What helps RPM's?
 

I am looking at changing my valve springs,cam in hopes of getting a 7-7500 rpm reliable engine. Do i need a lighter Crank,rods,piston or is it mainly the cam and springs. I do know all help but can you pick up more RPM's from cam and springs or by the balancing?

Re: What helps RPM's?
 

Bottom end in your sig should be fine upwards of 8K RPM. I would recommend Isky red zones with a solid roller cam, and aluminum roller rockers. Of course you need high flowing heads to hit 8K.

Gearing will get you there also, but may slow you down at the same time...LOL


Check out this site for BBC advice!

http://www.chevelles.com/forums/forumdisplay.php?f=13



A.........

Re: What helps RPM's?
 

462" takes a lot of piston swinging around, and a lot of stroke. It's the crank forcing all that heavy weight to change directions that typically rips a rod cap off or piston pins out of a piston. I'd be cautious on the top end when you snap the throttle closed.

Myself I'm not a fan of the KB piston line. Do you know what they weigh? As a comparison a typical JE BBC 460 flat top is in the 550 - 590gram range. Whatever you do, when freshening the motor take special note of the piston pin bores.

Re: What helps RPM's?
 

Gearing will not "change" operating RPM of a motor.


Operating RPM is typically a function of cam timing. There are other things that can hold RPM back like intake manifolds and headers that are not appropriate for a given combo. But in all reality it is a combo, and needs to be thought of that way.

Generally speaking and cam with a later intake valve closing point and more overlap will spin more rpm.

To Marv's point, piston speed can wear on bottom end parts very quickly. The heavier the components the lower you want to keep piston speed.

Re: What helps RPM's?
 

How did you figure gearing will help with RPM?????

Re: What helps RPM's?
 

Why do you want to rev the motor to 7-7.5k rpms? What are you looking to do?

Re: What helps RPM's?
 

I would like a 7-7,500 rpm limit for when i want to. I would not be at it all the time i just want an engine that can hit it.

Re: What helps RPM's?
 

stuff will live a lot longer at 6500rpm than it will at 7500 especially in a big block. you base your gearing on your engines operating rpm. unless your drag racing only theres no need to spin 7500rpm unless you want to spend a lot of money trying to find a combo that doesnt fly apart and constantly break stuff.

Re: What helps RPM's?
 

x2

Re: What helps RPM's?
 

Correct me if I'm wrong.....But...

If you have an engine built to make peak power at 7500RPM, but your gears are in the "high way" range, say under 3.00 : 1...Then why wouldn't you get lower gears to put the engine into its power band?


A........

Re: What helps RPM's?
 

I have 3.70:1 rear gears. I will be able to hit 6500 easy just would like to go a bit higher when i want. The rpm power is very nice i was just looking at how i could add a few revs.

Re: What helps RPM's?
 

Wrong.

You select the gearing based on what your power band is, transmission, tire size you have and what your goals are.

If I want an 1/8 mile car/truck and the power band is 4500 to 7k rpms then I could go with a really steep gear 5.XX:1. When I am going through the traps I want my engine to be at 7k+ rpms. Now if I want a 1/4 mile car/truck with the same engine/transmission/tire then I certainly can't run the same gear. I would need a lower gear. Either way the gear isn't going to affect what my power band is or how high my engine revs.

Re: What helps RPM's?
 

Diesel,

The premise of changing the gear based on the racing your are doing, is correct. IE the example above 1/8 might need a 5.30 gear. Same car 1/4 might need a 4.11. Same car, standing mile, you might need a 3.42 in that car.

The idea of tailoring your gear ratio to the style racing you are doing is correct. But, if a motor can only spin say 6k rpm, going from a 2.xx gear to a 4.xx gear, your motor is still only going to spin to 6k rpm..

Re: What helps RPM's?
 

Super73....

That was a great explanation of what you are all trying to say!

Things are a bit different with a sled hooked to you...LOL I understand exactly what you guys meant.



A.........

Re: What helps RPM's?
 

JUST GRAB THE SECOND STAGE AND YOU WILL SEE AL THE RPM'S U WANT :lol: GREAT INFO GUYS THIS IS THE MOST HELPFUL PEOPLE IN THE INTERNET WORLD. KEEP UP THE GOOD WORK.

Re: What helps RPM's?
 

I think ill stick with a 200 shot for a while. Never had juice and dont want to run wild with 2 stages right off the bat.. HAHA. Great looking set up you have there Bigboy.

Re: What helps RPM's?
 

dayum!!!!

Re: What helps RPM's?
 

my old combo was a 468 bbc iron headed 781 with port work,stock crank h beam rods, je pistons flat tap cam and i run 7000 rpm all day long. th400 3.73 gear 29.5/10.5/15 slick or street tires were 295/65r15 m/t et street.i forgot the 200 hp nos plate kit.that is what the shift light was set on. i ran the engine for 6 years and the only reason it broke was due to a faulty nos button (stuck) and before i got it shut down i got a piston. great combo i'll send you the cam specs. if you want.

Re: What helps RPM's?
 

Pm sent i hope that will help.