Is there some kind of formula that calculates the maximum amount of power a motor could make based on factors like cubic inches, fuel octane, etc??

Is there some kind of theoretical maximum the 420A motor can make N/A?

I'm sure you'll reach a max somewhere, but it's pretty much limited to money.

Originally posted by cougar694u
I'm sure you'll reach a max somewhere, but it's pretty much limited to money.

Not really though...you can only make so much fuel and air go into an N/A motor. You can upgrade the fuel, upgrade the type of fuel, ie Methanol, upgrade the compression, but you can only squeeze so much power out of it.

I'm not only looking at this for a 420A application, but like a small block 350ci motor...how much can it make n/a? Any formula?

there is a way to know I don't know if its an exact formula or not but it requires using a flowbench ummm...here is an article that explains it a little more its a diff vehicle but same principle i would think.(this came from www.mazdatruckin.com):

A flowbench is sort of a big vacuum cleaner that is built in a way to find out how much air something flows at a given pressure drop. It is the only way to effectivly modify the cylinder head ports, valves, intake manifolds, carburetors and anything else in the engine that flows air and know that you may be doing good.

For instance at school I braught in a stock B2200 cylinder head, intake manifold, and a holley 5200 carb off of a 78 VW.

After putting everything on the flowbench I found out that the stock intake ports flowed 149.076 CFM at max valve lift. Each intake runner on the manifold flowed between 152 and 160 cfm. The carb flowed about 180 CFM. All of this was done at a pressure drop of 28 inches of water.

Some engineers somewhere after many dyno runs came up with the formulation that at 28 inches of water the horsepower any given part that flows air can provide is the CFM/4. This is if every part in the engine is completly optimized for performance. So now you know that the maximum hp the engine could ever make (without boost) would be about 150 hp unless you modified the ports and the intake manifold. The carburetor only flows 180 CFM which is sort of ok considering only one cylinder is going to pull in air at a time so technically it only needs to flow about 150 cfm to keep up with each cylinder. Unfortunatly as air velocity increases really the carb tries to feed atleast 2 or more cylinders at one time because while the intake charge for one cylinder is trying to start the one before it is trying to stop. So now we know that the Holley 5200 does not flow enough air to support maximum horsepower on even a mostly stock engine.....

Now lets say we want to modify everything so that it makes more power. I modified one of the intake ports on the cylinder head. I didn't do anything drastic just smoothed out one area of the port. When I reflowed the port I killed the flow by 20 cfm at max valve lift. The modification I made that I thought would increase power a little actually just potentially killed 5 hp. The intake manifold I didn't do any modifications to except cut the vacuum ports down level with the ports. When I reflowed all the runners instead of them flowing between 150 and 160 CFM they now flowed between 158 and 160 cfm. Since now all the intake runners are flowing almost exactly the same amount of air, if the ports in the head are doing so as well that would tell me that the engine should run very smooth and probably make better power because everything is balanced and each cylinder is not fighting the other.

Of course there are other things it can tell you as well such as velocity, percentage flow ratios, and booster signal in carburetors. You can have ports that flow all the CFM in the world but unless they have velocity they will not make any power. At the same time if you modify your carburetor to flow more air and you test it and the booster signal has decreased you know you probably just killed power instead of making it.

Realistically without a flowbench most modifications you make to the ports of the cylinder head, the intake manifold or carburetor are a complete stab in the dark. If you know what you are doing you can make modifications that are garanteed improvements but these areas usually give you small gains compared to what you can do if you have a flowbench.

Umm.... If I lost anybody a flowbench is used to see how much air something can flow, lol.

Edited by Kyrasis6 on July 20 2005,8:22

The Stratus touring cars had a 420A that was making something like 300hp. This is on a fully built engine all the toys and goodies, lots of dyno time and custom parts. If you don't know how to design an intake manifold or headers, and have the patience and resources to take several designs to the dyno, you'll be lucky to see 2/3rds that power level.

All engines react differently to different mods, I know of mo claculation that will ever tell you max power. There's far too many variables.

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Go that way, really fast, if something gets in your way... turn.

The easiest way to tell is to look and see what other people have done with the motor. the 350ci small block, especially if it is a Chevy, has been built up tens of thousands of times, and numbers are widely available.
The most power I've personally seen an all-motor 350ci make was about 600 horsepower, and it was not very streetable. It revved to about 8000rpm, which I didn't think was possible with a pushrod engine. It was definitely fast, but needed gas blended to around 97 octane.

I'm pushin about 480 at the crank with my 351 w, but I have to run like 108-112 octane. Other than that, it's streetable. My motor's very mild compared to many I've seen. I'm still runnin hydraulic flat tappet lifters, too, and I can turn almost 7000 RPM, but I shift at 6300.

My 350 bored .40 over is pushing some high #'s. Once she comes back from the dyno sometime next week I can provide a detailed list of each and every internal component and what the #'s are officially.