Straight from Bill Duncan:

"Balance shafts are good to 7500 rpm"

"At 7000 rpm the production balance shafts are taking 15 to 20 hp to turn. The neutral balance shafts take less than 1/2 that".

"It is what is called rotating inertia. Think of that as the energy to get the object rotating and keep it rotating. A symetrical shape takes much less energy to make it spin and to keep it spinning".

"Also areo dynamics comes into play. A production shaft is basically 1/2 a cylinder (off set weight from center) it has to push the air out of the way each time it rotates. A Neutral balance shaft is a complete cylinder and does not have to move any air out of the way to make it rotate. The balance shafts rotate at twice engine speed so at 12,000 rpm balance shaft speed that is a huge amount of air to push out of the way".

"Also friction is a factor a production balance shaft with it's off set weight has a huge side force in it's bearings causing a higher coeffecient of friction which means it takes more power to make them spin".

Bill explains it in more of a physics/engineering aspect (so some might not totally get it), but it covers everything you really need to know in order to understand the role neutral/balanced shafts play.

 

i under stand the reason for them but IMO it just a comfort thing just like the slincer holes in the SC or am i totally wrong

 

Comfort thing??

Plugging the blowers silencer holes is a nonsense mod for sound.

Installing NB shafts is something that is actually useful especially if you have cams, and are using the upper rpm range for racing, and such.

I dont think u fully understand the reason for them judging by your response to my post. I'm not knocking you by any means, but def go back and read the information I posted from Bill Duncan.

 

but why would you need them at all really

 

If you are going to run the stock valvetrain, and not build up the head, engine, or rev high you wont ever need them.

If you plan on getting the most out of the engine, and building it up right they can be a useful mod. Again, you dont really need them unless you plan on reving past 7500rpm. They do free up some horsepower that is other wise used to spin the balanced shafts though.

 

ok thats what i was getting at i plan on building the head but was not plaing reving over 75k cause i thought it was found there was no power gain over 7k or am i wrong again

 

On stock cams, no there is really no power gain over 7000rpm. Unless, you are running something other than the M62.

If you check out the LSJ build book you will see the engine they dyno at the end of Chapter 6 continued to make power after 7500rpm. That engine was running GMR cams though.

 

got ya well thanks for info still unsure bout getting cams i do take the car on long trips sometimes and don't wont to worry bout drivabltiy but if i do get cams i'm looking at ZZP stage 2's

 

No prob man.

 

i found that, but i didnt see the dyno chart from it in the book, and it even says at the bottom of the page to look for the chart for the build results

 

cool deal thanks

 

Hahah, yeah the build book has some errors in it.

I love when they show the pulley at the end of Chapter 6, and say this is the GMS3 pulley when it's clearly stamped 77.9mm, haha.

I also have an older PDF version of the build book, and they use a 73mm pulley for testing.

 

taking advice from a glorified PR guy is the last thing i would do.

 

Well what would u suggest

 

Area, whats your problem with Bill?

You have said this once before about him. Just wondering.

 

because it's true.

 

keep the meth tune you have n do a small nitrous shot you will get way more out of it and with less headaches. what I did and glad I didnt do cams.

 

i run ZZP stg 3 cams, but i also consistantly rev to 8000+ stock lash adjusters. Supertech valvetrain. dont go with anything more than stg2s if u wanna streetable ride. the 3s are pretty wild and they raise the powerband way up in the RPM range. they make power past 9500 rpms so i really cant even fully take advantage of them... YET.