That question is way above my pay grade. I default to others.
I suspect you are correct in that different valve angles are certainly used in different situations, especially racing.
SBM Edelbrock/Speedmaster Head Data
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I suspect you are correct in that different valve angles are certainly used in different situations, especially racing.
LOL! Above mine as well, hence the question!
I suspect it but I don’t know for sure.
But I got a guy! He’s actually said a couple of times he would love to port my Magnum R/T heads. They did pretty good as cast. He loves everything about them & more so since he has ported regular Magnum heads. He took one look into the intake port and gave a low growl “Oh YEA! Oh yea! Ya gotta let me port these babies.” He wants me to try them out on my destroker engine. The 352. FYI - 360 block with a MP 3.45 crank using Bill Richardsons crank spacers for the small journal crank & a 4.03 bore +.018 flat top slug.
Isn't the valves throat optimal ratio kind of standardized to? Kind of leading me to believe what happens at the valve is somewhat independent of the port.
What PBR said.
My understanding from the induction system masters: In general, if the throat is round, the throat diameter is 85%-92% of the valve OD. 85% on the conservative side or for low valve seat angles and 92% being toward the race end of the spectrum with steeper seat angles. 93% is nearly always too large. The throat size, shape and concentricity with the valve stem are variable and tunable.
As far as the port and valve being independent - not really. The most important part of the port is the valve & seats (the venturi area), 1" in front of the valve (to set the air up to enter the venturi) and 1" after the valve (to efficiently get the air out of the venturi).
Corrections to this information are welcome.
This is above my paygrade also, what I meant by seems somewhat independent, if optimal valve job/area is kind of standardized, seems to me it's independent to the port configuration then.
Not saying I'm right, just an observation.
I think I follow the logic. Not pretending I'm right either. It's my understanding that cid, rpm and # of cylinders determine cfm demand and therefore the ideal valve size. The valve size (somewhat) fixes the throat size. Since cfm is already determined, this fixes the ideal port size because of target port velocities. There are equations for all of this.
The real world of bore sizes, combustion chamber shapes, head bolts, water jackets, pushrod locations, hood clearance height and on an on force the valve and port sizes and configurations to be less than ideal, especially in a older street motor.
Some of the newer HiPo stuff and any good race motor - the whole intake system is totally interdependent.
Don’t forget my little valve test (Ferrea and Liberty) the Liberty valve out flowed the Ferrea valve by a lot. If I was into taking measurements like this gentleman I could probably come up with the difference but I’m not into that type of work. I don’t even measure ports as I let my airspeed dictate what I do. That post was pretty recent if you missed it.
The light bulb finally went off for me here. I get what you are saying now.
I did miss it. I'll look. Thanks
Cid x rpm / 3456 = cfm x VE% = actual cfm (displacement over time)
Eg.
318 @ 6113 rpm 90% ve = 506 cfm
360 @ 5400 rpm 90% ve = 506 cfm
440 @ 4418 rpm 90% ve = 506 cfm
Ideal for a highly competitive racing series or Joe Blows average street strip car/weekend burnout machine? I think to many worry about the 1st but are building the 2nd.
Here's some video's and a channel you might like.
Agree
Haven’t watched those before. Thanks.
The cfm formula above calculates the total cfm demand for the entire engine, the flow that the carburetor would see.
In the second video you posted there is another cfm demand calculation. Cfm=(cid x rpm x 0.0009875)/(# of cylinders). That’s the formula that equates to the demand of 1 cylinder on a flow bench at 28”.
For instance, a 360 engine at 6000 rpm would require a port capable of 266 cfm at 28” on the flow bench. Then, if you know the target velocity, the average CSA can be calculated from the cfm.
I’ll be following along but you guys are way over my head. Lol
Yes, (to me I considered it the dynamic/functional displacement of the engine, in that Eg. I view those 3 engines to be dynamically the same size 506 cubic feet per minute.)
Agree
I think PBR answered that simply and best.
Good videos by Eric W. He explains a bunch of stuff.
I myself am NOT a head porter. While I get what is explained to me and have discussions with a head porter (or two) and get what’s being said and explained, I haven’t deep dive into the field. Hanging out with Charlie, he showed me a few things and did some work on a few heads, one port only for me to copy.
Once my garage is up and operating, which isn’t soon enough! LMAO! When ever is something like this done quick enough?
I’ll be setting up a portion in the garage to do minor machine work. Assemble engines, small head work, etc… This is when I’ll start in on head work and porting.
There is a forum Speedtalk where I am at and I read a bunch there. You can find some well known head porters there and pick up from them. But I also find it a little clicky like. They all have their ideas and methods. I don’t think anyone has a head and shoulder way over another.
Really the bottom line no matter what the math says to do is results. The only result worth the salt is actual in car results. Any porter that’s been doing there work for a while will tell you flow benches can be deceiving and/or lie to you.
This is also the reason you have seen me post in a negative manor about calculators and adhering strictly to the math calculations. While math doesn’t lie is everyone favorite thing to say, it’s easy to under perform and possible though hard to out perform a calculator. The calculator is actually incomplete. It’s just the known math.
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I always say one port is easy, but the work starts porting the other 7 to match. That my simple way of saying it. My buddy won’t even port a head without it being cnc’d first. Who’s the smart one him or me. Lol. He’s done porting work longer than me and went to Joe Mondello’s hands one class. When I told him Joe died I think he felt like crying. He had questions he put off asking him. I’ve usually pick up 10-20 on most cnc’d heads I’ve touched minimum. Just remember a cnc program can’t get every port the same (case in point my TrickFlow heads) so you average out a great port with a good port as that’s what the engine does.
I’m know a fella that spent time at Joe Mondellos head porting school and would stay at his house. He is a heck of a head porter. An excellent fella to boot. He and his dad produce winning engine consistently.
I don't believe we can calculate a perfect engine or math should be valued over known results.
But it's also not random why dyno sims kind of work, how we got formulas and rules of thumbs in the first place.
I do see people over value formulas and rule of thumbs Eg. The carb one, cid x rpm / 3456 = cfm, But there is a underlining mathematical symmetry within all these variables and is how I generally, See add process catalogue all this information. It's how I think
I agree with your conclusions that mathematical equations cannot totally define and predict what is happening in an engine.
But what the math does do is to help give a deeper understanding of the cause and effect of anything. If we can write an equation that approximates something we see in nature, we can look at each individual variable in the equation and see how it effects the whole system.
Case in point is the port size. If the energy of the moving air/fuel mixture can be represented by an equation similar to KE=1/2m*v*v, where KE=kinetic energy, m=mass and v=velocity, we can understand that the velocity of the mixture has a much greater effect on the port energy that the mass of the mixture. That's one reason why velocity is so important. It doesn't matter that the equation is 100% correct, because it is not. But the relationship of the variables is pretty accurate.
Here's one I want to know: In the equation for cfm demand where Cfm=(cid x rpm x 0.0009875)/(# of cylinders), we all know what cid, rpm and # of cylinders are. Where does the 0.0009875 come from? If we knew that answer and understood it, another level of understanding would be opened to us.
But what the math does do is to help give a deeper understanding of the cause and effect of anything. If we can write an equation that approximates something we see in nature, we can look at each individual variable in the equation and see how it effects the whole system.
Case in point is the port size. If the energy of the moving air/fuel mixture can be represented by an equation similar to KE=1/2m*v*v, where KE=kinetic energy, m=mass and v=velocity, we can understand that the velocity of the mixture has a much greater effect on the port energy that the mass of the mixture. That's one reason why velocity is so important. It doesn't matter that the equation is 100% correct, because it is not. But the relationship of the variables is pretty accurate.
Here's one I want to know: In the equation for cfm demand where Cfm=(cid x rpm x 0.0009875)/(# of cylinders), we all know what cid, rpm and # of cylinders are. Where does the 0.0009875 come from? If we knew that answer and understood it, another level of understanding would be opened to us.
When you 1st posted it I tried for a few minutes to figure where 0.0009875 comes from, part of of it must convert cubic inch to cubic feet, per revolution (every other stroke) 1 cubic in = .0005787 cubic feet / 2, so 360 x 6000 x .0005787/ 8 /2 = 78 actual cfm vs the 266 cfm of need head flow. That's far as I got, problem with head flow is the depends on a depression, there's not a direct translation between the two. Why the carb formula doesn't work unless the goal is to have 1.5 hg at WOT.
You can have port size set to the exact size needed but if that volume is from the wrong area or shaped wrong you have a bunch of crap on your hands. Only way you can do to learn that is have someone teach you or in my case preform over 1000 flow tests.
Then why do you get behind it so much and defend it so hard?
You swore up and down and fought really hard for what…. Years that an engine that calculates to consume 600 cfm should only use that since a larger carb won’t produce any meaningful amount of extra HP but only give a worse throttle response, lower mileage and a crappier pedal feel on the road?
Dozens here argued against you but you stood proud until engine masters showed you wrong.
The applied science is in the program. What’s to argue about there! LOL!
So the formula over valves carbs?I do see people over value formulas and rule of thumbs Eg. The carb one, cid x rpm / 3456 = cfm, But there is a underlining mathematical symmetry within all these variables and is how I generally, See add process catalogue all this information. It's how I think
Is 1.5hg the optimal goal point? For you personally that is.
I think (dangerous problem there!) there’s more to it than that.
It’s gotta be.
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