HP per cubic inch

90limited · Jan 17, 2012

I always had the rule of thumb that if you can get 1 HP per cubic inch on a NA motor, you were doing pretty good. For example, NA 5.0 getting 302hp is great. Reason I am asking, is that when I see claims of a NA 5.0 getting 400 plus HP I tend not to believe it. Am I wrong?

srtthis · Jan 17, 2012

yes...

the coupe makes well over 900 on the motor and its 440"

wythors · Jan 17, 2012

Yes, you are.

1 hp/cubic inch was the benchmark for cars in the 1960's. That whole concept is totally outdated now. My very mild h/c/i 302 is right around 340 hp to the crankshaft and just under 280 to the wheels. A well-matched stroker combo is very easily capable of 400 horsepower. Hell, look at all the 300-horspower V6's being offered new these days.

Rick 91GT · Jan 17, 2012

If you are 2+ hp per ci, you are getting it done.. Got a NA 360ci , makes 750hp

90limited · Jan 17, 2012

wythors said:
1 hp/cubic inch was the benchmark for cars in the 1960's. That whole concept is totally outdated now.

Well that explains it, my data was from when I was a teen... Guess I am old... Thanks for setting me straight.

NIKwoaC · Jan 17, 2012

Yea, in this day and age, 1hp/cubic inch is weak sauce. Stinky weak sauce.

Gearbanger 101 · Jan 17, 2012

90limited said:
For example, NA 5.0 getting 302hp is great. Reason I am asking, is that when I see claims of a NA 5.0 getting 400 plus HP I tend not to believe it. Am I wrong?

The current 5.0L TiVCT does that and then some. It also does it with a silky smooth idle, gets cleaner emissions than any factory Ford V8 before it and knocks out almost 30mpg.

Thinks have come a long way in the last 40-years.

Mustang5L5 · Jan 17, 2012

These days...it's all about HP/liter...

NIKwoaC · Jan 17, 2012

Gearbanger 101 said:
The current 5.0L TiVCT does that and then some. It also does it with a silky smooth idle, gets cleaner emissions than any factory Ford V8 before it and knocks out almost 30mpg.

Thinks have come a long way in the last 40-years.

And yet people still want to run FRPP letter cams, haha.

CarMichael Angelo · Jan 17, 2012

wythors said:
Yes, you are.

1 hp/cubic inch was the benchmark for cars in the 1960's. That whole concept is totally outdated now. My very mild h/c/i 302 is right around 340 hp to the crankshaft and just under 280 to the wheels. A well-matched stroker combo is very easily capable of 400 horsepower. Hell, look at all the 300-horspower V6's being offered new these days.

Cant be that out dated Dave? What happened to that benchmark in the 70's and 80's? the 90's, hell, up until 2002? The "factory" benchmark was 1 hp per C.I in the 60's.
They must've forgot that formula in 1971. It took 40 years before they remembered.

In the aftermarket all the way up until the early 90's, a 302 played hell getting there.

Then the heads started coming.

85_SS_302_Coupe · Jan 17, 2012

Another thing to keep in mind is very few people actually have engine dyno numbers, most are chassis dyno numbers so for example my car put down 362hp at the wheels, so if you go by 15% drivetrain loss (most people say 15% for stick and 20% for automatic) then i'm roughly around 416.3hp at the crank. So, 416.3 divided by 347ci equals 1.997hp per cubic inch.

If you really wanna play with numbers, look into power to weight ratios. My car weighed in at 2880 a couple years ago, which comes out to 6.918hp per lb, which equals a power to weight ratio of 0.1445. By comparison, a 2011 Mustang GT has a curb weight of 3605 (for a stick) and is rated at 412hp (according to this http://media.ford.com/images/10031/2011_Mustang_GT_Specs.pdf) so the power to weight ratio would be 0.1142. The higher you get your power to weight ratio, the faster a car will accelerate. The cool part is you can get there by both dropping weight and adding power, so all out power may not be the most important thing if you can shed enough weight and visa versa.

wythors · Jan 17, 2012

85_SS_302_Coupe said:
So, 416.3 divided by 347ci equals 1.997hp per cubic inch.

Ummm...
416.3 / 347 = 1.19971182

hoopty5.0 · Jan 17, 2012

wythors said:
Ummm...
416.3 / 347 = 1.19971182

Hahah

tannerc91gt · Jan 18, 2012

I'd like to put my cars on your dyno

85_SS_302_Coupe · Jan 18, 2012

wythors said:
Ummm...
416.3 / 347 = 1.19971182

Well in all honesty i used a website for the ratio math so sue me

It's still better than the Coyote

Gearbanger 101 · Jan 18, 2012

NikwoaC said:
And yet people still want to run FRPP letter cams, haha.

Some still have that old school mentality I guess. If it idles lumpy, it must mean it's fast. I don’t know how many times I’ve heard guys at car shows quote “three quarter inch race cam” when giving the the rundown on their engine specs. I swear, some guys just regurgitate this old crap because they think it sounds good.

85_SS_302_Coupe said:
Well in all honesty i used a website for the ratio math so sue me

It's still better than the Coyote

It's too bad all that goes out the window when you consider how much ET can be lost or gained with traction and suspension. That power to weight ratio theory is only going to take you so far if he gets you out of the hole. D

85_SS_302_Coupe · Jan 18, 2012

Gearbanger 101 said:
It's too bad all that goes out the window when you consider how much ET can be lost or gained with traction and suspension. That power to weight ratio theory is only going to take you so far if he gets you out of the hole. D

Maybe maybe not, it just depends on how much of an edge the ratio gives you. Plus both guys can get better traction and suspension.

GT 00 · Jan 18, 2012

Well this mountain motor is 1005 ci and can make over 2000+ w forced induction I want that hell yeah!!! but it's roughly around 115,000 for the motor

85_SS_302_Coupe · Jan 19, 2012

GT 00 said:
Well this mountain motor is 1005 ci and can make over 2000+ w forced induction I want that hell yeah!!! but it's roughly around 115,000 for the motor

If you blipped the throttle it would flip your car over.

srtthis · Jan 19, 2012

GT 00 said:
Well this mountain motor is 1005 ci and can make over 2000+ w forced induction I want that hell yeah!!! but it's roughly around 115,000 for the motor

complete and utter waste of 115K to only make 2000ish hp...

HP per cubic inch

the guy doing it does every local racers rear end

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