speedsense - 17 July 2009 12:19 AM

At 8200 rev limit, I seen 310's with 650 cfm carb, pushrod motors produce 775 hp at the flywheel. Dry sump oiling system. Roller rockers. Mod Cam.
At the rear wheels with a road racing Hewlin, carbon clutch 5 spd trans through a carbon drive shaft and 9 bolt live rear axle, produce 690 at the rear wheels.
Trans Am in 2001....they were faster cars when they could turn 9600 (mid 90's) though you could run the engine longer than one 100 mile race with the same performance change..
The 358 numbers were higher into the 850 range, though at the time were restricted with restrictor plates..
Considering that Nascar teams have triple to 10 times the budget and intense engine programs by comparison, the HP numbers should be way higher...

You have to remember that Cup teams are required to use flat tappet cams. NW, Trucks and ARCA can use roller cams. NOBODY would use a flat tappet cam for power if they didn't have to.
Also before NASCAR put the tapered spacers on NW and Trucks they were pushing close to 750hp in the high 8000 rpm range from what I heard. That's pretty respectable, unbelievable in fact IMO, from a 390 CFM carb.

red376 - 17 July 2009 08:19 AM

speedsense - 17 July 2009 12:19 AM

At 8200 rev limit, I seen 310's with 650 cfm carb, pushrod motors produce 775 hp at the flywheel. Dry sump oiling system. Roller rockers. Mod Cam.
At the rear wheels with a road racing Hewlin, carbon clutch 5 spd trans through a carbon drive shaft and 9 bolt live rear axle, produce 690 at the rear wheels.
Trans Am in 2001....they were faster cars when they could turn 9600 (mid 90's) though you could run the engine longer than one 100 mile race with the same performance change..
The 358 numbers were higher into the 850 range, though at the time were restricted with restrictor plates..
Considering that Nascar teams have triple to 10 times the budget and intense engine programs by comparison, the HP numbers should be way higher...

You have to remember that Cup teams are required to use flat tappet cams. NW, Trucks and ARCA can use roller cams. NOBODY would use a flat tappet cam for power if they didn't have to.
Also before NASCAR put the tapered spacers on NW and Trucks they were pushing close to 750hp in the high 8000 rpm range from what I heard. That's pretty respectable, unbelievable in fact IMO, from a 390 CFM carb.

Yes I'm aware and amazed at what the Cup teams have done in their engine depts, within their rule structure. Their pushrod technology is amazing.
Always wondered where they would be with over head cams, F.Injection, roller bearings...

Lol Yates has been pushing for OHC's for a few years, ever since he got involved with Grand Am... I've wondered tho, if that's only because he would be a step ahead(or two) of his competition

I know this topic started long ago, but I thought I would add my 2 cents.

Maybe you guys do know this, but I suspect most don't. NASCAR Cup engines are so well designed that they basically have the equivalent of a turbo or supercharger on them.

Let me explain...

VE,Volumetric Efficiency, is a key factor in producing power from an engine. What it means is that a 357 ci. engine running at 100% VE will move 357 ci. of air and fuel through the engine during one complete cycle. Typical VE of a sports car is around the low 80's. If you have ever replaced your entire exhaust, from the headers to the cat and the mufflers, I'm sure you noticed one hell of a difference. Doing that will bring a typical sports car up to maybe high 80's. Upgrade to a hot cam, higher ratio rockers, and redo your air intake (depending on the car, it may need a lot of work, or the stock air intake might just need a better filter), then you could get up to the low 90's. A new manifold, no cat or mufflers could get you close to 100% VE.

OK, we all can do this, so what does NASCAR do special? Well, this is why their engine builders make the big bucks... harmonic tuning.

At each track they will know what RPM band that they will want the most power (torque and horsepower) from. So they are able to tune the harmonics of the headers to actually suck the exhaust out of the engine. While at the same time, they can tune the harmonics of the manifold to actually force air and fuel into the engine. Yes, they are using sound waves to do this. So they are able to achieve VEs of over 110%... maybe even higher. 137% is the max for a normally aspirated engine though... and that's with using a lot of bells and whistles that NASCAR can't use... like overhead cams.

The latest numbers I've heard from NASCAR is that they are pushing about 900 HP flywheel. I'd love to see a dyno chart some day.

So, with just the VE aspect of the engines, it is easy to see how they can produce so much HP. Then factor in that they only have to make them last for 500 miles, if that, and you can skimp on the longevity of all the parts... even the oil. So it is no surprise that they can get 900 HP out of a 357 ci. engine. It's also no surprise why so many engines blow up.

PBFred - 04 November 2009 05:33 AM

I know this topic started long ago, but I thought I would add my 2 cents.

Maybe you guys do know this, but I suspect most don't. NASCAR Cup engines are so well designed that they basically have the equivalent of a turbo or supercharger on them.

Let me explain...

VE,Volumetric Efficiency, is a key factor in producing power from an engine. What it means is that a 357 ci. engine running at 100% VE will move 357 ci. of air and fuel through the engine during one complete cycle. Typical VE of a sports car is around the low 80's. If you have ever replaced your entire exhaust, from the headers to the cat and the mufflers, I'm sure you noticed one hell of a difference. Doing that will bring a typical sports car up to maybe high 80's. Upgrade to a hot cam, higher ratio rockers, and redo your air intake (depending on the car, it may need a lot of work, or the stock air intake might just need a better filter), then you could get up to the low 90's. A new manifold, no cat or mufflers could get you close to 100% VE.

OK, we all can do this, so what does NASCAR do special? Well, this is why their engine builders make the big bucks... harmonic tuning.

At each track they will know what RPM band that they will want the most power (torque and horsepower) from. So they are able to tune the harmonics of the headers to actually suck the exhaust out of the engine. While at the same time, they can tune the harmonics of the manifold to actually force air and fuel into the engine. Yes, they are using sound waves to do this. So they are able to achieve VEs of over 110%... maybe even higher. 137% is the max for a normally aspirated engine though... and that's with using a lot of bells and whistles that NASCAR can't use... like overhead cams.

The latest numbers I've heard from NASCAR is that they are pushing about 900 HP flywheel. I'd love to see a dyno chart some day.

So, with just the VE aspect of the engines, it is easy to see how they can produce so much HP. Then factor in that they only have to make them last for 500 miles, if that, and you can skimp on the longevity of all the parts... even the oil. So it is no surprise that they can get 900 HP out of a 357 ci. engine. It's also no surprise why so many engines blow up.

Your not far off, in Trans Am (also push rods) 310's were pulling 775 hp. at the flywheel... add a few more CI in there...and bingo..

It's funny that you mention a Trans Am (in a different context though). I'm not a mechanic, even though I sound like one, but I brought my '94 T/A back from the dead last summer. A blown head gasket, which costs about $4k to get fixed. Since I've been out of work for almost 2 years now, I decided to tackle the project myself... the most I could get for it was $100 and a free tow. So I figured I had nothing to lose, and plenty of time to work on it. Almost every mechanic will be impressed if you tell them you replaced the head gaskets on an LT1 engine in a Firebird or Camaro... basically because there is zero room to work on the engine. They even make special 1/2 height sockets just to be able to get the spark plugs in and out because of the lack of room. Book time for replacing the 8 plugs is 6 hours! Yes, that is how hard these engines are to work on.

I really did my research, and learned an amazing amount about engines. When it comes to the LT1 engine, I now know more about them than about 99% of the mechanics out there, especially because I understand the computer tuning side of it too. I've actually argued with mechanics about certain things, like they don't believe I can turn off the EGR valve(smog stuff) via the computer. Too many of them are stuck in old school (pre-computer) mode and even then, most haven't played around with all the computer tuning you can do. You pretty much have to go to a dyno shop to find the mechanics that do know the computers. And when it comes to performance upgrades, most mechanics know the basics, but they haven't really done their homework for the more technical stuff.

So my T/A is now pushing about 350 HP (stock is 270) and I can say this accurately without it being dyno'd based on the fact that my stock injectors are being max'd out. So until I replace them, I wouldn't gain much by adding headers except moving the torque band around some (I do have a high flow cat and mufflers). So injectors and then headers are next of my list to upgrade. But like I said, I am jobless, so it won't happened any time soon. But based on what I have installed, like higher ratio roller rockers, and basically all the "bolt-ons", I predict that once I do, I should be pumping out close to 450 HP flywheel... and this on a street legal car. Granted, I do have to reprogram the computer to pass smog. A 14.7 AFR is ideal for smog, but 12.2 AFR is ideal for street driving power.

One thing I should have mentioned in my post above is that a 10 psi boost (from a turbo or supercharger) will bring VE numbers up to around 200%. So the engines aren't truly performing as a typical boosted engine, but more like a mildly boosted engine... and no where near a race car boosted engine. Keep in mind that the higher the VE, the more fuel that is needed to keep the same AFR. So that is why boosted engines are usually a lot smaller.

Another thing they do is actually have valve over-lap... having both valves for one cylinder open at the same time. Seems stupid, doesn't it? In reality, because of the air flow creates a "flowing" effect, the exhaust rushing out pulls in the air and fuel, and vice-versa. Thus over-lap helps improve VE if done right too. There is a true art to getting these things correct. And as I mentioned, they only work good at certain RPM ranges. But stuff like this is why there is only a handful of teams building engines.

Split overlap has been around for a long time as have most of the engine tuning techniques described in your earlier post.

CFD simulations of intake and exhaust flow to aid intake runner, cylinder port, combustion chamber and exhaust header size and shape run for hours on end at Cup and other race engine shops.

These people are tuning each cylinder separately from the others in order to "balance" chosen power delivery curves. Oxygen sensors and temperature sensors in each header tube help with that - in the dyno room and during track tests.

Yeah, I never stated that anything that they are doing is new, just that most people don't have a clue about it. Even a high percentage of "gear heads" that mod their cars out for drag racing don't know a lot of these details.

It is also something NASCAR never mentions. NASCAR (no matter who is doing the broadcast) really talks down to their audience... explaining tight and loose every week and such. Hell, I think I might kick my TV in if I see that same animation of a valve breaking again. At least I haven't seen the "draft lock" animation in a long time.

They truly treat the audience like it is the first time they have ever watched a NASCAR race. Chances are that if you are watching a NASCAR race for the first time, it is because you are watching it with a NASCAR fan in the room. So they should be able to fill you in on the simple things like that. Even the talk shows don't go into much more detail than the race broadcasts. Hence, the whole reason this thread was started... how much horsepower are the Cup cars running? It seems like that should be a very simple question to answer, yet it isn't. And I've never heard a torque number given.

About the only time you ever hear any of the more technical details is during long rain delays in which they have to fill in hours worth of air time. And IMO, usually makes for some of the best NASCAR related TV.

Try this website:

http://www.racecar-engineering.com/

It's available in most decent magazine stores ... expensive, but worth it - cheaper by subscription. They have a large NASCAR section almost every month dealing with all technical aspects pertaining to the cars. No gossip, no nonsense tech only. You'll enjoy it.

Cheers.

red376 - 17 July 2009 09:36 AM

Lol Yates has been pushing for OHC's for a few years, ever since he got involved with Grand Am... I've wondered tho, if that's only because he would be a step ahead(or two) of his competition

Robert has called for 5 liter engines for years, also... at least at the plate tracks...