circle using the perimeter gives 2.87 square inches. Picture something like a clover shape and how little area and how much perimeter it can have.

[GARY C]

All classes allow the Dart to replace the 041 type head. World Products has a legal head as well. The aluminum is certain classes, then of those, certain classes can run angle plug. No matter what, they get hit with added weight to run an aftermarket legal head. Most of the OEM port volumes have to be 164cc whereas the aftermarket stuff is 172cc. Clear as mud!

I am guessing the air speed is sky high on those?

265cfm x 2.4 = 636 / 1.85in² = 344 fps calculated. But measured it's around 360-370 through the pinch

5.300 x 16.387 = 86.9 / 172cc = 1.97 AVG CSA

265cfm x 2.4 = 636 / 1.97 AVG CSA = 323 AVG FPS

If the math is wrong in the first equation wouldn't it be wrong in the last one as well? Makes me wonder why no one has ever adjusted it to fit real world measurements...

[Stan Weiss]

I am guessing the air speed is sky high on those?

265cfm x 2.4 = 636 / 1.85in² = 344 fps calculated. But measured it's around 360-370 through the pinch

5.300 x 16.387 = 86.9 / 172cc = 1.97 AVG CSA

265cfm x 2.4 = 636 / 1.97 AVG CSA = 323 AVG FPS

If the math is wrong in the first equation wouldn't it be wrong in the last one as well? Makes me wonder why no one has ever adjusted it to fit real world measurements...

Gary,
Unless I misunderstand what was posted why is the math wrong? Using 365 fps @ the pinch I get 1.7425 sq in CSA

Stan

[GARY C]

265cfm x 2.4 = 636 / 1.85in² = 344 fps calculated. But measured it's around 360-370 through the pinch

5.300 x 16.387 = 86.9 / 172cc = 1.97 AVG CSA

265cfm x 2.4 = 636 / 1.97 AVG CSA = 323 AVG FPS

If the math is wrong in the first equation wouldn't it be wrong in the last one as well? Makes me wonder why no one has ever adjusted it to fit real world measurements...

Gary,
Unless I misunderstand what was posted why is the math wrong? Using 365 fps @ the pinch I get 1.7425 sq in CSA

Stan... 265cfm x 2.4 = 636 / 1.85in² = 344 fps calculated.

[digger]

Gary, the maths is correct but it's an average that tells you what it would be if you sample at infinite points for the calculation at the section. the more complicated the shape the more points you need to measure if you are trying to measure the average and arrive at same as calaulated as some areas will be faster and others slower.

[GARY C]

Gary, the maths is correct but it's an average that tells you what it would be if you sample at infinite points for the calculation at the section. the more complicated the shape the more points you need to measure if you are trying to measure the average and arrive at same as calaulated as some areas will be faster and others slower.

Correct? based on what?... An average of what? A constant of 2.4?...If what is calculated using 2.4 does not agree with what is measured in real time, how is that correct?

Is it my comment you or Stan should be questioning? or is it 2.4?

265cfm x 2.4 = 636 / 1.85in² = 344 fps ("calculated"). But ("measured") it's around 360-370 through the pinch

5.300 x 16.387 = 86.9 / 172cc = 1.97 AVG CSA

265cfm x 2.4 = 636 / 1.97 AVG CSA = 323 AVG FPS

[digger]

Gary, the maths is correct but it's an average that tells you what it would be if you sample at infinite points for the calculation at the section. the more complicated the shape the more points you need to measure if you are trying to measure the average and arrive at same as calaulated as some areas will be faster and others slower.

Correct? based on what?... An average of what? A constant of 2.4?...If what is calculated using 2.4 does not agree with what is measured in real time, how is that correct?

Is it my comment you or Stan should be questioning? or is it 2.4?

265cfm x 2.4 = 636 / 1.85in² = 344 fps ("calculated"). But ("measured") it's around 360-370 through the pinch

5.300 x 16.387 = 86.9 / 172cc = 1.97 AVG CSA

265cfm x 2.4 = 636 / 1.97 AVG CSA = 323 AVG FPS

first you must understand some defintions:

volumetric flow rate = velocity x area

lets use proper consistent units
CFS = ft/s x ft^2
CIS = in/s x in^2

note that flow bench volumertic flow rate is CFM i.e. per minute not second hence ive used CFS
also note the area is normally stated in^2 not ft^2

rearrange include unit conversion 60sec per min and 12 inch per ft

velocity (ft/s) = volumetric flow (CFM) / Area (in^2) x 12 x 12 / 60
velocity (ft/s) = volumetric flow (CFM) / Area (in^2) / 2.4

the 2.4 is just units conversion (144/60)

the average assumes the velocity profile is equal at every part of the cross sectional slice (which it isnt). so the calculation is a correct for the average. when you probe a port it is not telling the average. its value at a point. if you dont sample "correctly" the answer is incorrect assuming you are trying to measure the average. with some shapes the CSA definition is not clear or logical as flows are compflex not nice like a long unoform pipe so sometimes the theory is misapplied in that the average is not appropriate/sensible to use

[GARY C]

Gary, the maths is correct but it's an average that tells you what it would be if you sample at infinite points for the calculation at the section. the more complicated the shape the more points you need to measure if you are trying to measure the average and arrive at same as calaulated as some areas will be faster and others slower.

Correct? based on what?... An average of what? A constant of 2.4?...If what is calculated using 2.4 does not agree with what is measured in real time, how is that correct?

Is it my comment you or Stan should be questioning? or is it 2.4?

265cfm x 2.4 = 636 / 1.85in² = 344 fps ("calculated"). But ("measured") it's around 360-370 through the pinch

5.300 x 16.387 = 86.9 / 172cc = 1.97 AVG CSA

265cfm x 2.4 = 636 / 1.97 AVG CSA = 323 AVG FPS

first you must understand some defintions:

volumetric flow rate = velocity x area

lets use proper consistent units
CFS = ft/s x ft^2
CIS = in/s x in^2

note that flow bench volumertic flow rate is CFM i.e. per minute not second hence ive used CFS
also note the area is normally stated in^2 not ft^2

rearrange include unit conversion 60sec per min and 12 inch per ft

velocity (ft/s) = volumetric flow (CFM) / Area (in^2) x 12 x 12 / 60
velocity (ft/s) = volumetric flow (CFM) / Area (in^2) / 2.4

the 2.4 is just units conversion (144/60)

the average assumes the velocity profile is equal at every part of the cross sectional slice (which it isnt)

So then you can tell me what I need for the head I have posted here?

[digger]

Correct? based on what?... An average of what? A constant of 2.4?...If what is calculated using 2.4 does not agree with what is measured in real time, how is that correct?

Is it my comment you or Stan should be questioning? or is it 2.4?

first you must understand some defintions:

volumetric flow rate = velocity x area

lets use proper consistent units
CFS = ft/s x ft^2
CIS = in/s x in^2

note that flow bench volumertic flow rate is CFM i.e. per minute not second hence ive used CFS
also note the area is normally stated in^2 not ft^2

rearrange include unit conversion 60sec per min and 12 inch per ft

velocity (ft/s) = volumetric flow (CFM) / Area (in^2) x 12 x 12 / 60
velocity (ft/s) = volumetric flow (CFM) / Area (in^2) / 2.4

the 2.4 is just units conversion (144/60)

the average assumes the velocity profile is equal at every part of the cross sectional slice (which it isnt)

So then you can tell me what I need for the head I have posted here?

what do you need? i dont understand the question

[GARY C]

first you must understand some defintions:

volumetric flow rate = velocity x area

lets use proper consistent units
CFS = ft/s x ft^2
CIS = in/s x in^2

note that flow bench volumertic flow rate is CFM i.e. per minute not second hence ive used CFS
also note the area is normally stated in^2 not ft^2

rearrange include unit conversion 60sec per min and 12 inch per ft

velocity (ft/s) = volumetric flow (CFM) / Area (in^2) x 12 x 12 / 60
velocity (ft/s) = volumetric flow (CFM) / Area (in^2) / 2.4

the 2.4 is just units conversion (144/60)

the average assumes the velocity profile is equal at every part of the cross sectional slice (which it isnt)

So then you can tell me what I need for the head I have posted here?

what do you need? i dont understand the question

Then why are you posting on a thread you don't understand? My head info starts 3 pages back.

[digger]

So then you can tell me what I need for the head I have posted here?

what do you need? i dont understand the question

Then why are you posting on a thread you don't understand? My head info starts 3 pages back.

you asked if the maths was wrong. i simply explained why it isnt. thats why it hasnt been corrected

[GARY C]

what do you need? i dont understand the question

Then why are you posting on a thread you don't understand? My head info starts 3 pages back.

you asked if the maths was wrong. i simply explained why it isnt. thats why it hasnt been corrected

But the person presenting it says it is... So why not address him?

[digger]

Then why are you posting on a thread you don't understand? My head info starts 3 pages back.

you asked if the maths was wrong. i simply explained why it isnt. thats why it hasnt been corrected

But the person presenting it says it is... So why not address him?

He did not use the word wrong at all in the quoted post. I'm guessing he already knows why there is a difference

[Stan Weiss]

Gary,
You know measured the CFM it is constant for that lift. But the port is not a uniform shape / CSA. AS the port CSA varies so does the velocity.

Stan

ab-csa-383-6400.gif