#1  
Old 11-27-2021, 01:58 AM
tooski tooski is offline
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Default KRE 290

Quote:
Originally Posted by steve25 View Post
.
The formula for the minimum amount of valve lift is this D/.25.
So for a 2.11” valve to star to well utilize a given port the valve lift needs to be a minimum of .527” .
Then, what HFT cam would you recommend for a 10.15:1 406 with KRE 290's? My lift is just shy of .520 with 1.65 rockers.

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Last edited by tooski; 11-27-2021 at 02:09 AM.
  #2  
Old 11-27-2021, 08:25 AM
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Hi and sorry for the lack of complete info with what I posted, but I had the power go out here and my phone was on the charger and I wanted to save the minimal charge in it that it had.

Let’s talk minimum’s and then maximum’s for a bit in terms of geometry, and then relate that to the size of a given port.

In terms of a any valve size there is a minimum valve bowl throat diameter that should be used to start to make good use flow wise for a given size valve.

In terms of any valve this minimum ID is 85% of the valve size used.

As this relates to a 2.11” valve the minimum ID the valve bowl should be is 1.79”.

Note that in the stock iron D port heads with a 2.11” valve this stock percentage is 75.5% or a very small diameter of 1.60”.

Now you might say, ok so how does that relate to the size of the rest of the port on back towards the intake flange.

Well it’s simple, we take the throat diameter and times that by 3.14, which in terms of a 1.79” throat comes to 5.62”.

This is the minimum circumference that the port should expand out to as the throat diameter we have expands out.

Now as you might guess there are loads of different port shapes this circumference number could be formed into, and for now let’s leave it at some shapes will flow a lot better then others that might get used!

Speaking in terms of maximum geometric sizes for the throat diameter we find a percentage of 91% and some folks will stretch this to 92 % for a maxed out very high rpm race motor.
These percentage numbers are for the use of 45 degree seat angles or steeper!

Note that the maximum percentage found to work the best with a factory 30 degree intake seat angle is 88%.

Now let’s get back to your valve lift question.

The higher the valve lift used the more a port will flow until we are passing the maximum amount of air that the minimum port area will allow to pass.
Also note that in terms of the minimum port area used that this size may not be in the valve bowl , and this can be a design choice because having the maximum port velocity take place at different locations in the intake port will also control weather the port favor’s making better low speed torque, or better high rpm HP numbers.
This is part of how port volume relates to how well a given size port perform’s in the average rpm band of a given CID motor.

Getting back to valve lift used with this previous info, let’s say your pick for a aftermarket head port volume wise is a little too large to make really good torque in terms of your motors cid and the rpm range you want it to run in.

If your only running .490” lift and the head is known to flow 20 cfm more up at .540” lift, then if you implemented such the action of more air moving thru that same minimum port area will pick up velocity which will translate directly into higher torque numbers!

Now what if your already running a amount of lift that has your head maxed out in terms of air flow.
Well if you get the head ported by someone who knows what they are doing they can provide you with a larger percentage of flow gain then the percentage they enlarge the port by.

This too will increase the port velocity and the torque numbers the motor can produce.

Getting back to your motor, if your going to run a hydro roller in a street motor that will occasionally hit the drag strip I would run .a minimum of 550” to .560” lift , but there should be no need to go over .580” for a motor like yours.

This should provide great power and good valve stem and guide life.
If your going to run a flat tappet hydro Cam then I would be looking at a minimum of .500” lift and you could sneak up to .540” lift if you like.

Please always keep in mind that motors do not make HP directly, they make a given amount of torque at a given rpm.
This means that the higher in rpm a given motor makes max torque, then the larger the HP number will be had.

Torque X rpm / by 5252 = HP.

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  #3  
Old 11-27-2021, 08:49 AM
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Also note that besides the max intake flow numbers determine how much hp a motor can make, so does the maximum port velocity serve to limit the amount of hp that is produced.

For example it’s very possible that a head can flow enough that a motor could make 700 hp at 6500 rpm, but if the port velocity exceeds a certain number by let’s say 5500 rpm then it does not matter that as seen on a flow bench that the head flows enough to make 700 hp.
In use on a given cid motor and at a certain rpm only 625 hp may be produced!

I will pass along the info on how to figure this out another time, because as you might expect it’s pretty involved!
Determining this is complicated, but can be done.

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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs!
And he was not talking about 1/8 or 1/4 mile ETs!

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Two dry rotted 14 x 10 Micky Thompson slicks.

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Two pairs of brown leather flip flops, never seen more then 2 mph.

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Old 11-27-2021, 11:03 AM
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Steve,
Nice write up.

Let me just add that throat area is not only a function of its % of valve size but also what diameter the valve stem is.

Valve Lift of .25 * Valve Diameter is where the curtain area is equal to the valve area.

What I also like to calculate is what the valve lift is for the curtain area to be equal to throat area - valve stem area.

Stan

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Old 11-27-2021, 03:24 PM
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Yes Stan thanks for getting my back and noting important factor I omitted maybe due to morning coffee not kicking in yet all the way, lol!

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And he was not talking about 1/8 or 1/4 mile ETs!

1) 1940s 100% silver 4 cup tea server set.

Two dry rotted 14 x 10 Micky Thompson slicks.

1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.

Education is what your left with once you forget things!
  #6  
Old 11-27-2021, 03:35 PM
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Quote:
Originally Posted by tooski View Post
what HFT cam would you recommend for a 10.15:1 406 with KRE 290's? My lift is just shy of .520 with 1.65 rockers.

I'd be looking for something like

Ultradyne Solid Flat lobe
F18
280 @ .020
247 @ .050
159 @ .200
0.3500 lobe

  #7  
Old 11-27-2021, 04:26 PM
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Quote:
Originally Posted by steve25 View Post
Please always keep in mind that motors do not make HP directly, they make a given amount of torque at a given rpm.
This means that the higher in rpm a given motor makes max torque, then the larger the HP number will be had.

Torque X rpm / by 5252 = HP.
Engines DO make power directly. Here's a power equation that does not use torque at all. Power is energy exchange!
https://www.grc.nasa.gov/www/k-12/airplane/ottoa.html

Also Nascar R&D measures HORSEPOWER for every cylinder in their engine from cylinder pressure.
https://www.youtube.com/watch?v=rBZCnG1HwDM


Yes, piston speed (RPM) is a strong factor.

horsepower = (Displacement x RPM X BMEP) / 792000

horsepower = (BMEP * engine total bore area * MPS) / 132000

MPS is mean piston speed.

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Old 11-27-2021, 04:42 PM
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Quote:
Originally Posted by pastry_chef View Post
Engines DO make power directly. Here's a power equation that does not use torque at all. Power is energy exchange!
https://www.grc.nasa.gov/www/k-12/airplane/ottoa.html

Also Nascar R&D measures HORSEPOWER for every cylinder in their engine from cylinder pressure.
https://www.youtube.com/watch?v=rBZCnG1HwDM


Yes, piston speed (RPM) is a strong factor.

horsepower = (Displacement x RPM X BMEP) / 792000

horsepower = (BMEP * engine total bore area * MPS) / 132000

MPS is mean piston speed.
Mike,
When you look at how to calculate BMEP you see it is a function of torque.

BMEP = (Torque * 150.8) / Cubic Inches

Stan

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Old 11-27-2021, 05:09 PM
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Quote:
Originally Posted by Stan Weiss View Post
Mike,
When you look at how to calculate BMEP you see it is a function of torque.

BMEP = (Torque * 150.8) / Cubic Inches

Stan
I see torque as a function of net cylinder pressure. - tfxengine.com

Clint at TFX could clarify,, but reading from his comments they don't first calculate torque to obtain horsepower. He has strongly expressed many times that horsepower is not simply math.

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Old 11-27-2021, 05:26 PM
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How good are our tools and how deep we want to look.

from Clint Gray at TFX

Quote:
by nitro2 » Mon Dec 12, 2011 10:36 pm
Torque is also mathematical, a strain gauge doesn't measure torque, it measures force, well... it doesn't even do that, it measures strain, which is then mathematically calculated to be a force, the force and leverage is then mathematically calculated to be a torque.

Every engineer knows there are 2 ways to figure this sort of thing out, the hard way and the energy method. Power is the rate of change of energy, kinetic in this case. In the case of a vehicle or inertia dyno (free wheeling), power can be calculated without ever figuring out torque, or even knowing if the vehicle is being accelerated by a wheel, a jet engine, or some guy pushing it to the gas station. But with a water brake dyno you're stuck and you need to figure out torque first, before you can figure out power.

Horsepower is not a function of torque. Horsepower is a function of energy and time.
It so happens that with an IC engine and wheeled vehicle, torque is generated in the process, as opposed to thrust. Though at the piston itself, it is thrust.
Torque confuses the hell out of people.... even someone with a PHD who thinks a higher torque but only 200 HP engine would beat a lower engine torque - 500 HP engine car in the 1/4 mile.. with each car geared optimally. Nope! Not even close.


Last edited by pastry_chef; 11-27-2021 at 05:33 PM.
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Old 11-27-2021, 05:30 PM
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Quote:
Originally Posted by pastry_chef View Post
I see torque as a function of net cylinder pressure. - tfxengine.com

Clint at TFX could clarify,, but reading from his comments they don't first calculate torque to obtain horsepower. He has strongly expressed many times that horsepower is not simply math.
The definition of BMEP is: the average (mean) pressure which, IF imposed on the pistons uniformly from the top to the bottom of each power stroke, would produce the measured (brake) power output.

Please note that BMEP is purely theoretical and has NOTHING to do with ACTUAL CYLINDER PRESSURES. It is simply a tool to evaluate the efficiency of a given engine at producing torque from a given displacement.

http://www.epi-eng.com/piston_engine...ance_yardstick.

Stan

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  #12  
Old 11-27-2021, 05:39 PM
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IMEP, PMEP, FMEP, BMEP.. mentioned in the video in great depth.
https://www.youtube.com/watch?v=rBZCnG1HwDM

A great watch, I'd say a must watch.
Maximize the pressure gains, minimize pressure losses.

Net cylinder pressure over the distance of all power strokes.


Last edited by pastry_chef; 11-27-2021 at 05:44 PM.
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