Hello,

I do understand I'm going to get burned for asking such an obscure question, buuutttt.....

I've been quite frequently bored (mainly I'm still a teen spirited senior that has hopes and dreams of being able to stick loads of money into these amazingly camaros eventually...)

I've had the bright idea for a few months now to just look up about Nascar engines (Not really wanting to build one, just curious what they put in the engines, always neat to learn something new.)

Well far as I am concern (correct me if I am totally and utterly wrong please) but far as I understand, that Nascar has had the history of having loads of rules and a huge one of them were that they had to choose an engine that is 358 cubic inches or less in size.

Is that true?

And how is it possible for them to get 700 to 800 hp out of these engines?

and what exactly parts would they use to get it up to that huge amount of power?

So far that's all I really know,

I have tried looking just about everywhere by surfing the internet, and sadly fail to find any much more information, maybe because it's not suppose to be told to the public? I really not sure I guess.

Again, with my un-ordinary questions, I like to come to this board, because I have met many people on here that has made things more clearing and understandable.



Thank you for anyone that replies to this,
Tim

 

These are engines with 100%+ volumetric efficiency. That means that the engine can move slightly more than its displacement in air when viewed as an airpump. This is usually achieved by properly tuning the intake and exhaust to allow the engine to move as much air as efficiently as possible. Things like tuned intake and headers and cam overlap allow an engine to do that. They also have high compression, high flowing heads, and minimal accessories. I would also imagine that a lot of work goes into the combustion chamber design as well. From my experience, thats where a lot of the power is made.

For enough money, you can build an engine that will do the same, but most of the stuff that gets an engine to run like that also means that it will be poor at street driving, and have poor emmissions. Large cams with overlap and emmissions equipment are not compatible with eachother.

 

Mmm, Defiantly true.
I guess I forgot about emmissions (I live up in the North East side of Montana, I don't believe we've had any troubles with emmission laws, if it was a problem, I don't believe the engine I have in my car would ever pass it. haha)

I can't really imagine what it would be like to drive an insane over cammed engine on the street.

(sure wouldn't make much friends with the police or neighbors.)

Thank you for the information.

 

Heres a discussion of GMs current R07 engine: http://www.autoblog.com/2007/04/16/g...nascar-engine/

Kinda neat to see how its designed.

Edit: if you take a look at the assembled engine, you can see how much larger the intake and exhaust ports are compared to your typical SBC head. These are larger with a much straighter shot at the intake valve, just like the newer LS1 type engines. A typical SBC head has an intake port that has a low roof with a somewhat sharp bend right before the intake valve. That impedes the flow of air and causes a pressure drop at higher RPMs, which reduces power output. The combustion chamber is neat, too. It looks more like a diesel with a flat deck and just intake and exhaust valves. The piston itself makes up most of the chamber.

 

NASCAR engines also make all that HP at 8000-9000 rpm

If you really want to scratch your head, look at the restrictor plate racing. We like to make HP with big carbs and big throttle blades. It doesn't necessarily make more HP but makes a flatter power curve. Your typical carb will have 1-3/4 to 2" throttle blades. A restrictor plate is under the carb with four 3/4" holes and the engines are still making 700 HP and running 180 MPH.

The 358 CID limit isn't a power restriction for these engines. Proper heads and cam grind can produce huge amounts of power in the rpm range that these engines run in but they are in no way considered streetable engines.

NHRA Comp Eliminator is no different. You could see a V6 engine in a tube chassis door car running 9 second 1/4 miles and spinning to 10,000 rpm.

 

Blah, that's crazy.

I guess anything is possible with the right knowledge how to do it.

 

Horsepower is torque multiplied by RPMs. Torque is pretty static for the amount of displacement you have. Displacement makes torque, it's the heads, cam, and induction that determine the power band and where it makes torque in the RPM range. You can make a v6 spin 10,000 RPMs and make a ton of power. Look at F1 engines, they're 2.4 liter V8's that peak aroudn 250-300 ft lbs of torque, but they make 900hp because they spin them to 18,000 RPMs to make that torque.

The catch here is that to make torque at high RPMs, it means your engine isnt tuned or set up well to make torque at lower RPMs, it's a trade-off. A lack of torque at the lower end of the RPM range makes for an engine that isnt fun to drive around on the street. You'll need a super loose torque converter or to run it at high RPMs all day long with a manual. Imagine having to spin an sbc to 3000-5000 RPMs just to slowly accelerate from a traffic light.

It costs a LOT more money to make a motor handle those high RPMs, and cost substantially more to do it reliably. The NASCAR engines have to last 500 miles and that's amazing considering how fast they have to turn all day long. You couldnt make one of those last 100,000 miles before a rebuild.

I will say that all bets are off once you start talking abotu forced induction. You bring a supercharger or turbo into the mix and it changes the playing field, because the motor moving far more air than its real world displacement would normally dictate. You can build a 700hp streetable 350 with no trouble if you had a supercharger or turbo on it. You're basically taking a 350 cubic inch motor and making it flow as much a 400 cubic inch motor, or a 500 ci motor, or a 700 ci motor depending on how crazy you go with it. You'd still lack a lot of low end torque, but you could make it managable, and it'd be significantly better at low RPMs than a naturally aspirated car of the same power level.

It's just about how efficiently an engine pumps air, and engines that are more efficient (forced induction makes an engine more efficient in this sense also) can make more horsepower without sacrificing streetability. An LS engine is much more efficient than a Gen I block for instance. You see 500 hp LSX motors alll the time, and you could drive those every day.

 

it cost around $60,000 for a hendrick motorsports nascar engine. millions of dollars in r&d and machining. its just proof what can be done with the right money,people, and equipment.

on another note they are looking into fuel injection.

 

Not all NASCAR engines make all of their power in the 8000-9000 rpm range. When they go to road courses, and the tight, short tracks at Martinsville and Bristol, the engines drop to low rpm's in the corners and have to torque these heavy cars their way back up the rev range. This is even more the case in the Truck and Grand National series that run on more of the shorter tracks across the country. The engines for these tracks still make BIG horsepower, albeit the big track versions will have a higher peak hp and less torque.

There are 55 years or more in developement in these engines, and very few if any stock production parts (going back to when they were making the original small blocks).
Besides the huge ports and valves already mentioned, there are many other tricks. Things like extra long rods, modified firing orders, special carbs, heads, headers and anti- reversion exhaust systems- the list goes on and on.
One thing that is pretty amazing is that NASCAR limits the top series to using flat tappet cam shafts to hold down costs and out of control speeds, I guess. Imagine how much more power and revs they could make with good roller cam profiles!

 

they use a block with 4.125 bore and 3.25 stroke. a 400 with 327 stroke. they use 2:1 rocker ratios to get over .700" lift. and they port the carbs. their 750 cfm flow closer to 900cfm. headers are 1 7/8 stepped up to 2".

 

For every 14.7 pounds of boost (lets just round that up to 15 for an easy number) you're effectively doubling the displacement of the engine.

Take a little 2.0 liter 4 cylinder engine. That's around 120 CID. Throw 30 pounds of boost into it and that engine is now the same as a 360 CID engine without all the excess weight of a V8. Now take a 350 V8 and do the same thing and you have the equivalent of a 1050 CID engine. Since the majority of all engines can produce 1 HP per CID, adding boost is like adding cubic inches. It takes a lot to put 30 pounds of boost into an engine so if you start off with a bigger engine, a little bit of boost is still better than a small engine with a lot of boost.

Volumetric efficiency plays a big part in getting more power out of a NA engine. It's all about how much air can be put into an engine. With boost either from turbos, blowers of NOS, it's an artificial atmosphere being put into the cylinders so they'll all have a high VE. A NA engine can only suck in as much air as the piston can pull in as it's going down into the cylinder. With good head design and cam grind, it's actually possible to achieve more than 100% on a high reving NA engine. The air moving through the head is going so fast that it's actually forcing itself into the cylinder before the piston can pull it in. This is only possible at high rpm. Usually 6000+ rpm.