I have a 350 cubic inch engine, that gives 350 HP. That's 1 horsepower per cubic inch.

Modern cars do a hell of a lot better than that. Some produce over 2 horsepower per cubic inch. Where does that power come from?

To me, this is amazing. Especially considering that (1) they have to deal with emissions control, I don't, and (2) they are measured in SAE net horsepower, while mine is measured in SAE gross horsepower, making theirs look lower by comparison.

Some of the reasons I can think of include:
1. Turbochargers -- these add significantly to HP
2. Fuel Injection
3. Engine Management Systems, controlling timing and fuel --- seems to me a fine-tuning, not a huge power gain

I know I must be missing something significant.

If I change out my cam, intake manifold, exhaust headers, and other parts that might not withstand the higher torque, I can marginally improve my HP, maybe up to 400HP instead of 350... but certainly not 700HP (2 HP per cubic inch).

Don't get me wrong -- I totally believe "there is no replacement for displacement", and that the type of power I'm getting is raw, mean, consistant, and high torque. Still... I can't help but wonder. A lot has changed in 27 years... is there any good stuff that can be adapted?

 

Fuel management and head design. The heads are where power is made. The ports and comustion chambers are so much better on modern heads than the old ones. Also roller cams are much better than the old flat tappet. They are expensive but will always outpower a flat tappet.

 

Yep....heads are where the power is..the rest just has to stay together!!

Heads, roller cams, induction and fuel management pretty much in that order.


JIM

 

Variable valve timing, computers, injection. All these goodies have taken over the car world for a reason.

Like said before, heads are a huge part of it.

But I have to say, I'll take the sound of my small block over a variable valve timed rice rocket any day.

 

heads and induction are big ticket items nowadays on modern cars. other than 4 bangers with chargers, who really makes 2 hp per ci? would always choose the torque of a big v8, over any hi rev 4 banger out there. love to be laid back in seat, these new cars have a hard time doing that

 

Yes the power,fuel economy,and comfort of the new vehicles are light years ahead of our old favorites.UNTIL you get the repair bill for one of these technological wonders!

 

Boost is absolutely a replacement for displacement. My 183ci car makes 800+rwhp... only possible through boost .

 

Since heads are a major item, is there a sbc (gen 1) head out there that has an efficient combustion chamber--like swirling or squishing better than the late '60s/early '70s? How are the Edlebrock aluminum heads? What mods do you have to make to accomodate roller lifters?

 

I agree with the others - most of the heavy lifting has been done through improvements in head design.

Actually, it's pretty commonplace to have small blocks with 700hp. Guys with twin turbos have ones putting out more than 1,000hp. You can easily bolt on parts to hit your mark...just like the auto manufacturers do.

Also, pay attention to the speed at which the hp of modern cars are rated and the size of the engine. For example, Honda rates its S2000 hp at 7,800 rpm. Since hp is based on rpm, the faster the rpm, the higher the hp. It's easy to rev a small engine to get high hp per cubic in. But the lack of torque makes it doggy on acceleration. So hp alone doesn't always tell the full story.

 

Technology my friend, technology!

 

Thanks for all the great replies. I love getting skooled!
I was wondering if anyone had done turbos... 1000hp is shocking. I had no idea about the heads... my system is all old stock heavy cast iron stuff... do you think I'd do better to swap out my heads? and if so, for what?

At risk of going off of my own topic now...
My '69 coupe has seen very little use, but very little service as well, something I hope to change. Right now from the line, if I slam on the gas it slowly musters the strength to get moving, something I absolutely abhor. Once it's up to 20 or so, if I push down the pedal, the front end lifts up and it really pulls nicely. So something is clearly limiting my power initially... I'll have to rebuild and tune a lot of stuff to find out why. I did the timing (ala Lars paper), and am going to rebuild the carb sometime soon.

Worse even than the sleepy performance, the car seems to bounce all over the road. If I put on the gas a the wrong time, I might be pointed the wrong direction! Before I get any more power, I've gotta make sure the tires are pointed straight, and the suspension and handling are solid. I'm looking at a composite spring in the back, polyurethane bushings, gas shocks, soft front springs and thick anti-sway bars all around. Does that sound about right?

 

Actually, a lot of it has to do with the RPM that those little 4 bangers can turn. Horsepower is just torque times RPM divided by a constant.

HP = TQ x RPM / 5252

The Fall 2006 issue of Engine Masters magazine has a great editoral about this.

Basically, to summarize, a good street engine using today's technology can make 1.2 to 1.3 lb-ft of torque per a cubic inch (1.3 to 1.4 for a race engine). So, on with the examples.

Lets say we have a great 327 motor and it makes 1.25 lb-ft per a cubic inch. That works out to be 409 lb-ft of torque at the peak. If we build it to peak at 5500 rpm, we get 372 hp. 6500 prm gets 440 hp and 7500 rpm gets 508 hp.

Now, lets say we build a 454 cube small block and make the same 1.25 lb-ft per a cubic inch. We now get 565 lb-ft of torque. 5500 rpm now gets us 515 hp. 605 hp at 6500 rpm and 700 hp at 7500 rpm. The 327 could make 700 hp but it would have to spin to 10,500 rpm!

Of course, all these numbers are based on good flowing parts and naturally aspirated. What flows well for a 327 would choke a 454. And, forced induction throws everything out the window.

Basically, what I am saying is that I don't care that an S2000 makes 200 HP at 8000 rpm or whatever. Torque is what you drive on the street and a well built small block is a lot more fun than any four banger.

 

If you have enough money...1000 hp from 2.0L.

http://www.thecarconnection.com/Enth...247.A5482.html