NBS's Necessary for 8k??
 

Along with other changes I plan to rev higher this season. I'm am installing valve springs to avoid the float. But, I've heard that GM recommends changing the balance shafts to neutral balance shafts for operation over 7500 RPM. Apparently because they are oddly weighted and spin twice engine speed they may explode when they see revs to high. Right now my motor is stock. I plan on building it after it blows, and I plan to install them then. It's kinda a pain in the dick to change them out with the motor in the car compared to out of the car. But, I would hate for the blown motor to be due to a balance shaft explosion.

So, I'm wondering who is running higher than 7500 with out them? And, does anyone know of a specific instance when they have failed.?

no reason to rev that high, make more power lower and save your engine

as for the float, the gm engineer told me years ago right when the stage kits were released that resonance happens at 6850rpm on the stock system, but GM wasn't concerned with it because it was such a small amount of time that the engine was from 6850-7000.

with a tvs, or some turbos there is.

There is reason to rev that high. Specifically avoiding a shift in the 1/4. With 26" tires in third @ 7400 my car will do about 118.5... too slow. 500 more RPM's would bring it to about 128 which would be perfect.

hey sorry i thought your post was NVS meaning new valve springs, not neutral balance shafts lol

whiskey is getting to me tonight haha

I know youve got a race car and know what youre talking about, but just a reminder, youre gonna get a shit ton of vibes.

the tvs makes peak power above 7200+ rpms and will hold it till 8k.

i run mine to 8k sometimes. not a lot. sustained 7500+ rpms will result in broken parts. one gear pull to 8k is not sustained.

anyone know what you torque the bolt that holds the gear to the shaft down to?

41 ft/lbs

Sustained as is running on the limiter?

Do you know of any that have broken specifically?

like area i rev the shit out of my car but only once in a while, mostly cause my turbo is far more efficient at the higher rpm range. in other words i get a lot of lag lol. on a serious note i use neutral balance shafts and the vibes aren't that bad. and its not that hard to pull the motor out.

A Tvs or converted to turbo lsj will make power over 7,000rpm to 8,000rpms if the tuning is there to back it up. I have a built motor and Iv been to 8k but I backed down to a 7,700 allowing me to hit 7,500 if I want to and not bounce off the limiter, only time I'll run 8k is dyno or track to save on my motor. There's really no need to on the street In My opinion, note I have my balance shafts deleted. Vibes are noticable. I would say do them, or get rid of them like I did it your call just concider them. It's better to be safe than sorry in my book. Just my .002 cents

make sure that gear sits flush against the end of the shaft with the bolt in there. you may have to shorten the bolt to get it set right.


i have had zero problems running to 8k every now and then. keep in mind, my car rarely see's anything above 10psi, or 4500 rpms on a daily basis. i hit 8k on the dyno, and the top of second at the drag strip.

normally i shift at 7600 when the overspeed light comes on.

I'm still undecided. The lack of specific examples of failure makes me want to think they can handle it. I'm only going to rev that high when I'm drag racing @ the top of third. But, that might be 150 times this year.

I'm leaning towards what I'm doing with the rest of the motor, beatin' it and hoping it doesn't break, and build when it does.

I've got the Bates bitchin' billet balance shafts, they are too pretty to grenade..