Did any of you horsepower calculator guys ever use this

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Probably true race guys are usually shotting for a certain et time and or it's a continuous progress, street guys when building an engine are really not shooting for any performance goal so it becomes I want 400, 500, 600 hp etc... whatever they think will satisfy them usually eyes bigger than belly syndrome. I think anyone building a car should shoot for a certain et goal even if it's never gonna be raced gives your project focus and everyone wants a certain performance ability even if it's like I'm ok with 16, 15, 14 second et gives you some foundation of what parts to use that will work well together.

As for the HP calculator, I just use the 1.4 cfm per hp rule of thumb and the cid x rpm/3456 = cfm, to get ballpark. So if I wanted a 400 hp engine that peaks around 5000 rpm would be 400 x 1.4 = 560 cfm so 560 x 3456 / 5000 = 387 cid.
It’s all good, just an observation I never gave much thought to until this thread. Lot of car guys at my work for example ask me how much horsepower my engine has, none of them run at the strip though, but I only have a ballpark that I’ll throw out, they seem impressed I guess? But when I’m at the track all I ever get after runs is “what do you got in that thing” or similar but never, ever have I had someone at the track ask how much horsepower. I’ve never overheard anyone ask another person that. ET and mph do the talking.
 
It shows 618hp for the 572.......made 716.

What’s the actual CR for that 589?

10:1 static, 4.565x4.500, 78cc head, 7.1 rod, .130 dish piston, .006 down from what I remember, not sure of the IVC on Herbert roller cam, so guessed@69, so not real good info. I've just recalculated dynamic on wallace and its come out at 7.74 which then came out via that link to 617hp@5057rpm...according to the dyno it made 673@5100 with his 950HP.
 
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The Herbert cam is 262@.050 on the intake, with a 112lsa?

If that’s correct, Relative to what the calculator at the beginning of this thread is asking for, if the cam was in at 108, the closing point at .050 would be 59abdc.

Plugging the numbers into this calculator for a 10:1 589, with a 262@.050 cam in at 108, with the static CR showing 10.01:1, the dynamic CR came out to 7.42.
Hp shows 616@5052rpm.
So, 78hp low.
 
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The Herbert cam is 262@.050 on the intake, with a 112lsa?

If that’s correct, Relative to what the calculator at the beginning of this thread is asking for, if the cam was in at 108, the closing point at .050 would be 59abdc.

Plugging the numbers into this calculator for a 10:1 589, with a 262@.050 cam in at 108, with the static CR showing 10.01:1, the dynamic CR came out to 7.42.
Hp shows 616@5052rpm.
So, 78hp low.

Ok so I'll just keep on using wallace for hp (corrected) and the slide rule for you which is also a bit less, and that software we can forget I think.
 
The Herbert cam is 262@.050 on the intake, with a 112lsa?

If that’s correct, Relative to what the calculator at the beginning of this thread is asking for, if the cam was in at 108, the closing point at .050 would be 59abdc.

Plugging the numbers into this calculator for a 10:1 589, with a 262@.050 cam in at 108, with the static CR showing 10.01:1, the dynamic CR came out to 7.42.
Hp shows 616@5052rpm.
So, 78hp low.

That calculator outcome equals the rule of thumb of 1.4 cfm per hp
 
For every hp you need 1.4cfm?

1.4cfm relative to what?

At what depression?

Total air flow through the motor?

Per cylinder?

Per 8 cylinders?

I’m not seeing how that fits in with my dyno data.
 
For every hp you need 1.4cfm?

1.4cfm relative to what?

At what depression?

Total air flow through the motor?

Per cylinder?

Per 8 cylinders?

I’m not seeing how that fits in with my dyno data.


It's just one of those rule of thumb like 2 hp per head cfm,
So take that 616 hp the other formula came out with and times it by 1.4 cfm
1.4 cfm x 616 hp = 862 cfm
use the formula peeps uses for carb selection but shouldn't cid x rpm / 3456 = cfm
So 862 cfm x 3456 / 589 cid = 5057 rpm

Gives the same basic answer at least on this one, formula is probably based on the 1.4 cfm per hp, quicker to use 1.4 rule of thumb especially if you good a guesstimating peak hp rpm. No formula is gonna be accurate a high percentage of the time ballpark is best we got.
 
For every hp you need 1.4cfm?

1.4cfm relative to what?

At what depression?

Total air flow through the motor?

Per cylinder?

Per 8 cylinders?

I’m not seeing how that fits in with my dyno data.


The 1.4 rule of thumb says your 694 hp 589 cid it should peak hp at 5700 rpm is that close ?
 
you’ve totally lost me.

1.4cfm...... of what?
Carb flow? Head flow?
Does the number of cylinders come into play?

So take that 616 hp the other formula came out with and times it by 1.4 cfm
1.4 cfm x 616 hp = 862 cfm

The thing is..... on the actual dyno, the motor didn’t make 616hp...... it made 694hp.
 
you’ve totally lost me.

1.4cfm...... of what?
Carb flow? Head flow?
Does the number of cylinders come into play?



The thing is..... on the actual dyno, the motor didn’t make 616hp...... it made 694hp.

It's got nothing to do with carb or head cfm for just what an engine displaces in air at rpm, so a 589 is it's static displacement when off but at 5057 rpm the 589 actually displaces 1490227 cubic inches per minute or 862 cfm which is it's dynamic displacement.


It's just a formula I seen in one of my books seem ballpark enough to spec cid or rpm or hp which one your looking for or to compare different cid etc..
Should be for any amount of cylinders it obviously don't take in account for VE% I'm guessing the builder found that 1.4 cfm per hp is what average from his builds he did say something about higher out engines hp per cid use something like 1.3 or 1.2 I forget since 1.4 works close enough in my realm.


I seen that there formula was 78 hp short was the 5052 rpm at peak hp short to ?
the 1.4 rule of thumb says a 589 making 694 hp should peak at 5700 rpm ?
 
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15:1 580, 360cfm Heads.......
Calculator HP - 721
Actual HP - 828

As for the HP calculator, I just use the 1.4 cfm per hp rule of thumb and the cid x rpm/3456 = cfm, to get ballpark. So if I wanted a 400 hp engine that peaks around 5000 rpm would be 400 x 1.4 = 560 cfm so 560 x 3456 / 5000 = 387 cid.

828hp motor that peaks at 6400rpm.
828 x 1.4 = 1159
1159 x 3456/6400 = 625.8ci

But the motor is only 580”.

918hp motor that peaks at 6800rpm.
918 x 1.4 = 1285
1285 x 3456/6800 = 653.0ci

The motor is 572”.

This one is going the other way.....
420hp motor at 6200
420 x 1.4 = 588
588 x 3456/6200 = 327.7ci

Motor is 365”

Of course, that motor made 399.5hp@5100....... which shows it would need to be 379” to get it done.
 
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15:1 580, 360cfm Heads.......
Calculator HP - 721
Actual HP - 828



828hp motor that peaks at 6400rpm.
828 x 1.4 = 1159
1159 x 3456/6400 = 625.8ci

But the motor is only 580”.

918hp motor that peaks at 6800rpm.
918 x 1.4 = 1285
1285 x 3456/6800 = 653.0ci

The motor is 572”.

Think your talking builds above the 1.4 cfm rule of thumb, think it's mainly follows engine under 1.2 ish and under hp per cfm. Those engine you just listed are 1.43 and 1.6 cid hp per cid I imagine the torque to cid is way up there plus VE% BSFC etc...

The 580 would fall under the 1.3 cfm

828 x 1.3 = 1076
1076 x 3456 / 6400 = 581 cid

572 using 1.2 cfm

918 x 1.2 = 1102
1102 x 3456 / 6800 = 560 cid
 
This one is going the other way.....
420hp motor at 6200
420 x 1.4 = 588
588 x 3456/6200 = 327.7ci

Motor is 365”

Of course, that motor made 399.5hp@5100....... which shows it would need to be 379” to get it done.

Mopar 380hp 360 magnum create engine makes 409 hp

360 x 5400 / 3456 = 563 cfm
563 / 1.4 = 402 hp

Not meant to be 100% accurate though that's why we have dynos, engine efficiency are all over the place. Big difference between a 15:1 solid roller big port engine and a 9:1 rv cammed stock heads no formula gonna take that into account.

To me it just a quick way to ballpark something like eg... Say some one wants 425 hp 318 plug it in and says you need to make peak at 6500 ish rpm you decide thats to high and rather a 5700 ish hp peak plug that in find you need around 361 cid to do it.

In your world you'd probably use 1.2 or 1.3 or just your knowledge from previous builds.

0418c435-d2e8-4ae6-9bcb-dc15614c4166-jpeg-jpg.jpg
 
Like most quickie formulas, there will be combos where it’s close, and combos where it’s not really close at all.
The problem with all of them is, when do you know it’s wrong?

Since there are often “adjustments” that can be made to alter the results, that usually means someone is guessing about something related to what/if an adjustment is made.

Well, once the guessing begins..... the result can pretty much be whatever you want it to be.

But, as far as the calculator this thread is concerned, I’ll once again say that it seems to be the farthest off of any I’ve tried for any type of “racy” build.

It’s reasonably close on something like a 350 SBC with an RPM intake, E street heads, and a Thumper cam.
 
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Gave it a try on another mild build........ it was another “fail” imo.

The one in this thread......
Another very mild 440 build.....

The calculator shows 342hp@3700.

Tried a 10:1 street/strip 446, solid cam, Sidewinder heads, RPM manifold........ calculator is low by 107hp.
 
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Another one for ballpark I made up takes guesstimating the engines torque to cid ratio and where the engine peak hp rpm will be and torque at peak power will 90% of peak torque.

So if you where building say a 451 cid and figure the collection of parts your planning on using would make about 1.2 lbs-ft per cid and peak power around 5700 rpm.

so 1.2 x 451 x 90% = 487 lbs-ft
487 x 5700 / 5252 = 529 hp

So 529 hp @ 5700 rpm
and 541 lbs-ft @ 4300 rpm

Like you said there's gonna be a lot of wiggle room since you got to guesstimate two things and that engines torque will be 90% of peak torque at peak hp.
 
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How/where did you make the connection between the hp peak at 5700 and the tq peak at 4300?
 
How/where did you make the connection between the hp peak at 5700 and the tq peak at 4300?

Figure peak torque is around 1000-1500 rpm from peak hp, i just use 1500 as standard guess. Doesn't really have anything to do with my guess formula :)
 
Yup, guilty as charged! Everyone that sees my car and asks gets told it's "just a 440, not much hotter than stock. I just put loud mufflers on it"
:lol:
Yep. When people ask how big is your motor, i tell em its a hundred over 396. I dont tell em i'm talking cubes, not overbore. Not my fault if they assume its 415. (Its 496).
My 520 is gonna be a stock 413. I dont think very many will believe that though.
 
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My 520 is gonna be a stock 413. I dont think very many will believe that though.

You can tell people you ran the build through an on line calculator, and it said it should be right around 425hp.
 
Yeah, we have a quiet through the muffs street 440 that runs 10.3's@3800lbs:D
 
Yep, mine missed about that badly too. Out of seventy some posts, 50 or so say its garbage, so......
In my opinion, it's garbage.
Yeah. My example there is a ‘maybe later’ 440 I have. If someone really believed in this calculator though, results like this could really be discouraging lol!
 
452 c.I.
Dual plane
228@.050
250 cfm
7.8 dynamic
358 hp @ 3824 rpm

20+ years ago I built a 446 that was pretty close to those specs.
-446 with pistons down the hole .090
-bowl blended big valve 906’s
-9:1cr
-230@.050 hyd cam
-Original Torker
-650DP Speed Demon carb
-1-7/8” headers

I don’t know if I still have a dyno sheet for it, but it was in the 440-450hp range.
 
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