5.0 LS cam for 7500.

[In-Tech]

For my application, my initial ~.050" thoughts are:
IVO 30 EVC 23
IVC 68 EVO 61

Should peak around 8600 and peak tq ~5800-6000rpm

I wish I had some more rocker ratio and less rod/stroke ratio but dudes had already bought stuff

Budget limited so probably some LS7/LS3 variant heads. CID Intake manifold, thanks Jon Schmidt(sp?). https://www.cidheads.com/products/cid-l ... e-manifold

I'll probably end up with 3-5 different cams till I'm happy on the dyno. I'll probably try to kill the low lift flow on the intake port after some initial testing but will test both ways...plus some header mods during testing. We'll see

I won't know till testing with this short stroke and horrible rod/stroke ratio. I will test all variants with this combination. The extremely long carry during overlap will tell the tale and I will expose whatever it teaches me

[GARY C]

Can someone else do the calculations using Ben's method?

Using Ben's method I get 197.25 degrees @ 0.050" Now to fair this method uses a fixed VE% of 100%.

Stan

It seems like this type of method would require you to average the flow from all lift points minus the points of reversion and then probably make an entirely new math equation.

[Tom68]

It seems like this type of method would require you to average the flow from all lift points minus the points of reversion and then probably make an entirely new math equation.

Plus the 3456 equation for processed air through a complete engine doesn't use (nor need to use) a vacuum drop, the flow bench does, they're to different measurements that aren't related by number of cylinders or cam timing. You can turn the engine over with an electric motor and physically get the 3456 figure.

Ones sucking air through a port, the other is physical consumption. We know each port processed 1/8 of the 662 cfm per cycle, 83 CFM. To pass that amount of air at 7500 and produce power it had everything that makes the engine make power involved, runner length, af ratio, ignition timing, fuel quality, valve event, overlap etc etc.

The 28" of vacuum airflow is almost empirical data, we know about what we need for x amount of horsepower on X combination because it's all been done before.
So if you make a formula from it for valve open timing or anything else, it will most likely be based on empirical data like the 128 rule, make a formula, throw in the magic factor that makes it come to an answer that you know it will on the dyno.
Bens formula needs a magic correction factor.

[Tom68]

If you measure the curtain area at every .050" of valve lift, you will see why a 2-Valve engine needs much more duration then a 4-valve.

Yer, between the Coyote and the LS we're talking something like 238mm of valve circumference versus 160 odd mm.

F220812367.jpg

cathedral_port_set_1.jpg

[HQM383]

Is the fundamental flaw in his calculation (formula) that if the cylinder head flow test depression is changed from 28” in/h2o then it’s selecting a different cam in search of the same outcome? The other obvious flaw is the head doesn’t present maximum tested flow to the cylinder for all of the cams opening duration so I see what Gary C says about the need for averaging flow at lift points minus reversion degrees which is only known with valve events.

[Tom68]

Is the fundamental flaw in his calculation (formula) that if the cylinder head flow test depression is changed from 28” in/h2o then it’s selecting a different cam in search of the same outcome?

Peak port flow at any depression can't work as a formula for figuring peak HP at revs duration requirement without all the other factors, valve size, port size, runner length, exhaust system etc.
Runner length would be one of the few things that is somewhat constant for peaking power at X revs and it's still not truly constant for different engines.

The other obvious flaw is the head doesn’t present maximum tested flow to the cylinder for all of the cams opening duration so I see what Gary C says about the need for averaging flow at lift points minus reversion degrees which is only known with valve events.

That's where the difference will be between the 4v and 2v duration requirements, 238mm circ will let a lot more air in than 160mm circ at 100 thou lift.
Shouldn't be a lot of reversion at 7500, especially for the 4v that will have way way less overlap and also an earlier inlet valve closing to pass the same amount of air even though both heads may show a peak flow of about 300CFM at 28" on a flow bench.

[HQM383]

Is the fundamental flaw in his calculation (formula) that if the cylinder head flow test depression is changed from 28” in/h2o then it’s selecting a different cam in search of the same outcome?

Peak port flow at any depression can't work as a formula for figuring peak HP at revs duration requirement without all the other factors, valve size, port size, runner length, exhaust system etc.
Runner length would be one of the few things that is somewhat constant for peaking power at X revs and it's still not truly constant for different engines.

That’s right, too many other factors. The way I see it using the data from a developmental tool (flowbench) and including it in the formula the way he has can only spit out erroneous results. It’s been said a million times that an engine doesn’t operate on 28” depression.

[Tom68]

It’s been said a million times that an engine doesn’t operate on 28” depression.

But it can of course be used very accurately to help optimise any given package combined with a power test to confirm the improvements.

Better calculate that 82cfm for the LS as an average flow number.

[Tom68]

Let me try this.

5 l @ 7500 rpm, 662cfm divided by 8 cylinders, 83CFM.

Out of each 720 degrees the intake is drawing for say 240 degrees. So 1/3 of every two revolutions, or 1/6 of a single revolution.

83 CFM divided by 0.16666 equals an average of 498 CFM airflow speed (speed, not quantity of) through the port per intake stroke.

Now we just have to crank up a flow bench to flow 498 CFM at say 400 thou lift and lock the depression rate in.
Any improvements we make there (doesn't allow for wet flow problems) should show as an almost directly proportional power improvement at 7500 for a 305.

400 thou because that will be closer to high piston speed, 300 thou would be closer to average lift but the piston speed will be down, especially on the closing ramp.

[289nate]

Interesting. I did a budget 297 SBF build with about 9.9:1 compression and a cam with an intake lobe of 224 duration at .050 and over .630 lift at the valve with 1.7 rockers. Stock Canfield 195 cylinder head (little over 270 cfm when I had them put on a local flowbench) Parker Funnel Web intake and 750 Holley HP on the dyno. Peak HP was 6,900 rpm. Didn’t like being pulled to 7,500.

Intake valve is moved to the center of the bore on those heads to avoid shrouding and I was trying to get away with roller rockers and a Jomar girdle. After the dyno sessions I could not get over the slight angle the rockers came onto the valve with and how it went to crap pulling to 7,500. Bought the right shaft rockers and it pulled clean to 7,500 at the track. So peak with shaft rockers may have been slightly higher. But never put it back on the dyno. Only track.

New combo will be a 306 cube SBF 11.4:1 compression. This time an overkill AFR 220 cylinder head. Undecided on the single plane intake and will use an old 950 Holley HP. Keeping it under 8,500 rpm for a drag racing application that will get putted around on the street for fun. Stick shift, light car, and short 26” tire. Zero care nor need for low rpm anything. 4-2-1 headers from Calvin Elston (great person to do business with). Cam and valvetrain from Ed Curtis (EDC on this forum and another good person to do business with).

This time the cam is just over 250 at .050 on the intake lobe with over .730 lift. Projected peak is around 7,800. Should be coming together and get on the engine dyno in a couple months. I’ll report results here when it does. These days everything takes longer to get in your hands. Lack of intake manifold options has been KILLING me!

Comparing my new build to a Coyote isn’t something I’ve thought about. But the Coyote will KILL my engine in the lower rpm range even if I do keep up in the mid to high range. But I have my Duramax if I need lowend torque.

[Stan Weiss]

Let me try this.

5 l @ 7500 rpm, 662cfm divided by 8 cylinders, 83CFM.

Out of each 720 degrees the intake is drawing for say 240 degrees. So 1/3 of every two revolutions, or 1/6 of a single revolution.

83 CFM divided by 0.16666 equals an average of 498 CFM airflow speed (speed, not quantity of) through the port per intake stroke.

Now we just have to crank up a flow bench to flow 498 CFM at say 400 thou lift and lock the depression rate in.
Any improvements we make there (doesn't allow for wet flow problems) should show as an almost directly proportional power improvement at 7500 for a 305.

400 thou because that will be closer to high piston speed, 300 thou would be closer to average lift but the piston speed will be down, especially on the closing ramp.

Sorry but I don't agree with your math.

662 / 4 = 165.5 cfm

240 is 2/3 of a single revolution

165.5 / (2 / 3) = 248.25 cfm

Stan

[Tom68]

Let me try this.

5 l @ 7500 rpm, 662cfm divided by 8 cylinders, 83CFM.

Out of each 720 degrees the intake is drawing for say 240 degrees. So 1/3 of every two revolutions, or 1/6 of a single revolution.

83 CFM divided by 0.16666 equals an average of 498 CFM airflow speed (speed, not quantity of) through the port per intake stroke.

Now we just have to crank up a flow bench to flow 498 CFM at say 400 thou lift and lock the depression rate in.
Any improvements we make there (doesn't allow for wet flow problems) should show as an almost directly proportional power improvement at 7500 for a 305.

400 thou because that will be closer to high piston speed, 300 thou would be closer to average lift but the piston speed will be down, especially on the closing ramp.

Sorry but I don't agree with your math.

662 / 4 = 165.5 cfm

240 is 2/3 of a single revolution

165.5 / (2 / 3) = 248.25 cfm

Stan

Yep I see what I messed up. I did say try... Cheers.

248 average for 240 degrees it is.

That's where the 28" makes a nice number for flowing heads.

[289nate]

My brother graduated with honors from cal tech on an internship from JPL. Helped write the landing program on the mars rover. Graduated at the top of his class with honors. You can believe in math or understand you don’t have the information to compute anything beyond a generalization.

[289nate]

Some worship calculations and others worship acceleration down the track. You don’t have to perfectly understand it to realize what works. Just me.

[In-Tech]

Hiya Nate,
Oh we could all brag, lol. The sim in my head says mine will make 589hp. That isn't enough I want 650hp. Maybe with some good trickery on the pipes and some variable valve timing, I'll get what I want