what would you have to do to get an engine to rev to 7000-7500 safely? i'm thinking forged crank, rods, rod bolts,forged pistons, and balancing. what else do you need to do to get it to safely rev besides the valve train? would a 2 bolt be ok to rev that high safely?

 

rods and crank is what takes a beating on a high reving engine, make sure u have a good lubrication system too.

 

If I were to do that, I would like a 4-bolt. Question: why do you need/want to go that high? Why not make gobs of power like between 3000-6000?

 

build a 327, those are really rev happy engines, i was just at a dyno saturday with a friend with a 327 in his bird, he took it to over 6k each run in 3rd and over 135mph. sweet engine.

 

4 bolt main is a must for any high revving engine, replace the mains with something bullet prof.

Then go to forged everything.
and a valve train setup for it as well, you would most likely need solid lifters DON'T GO HYDRAULIC

Take a look at what they put in 68-69 302's they where good for 8K

 

I second Drakar, Hydraulic lifters will tend to float around 6500rpm. And forged everything with 4 bolt mains. Just agreeing with the others on it. That is a whole lot of rpm's. Are you building a circle track engine?

 

the 67's will do it too but ther not as happy my dads 69 peaks at 6800 so it gets shifted at about 7300 most of the time

 

you'll hear a lot of talk about 302s and 327s being faster spinning engines than other SBCs but don't believe it. there isn't much about the bore or stroke that allows an engine to spin as much as the ability to move air in and back out quickly. besides a good induction and exhaust system light weight parts factor in to higher rpm engines as well as quality forged parts do.

 

i am not trying to be an *** but i think you are a bit mistaken. with the same set of heads intake and headers a small stroke motor with the same bore will rev much more freely than a motor with a longer stroke. yes it will not make as much torque. on the other side with pistons that all weigh the same the ones in the small stroke motor will place alot less force on the rods and crank due to less momentum.

 

It's not really a problem of RPMs but rather FPm (feet per minute) of piston travel thats the problem.

For a stock small block 4000 fpm is considered max.

4000fpm=48000 inches per minute of piston speed

example a 383 has a 3.75" stroke so 3.75x2=7.5" so 48000" = 6400rpm max safe piston speed if the parts are in great shape and valve float does not occur first.

example a 350 has a shorter stroke, so with that engine we get 3.5 x2=7" 48000"/7"=6857 rpm

see how it works? now you can raise the rpm level to about 4500fpm if your useing racing style all forged and ballanced parts

4500fpm=54000

302cid = 9000rpm

327cid = 8307 rpm

350cid = 7714rpm

383cid = 7200rpm

Hope y0ou get it!?

 

Like Ede said, running hellacious RPMs has absolutely nothing to do with an engines bore x stroke and everything to do with it's intake, exhaust and cam. You can make a 383 spin 7k+ just as easily as a 302. All you need are good heads and a cam that will make power that high. Simple as that. Short strokes are for class racing and losers. Everyone else runs as much displacement as they can find.

Sure you can debate piston speed, etc but the solution to that is a good bottom end and valvetrain.

 

what exactly do you mean by 'rev more freely'. Yes, a smaller displacement engine can run higher rpms than a larger displacement engine using the same parts. Example, say at 6000rpm a 350 is using x amount of air, and has maxed out the heads/intake/exhaust. Destroke it to 302, and at 6000 rpm it will use less than x amount of air--so you can rev it up higher. The problem is that the 302 needs to rev higher to match the amount of air into the engine. The amount of air/fuel that is used by an engine is directly related to power output. "People" stroke engines, like the 350, to gain power and make their car faster--and it works. Destroking it has the opposite effect. As far as being reliable, circle track 350's often last all season running 8500rpm--no one runs less than the maximum displacement.
What does it take to run 7000-7500 rpm on a regular basis safely--money and an experienced engine builder.

 

I think two different things are being debated here anyway.

• The ability of an engine to get up to and make power at a higher RPM
• The mechanical ability of the engine to handle spinning at said RPM

The better answer to the original quiestion is basically going to be a combination of the above arguments.

 

Best bet, larger bore short stroke, like the 302 and an all forged lower end. And as mentioned before, solid roller valvetrain.

 

what about a 400 with a 3.25" stroke that would be about the same as a 350 but i bet it would stay together alot beter with a set of good caps

 

well actually i want to disagree with the part about 4-bolt mains, it doesn not matter, a stock 2-botl cant hold 4 to 5 hundred HP without a problem, now with splayed 2bolt caps you should be find, and a 327 is a more happy higher revving engine because of its shorter stroke.