Horsepower Estimates

[VirginiaCityFord]

Can someone explain what the formula is to figure out how much horse power your engine should produce when your building it or doing add ons? For instance, the FE block 390 that I have is rated at 265 hp with a 3.77 inch stroke. I saw a rolling assembly that would increase the stroke to 3.92. How would I figure out what my change in hp would be?

[NUTNDUN]

I would think that if you are just comparing cubic inch by stroking the same motor with no other mods then you can figure out how much horsepower the motor makes in stock form per cubic inch and then how ever many cubic inches it adds from the stroke could give you a ballpark figure. Nothing is ever guaranteed. The other thing that you can do is find the program called desktop dyno and it will give a round about figure, it is all in the accuracy of the information provided. Comp cams also has a program to help figure out the camshaft and it could give a general idea as well.

I would think just upping the stroke to 3.92 from 3.77 would put it at around 300hp as long as everything else would support the extra inches. Now if you are going to go and add a wild cam and high flowing heads and intake and carb and exhaust you could put it up there pretty good.

[VirginiaCityFord]

yeah, the stroke thing was just one example I do plan other mild mods. I just don't know what the mathematical formula is to figure out any of this stuff, so I dont know where to begin with it. I do realize that there are no gaurantees, but it's fun to speculate.

[NUTNDUN]

Yes it is fun to speculate and bench race. I don't know what the formulas might be. A lot of it does have to do with the bore size and stroke to get your cubic inches and then the cfm the heads will flow at a given amount of lift, a cam that will make full use of the heads and a carb to feed it all. I think 300hp would be close for just a stroke and if you were going for more hp then torque a set of good flowing heads, a mild cam, a dual plane rpm type intake or a high rise single like a vic jr or super vic I don't see why you wouldn't be able to get close to 450 hp out of it.

[VirginiaCityFord]

Thanks for the help. I think what I am aiming for is a grocery getter thats a little hot. I'm think about some upgrades that will get better mileage and make it affordable to be a daily driver, but if I can at the same time make it just a tad hotter than stock that will be icing on the cake. I think I may go after that rolling assembly that will up the stroke, I've found an RV type cam that will help it in the lower rpm ranges, and from what I've read the low rise manifolds are best for what I am trying to do. I'm torn between trying to open up the ports on the stock heads and doing some things with the valves, or going aluminum heads. I'm also not sure what I am going to do with the carb situation just yet. Again, not building a beast, just slightly hotter than stock. The C6 is in good condition, but I want to have it gone through, that's a little beyond my talents, and I haven't checked to see what the rear end ratio is yet.