How to calculate my HP

[fuccillo111]

Hi guys. I've completed my Chevy 350 build and need some guess at HP. If someone here is good at this stuff I can post key components to help add the power up. I'll start by saying it a 68 or 69 four bolt .040 over, double hump heads w fresh valve job. New scat crank. Comp cam(280, .480), comp pushrods, Rhodes hydrolic lifters, aluminum rollers, weiand street warrior intake, edelbrock 600., stainless long tube headers, 2.5" exhaust, th350 w transgo shift improver, 7.5 posi 3.73...any help is appreciated. Thanks.

 

[pontiacgp]

why not put it on a dyno...

 

[oldmansmonte]

If it sounds like it's running right with no issues you should be floating around 350 at the crank. That's if I was a gambling man, which I am not

 

[MrSony]

Once you get it in a car if it's not already, go to a chassis dyno. Yeah sure it's fun to wag your engine dyno sheet at everyone but it don't mean sqaut if your motor makes *** at the crank but only puts half to the ground. I calculated mine by having an educated guess and some basic math. 1/4 mile times tell all. 15 seconds flat at like 90 or 95 with a 3500lb car with a three speed th350 works out to about 250 crank hp and about 200rwhp.

 

[fuccillo111]

Once you get it in a car if it's not already, go to a chassis dyno. Yeah sure it's fun to wag your engine dyno sheet at everyone but it don't mean sqaut if your motor makes *** at the crank but only puts half to the ground. I calculated mine by having an educated guess and some basic math. 1/4 mile times tell all. 15 seconds flat at like 90 or 95 with a 3500lb car with a three speed th350 works out to about 250 crank hp and about 200rwhp.

It would be interesting to see how close your numbers are to a dynos numbers. The reasons I havent dyno'd mine: the build seems pretty mild and basic and thought a lot of people could guesstimate pretty close as a result of doing it their self's. Another reason is I havnt heard of any dyno shops around my area. Last is I would feel silly bringing my car there. I always figured dynos where for extreme builds and tuner cars.

 

[Kwik_Cutty88]

You shouldn't feel silly putting your car on the dyno. It's your build, be proud of it! Who cares if it flops and doesn't make the number you want, you built it, enjoy it and be proud of it!

 

[MrSony]

Yeah don't feel dumb or silly for wanting to know what your hard earned cash has done! I am itching to get up the 100 or so bucks for a whole day of dyno tuning and tweaking. They have so many more tools and so much more knowledge than one would think. They can time your engine exactly where it needs or where you need, correct your air fuel ratios, all kinds of things that are made so much easier in a shop.

 

[pontiacgp]

the guy that works the dyno usually tweak the car to get the most out of it and they'll make suggestions on how to get more performance with what you have so it worth the money to do it...

 

[CWPottenger]

Have you run it in a qtr mile yet?

If you want just a ballpark figure. Horsepower = Weight/(ET/5.825)3
This is just a very broad/general figure that assumes all things equal(they are NOT)...


I would agree though a dyno session by a good shop is worth every penny and they will help you get best performance and/or driveability out of your combo

 

[fuccillo111]

Have you run it in a qtr mile yet?

If you want just a ballpark figure. Horsepower = Weight/(ET/5.825)3
This is just a very broad/general figure that assumes all things equal(they are NOT)...


I would agree though a dyno session by a good shop is worth every penny and they will help you get best performance and/or driveability out of your combo

No 1/4 yet. To be honest it wasn't built to run 1/4s but that doesn't mean I can't. I think I'll look for a dyno, you guys talked me into it 🙂. I want a baseline for now as I plan on upgrading the heads and possibly more over winter. 450hp would be nice to squeeze out of this motor...somehow.