Technical Horsepower calculator

Need some help trying to figure out horsepower calculator I'm lost trying to figure out how to use it

 

Have you tried this one?
http://www.wallaceracing.com/et-hp-mph.php

 

Trying to find the horsepower of a engine

 

What are your inputs?



The diesel guys can calculate peak power based upon the amount of fuel injected and duration during the power stroke. Bit tougher to do the same with a gasoline motor.

If you are starting a bit more basically. Multiply by 0.85 for friction and other inefficiencies.

 

Here's another very basic one....... https://www.gofastmath.com/Horsepower-Calculators/Horsepower-Calculator

 

Which engine? You gotta have some information to start with....what information do you have?

 

Number of window stickers times 5...?

 

I will get all this morning for you

 

Hello,

Those guys at Wallace Racing.com did a great job with those graphs and charts that miraculously show what your horsepower would be with weight and E.T. as well as filling in other facts. It sure was fun filling in those blanks to see how our original SBC motor and Willys Coupe build rated against the chart facts. For the most part, it is an average of facts built in to the computer program. It does not take into account the actual build with specific speed parts. It seems like it is based on a standard motor, such as a SBC motor in any hot rod.

The basic facts about weight and E.T. times are facts, but, the computer does not take into consideration that the motor with all of its precision racing equipment and tuning can result in higher horsepower for the build. So, the results are not specific to your build. It was fun filling in various facts and seeing the results, but the results aren’t always correct.

We had two SBC motors in our 1940 Willys Coupe builds. Chevy running gear, LaSalle transmission and a lot of aluminum sheets were used in the first build. The first edition was a 283 with 6 Strombergs an Isky Cam and kit, Jahns pistons, as well as Chevy truck heads. It turned 13 sec on the initial quarter mile run and stayed at that average speed for a couple of months. It did not matter what we did, other than getting better at the starts from the line. we were limited with the build.

Similar to our 671 292 SBC motor with Isky Gilmer drive

When we decided to get a total rebuild with the same 283 block, but go up to 292 C.I. (with all blower spec crank, pistons, rods, a Howard Cam/kit, plus a Joe Hunt Vertex Magneto, a new 671 supercharger with an Isky-Gilmer belt drive… headers) using the same 6 Strombergs that led to some serious horsepower. We knew it had more horsepower and the times were much better at 1 sec faster. When we added welded in weight to lower the qualifications for the C/Gas class, the new 292 671 SBC motor started making some great runs and we were getting close to the national record.

But, for all of the work we did on the 671 SBC motor in the 1940 Willys, to get in a good position for a run at the national record, we had no idea what our horsepower was for the final build.

Jnaki


We never knew back then, so recently, I used the Wallace Racing Calculator with the established weight and E.T. times to have the results come up with a whopping 270 horsepower from our 671 full blower spec motor on our 40 Willys Coupe. What happened to the rest? And how much was the actual HP rating? We can guess based on other similar builds, but it is only a guess.
This build only made 270 HP? What? YRMV
https://www.jalopyjournal.com/forum...the-best-gassers.1015973/page-6#post-14265753

 

There’s also several “engine dyno” calculators as well (may have been listed above) where you put in the cam specs, CR, etc and get an estimate. Is that what you are looking for, or based on the vehicles performance?

 

Chevy 406

9.8 compression

251 .050 exhaust

243. .050 intake

515 lift

304x296 advs

Roller camshaft

.039 head gasket

.020 deck clearance

202 x. 1.6 gm bowltie heads 64 cc

Dual plane intake

750 holley carb

 

With the bore and stroke and cam opening/closing specs and if it is solid or haydraulic, I can put that info into Desktop Dyno 2000 and it will give a pretty good figure on the HP and Torque it should make.

I have found it to be a pretty accurate program. Comparing those readings to actual results using Wallace Racing figures..... they both show close to same figures if you account for power loss thru the drivetrain.

 

Something I've been doing for the last ten years is actually dynoing my engine's. Knowing the highest HP is usable for bragging rights but the HP and Torque curve is what I'm looking for.
There's no way for a calculator to distinguish between a small block that makes 450 peek hp with a narrow power band and one that makes 450 peek hp but makes 400 ftlbs of torque at 2800 rpm through 4800 rpm and over 400 hp from 4500 rpm to over 6500 rpm.
Two 450 hp small blocks but one is going to be faster so the power calculators are going to be incorrect at least once.
On engine masters they figure average power over an rpm range not just peek power. This gives a better understanding of the power being produced. But if your looking for a number the calculators will give you one but it is more of a ballpark figure.

 

oldiron -

While what you say is correct for the cheap / free calculators, there ARE other computer based "dynos" that will provide the entire power and torque curve AND, are actually fairly accurate, IF...the input is accurate.
BUT, much more info than is given above is required. All the way into the fuel type, test altitude, etc.

Mike

 

When I plug in the e.t. / mph / weight in the Wallace calculator for my car it's actually fairly accurate. I'm also taking in account for my power sucking C6 trans.

 

Here's ten bucks well spent:

 

The program I have has a lot of inputs to get real accurate results. It will print out a graph showing HP and torque, VE, dynamic and static compression..... loads of info.

But like was said.... all the input info has to be there and accurate.

 

oldfart, based on your info, you must have started with a 400 cu. in. small block, correct? My guesstimate/w bowtie heads would be about 400 hp, or 1 hp per cu. in.

 

There are fairly accurate algorithms these days. There is even one that is pretty close if you make a pass for a given distance and plug in your ET.

None of them beat a few pulls on a dyno for accuracy though and dynos are not as accurate as we would like.

I used to tell people that I could get pretty close by having the parts list of the build. That was until the later 90s when I screwed one together that made almost 30 HP and a bunch of pound feet more than my estimate. I was not disappointed obviously but it made me rethink the theory of synergy for damned sure.

 

Look above your post

 

That cam is going to pull untill about 6000 rpm in the 400 with the bowtie heads, I'll throw in my s.w.a.g. at about 425 hp

 

Thanks when I did it with one chart it was 327 hp

 

Looking at specs for 383 strokers should give you a pretty good idea what to expect. They are much more common that 400 small block builds. Although I did have someone disagree with me, the 400 small block has thinner walls than the 350, which can/has resulted in cylinder wall distortion. Unless all of the 383 strokers out there are using aftermarket stroker cranks, you have to ask why they are using 350 blocks in stead of the 400. I can't imagine there were a lot more 400 cranks made than 400 blocks.

 

By the way, my dad was the original owner of a 1978 Jimmy/w 400 small block. Other then removing smog and adding headers and dual exhaust, it was completely stock. He didn't take it off road or pull a trailer. It did use oil. When he sold it, the buyer said he was going to put a 350 in it.

 

383 is a 350 block with a 400 crank or aftermarket crankshaft

Yes the 400 has less thinner walls then the 350

 

400 crankshaft are harder to fine I could not find a good one so I bought a scat

 

It would be a neat academic experiment to dyno a car then run the hp calculator to find out how close it comes out.

 

It becomes very academic. There are simply too many variables, even with just an engine dyno. Throw in the whole drivetrain, and the amount of variables grows exponentially. I did this many times at my last job, the engine designers would run their latest design through their calculators (expensive software that typically only OEM's can afford), and turn over the prototypes to my Test Group. We would run the engines through their paces on either the engine dynos or chassis dynos and collect a boat load of data (100's of channels of data, sometimes at 1000's of data points per second). Atmospheric changes alone could play havoc with the numbers, even in multi million dollar dyno cells with very good climate control systems. Fuel variability was another huge concern. We used pure isooctane to minimize this, but even so, it could vary from barrel to barrel. If we were within 10% of the software, it was considered a huge win.