how are they able to get 750HP out of a nascar engine? what are they 355?

 

by turning lots of RPMs, huge flowing heads and intake, large cam, and lots of money.

 

im sure that they use differents cams per track....but anyone know a ballpark of what size cams they run? how would the nascar engine do in the 1/4? I wouls assume they are top end motors? to be able to turn such high RPM's?

thise engine would not do good on the street? are they more or less a 1 time track motor?

 

I'm sure if you lauched them at 8k and had sticky tires and large gears they'd do very well in the 1/4. I have no idea how big those cams are, but I imagine the lobes are mushroom shaped. Their power curve is extremely peaky so yes it could be classified as a "top end" motorr. As far as street use, I'll bet those things idle sky high and they use race gas. But in street use I'm sure they wouldn't die easily if they last 500 laps at 9-10k RPMs.

 

They will use different engines at different tracks; although this is largely dictated by the event rules, they will setup similar engines to best fit the many variables of the race itself.

As far as driving around such an engine on the street, it would not be smart. These engines don't cruise at low RPM. Although some races call for an engine that might be more suited to driving on the street, it is still designed for it's intended use—stock car racing! Generally, these engines have huge valve lift values and giant ports and valves for the displacement at street crank speeds. Then, consider the small chamber size.

 

alot also depends on the gearing, when a car is setup to be running 190 mph, its performance off the line is somewhat diminished. A stock car with a street gear in the rear end would probably run a mid 10. On a track setup theyll prob run a low 13

 

Download Crane's master lobe catalog. It's got NASCAR grinds in it. It'll give you an idea. Mostly lots of duration and a ton of lift. That plus mega rpm equals horsepower.

 

About 10 years ago I saw the "Interstate battery" NASCAR run an 11 something 1/4 mi. in stock car trim. This was in Chevy High mag. I think.
Steve

 

in unrestricted qualifying trim, the engines are closer to 900hp now.

Just imagine if they weren't limited to 358cid, 12.0:1 compression, and flat tappet lifters...

 

Can't speak for the cam but they are very top-end I will try and get a dyno sheet to post when I get back in town (approximately 1 week)
They are typically 1 track motors but they are still useable after that one time, and you can usually buy them for much less than they originally cost. But they do have quirks. The ports are so large and the walls of the ports are so thin that is not uncommon for them to have chunks of the ports disappear after extended useage. The rotational assembly can hold up quite well for extended periods the weakest point by far are the pistons. I've seen one go through several sets of pistons but the crank and rods are still good. Everything in them is VERY expensive. The engines are mostly titanium and aluminum with very little steel apart from things like rings, cylinder walls and whatnot. Almost all of the fasteners are titanium, the valve springs the valve spring keepers, all of that is titanium. If you want you can pick up an engine thats close to one for around 30k new from jaydickens.com, but if you want the full NASCAR build, expect to pay much more, last I heard it was closer to 50 thousand.

 

I'm not sure where you get your information, LiE, but some(?) of it is incorrect.

FWIW, much of the info in this thread so far is less than correct. There are a lot more steel parts in a Cup engine than many would imagine; some because of rules, some because of what works. For some tracks, the usable rpm range is over 4000 rpm. That's not a "top end only" engine. For plate tracks a 300 rpm range is about right.

 

was the little that I posted off by much? I heard 2 years ago that the Yates engines were hitting 10,200 in unrestricted qualifying trim. Naturally they dial things down a bit for the race to keep things alive.

 

The information is regarding an engine that came into a shop I was working at some has been changed but for the most part it was the same as when it ran on the track. I was also purposefully vague as A) the engine is still being used on a different track and B) Some stuff that I know I'm not sure jay dickens and co would appreciate being given out for free.

 

Cup has gear rules (when NASCAR needs to impose them) to keep the max revs around 95-9700. 850 ish hp is probably a lot closer than 900. I don't believe there is (allowed to be) a whole lot of difference between race and qualifying engines. Rocker arm ratio and probably springs, and maybe intake manifold. They can't go inside the engine as far as I know.

Yes, I believe 10K+ was being used, and that's why the gear rule was imposed. Some teams were hitting 10K in races I believe. #2 and #12 come to mind.

Flat tappets aren't all that much of a problem today. They have some advantages over rollers, and also some disadvantages. Coatings have helped a lot.

I believe all of thses things must be steel:

crank, rods, valvesprings, pushrods, piston pins (?)

Some of the things that may be steel in some team's engines:

camshaft, valvespring retainers, rocker arms

I suggest that some of the steels used are very exotic.

 

It's not just the cup engines getting cool toys. The dirt track scene has its share of exotic stuff too. I've seen 32lb cranks and 11,xxx rpm in qualifying already this year. When it gets to that level, it's all in the engine builder and their precision.

Dirt Late Models are so much more exciting to wrench on and watch anyway.