Since I was kinda jacking Cobalt Performance Part's thread, I figured I would make a new one here. I bought a set of neutral balance shafts along with a bunch of other goodies I'll be installing shortly. I bought them to allow me to rev the engine past 7k as GM recommends this to avoid severe lateral forces generated by counterweighted shafts.

Anyone install them on an Ecotec before? I'm pretty sure I can wedge them in there without removing the engine from the vehicle, but I guess I'll be finding out shortly. Feel free to discuss your thoughts on using them.

I'll post a pic of them in a sec... edit, or not, they're in the garage.

 

some people think the stocks shafts will hold a 8000 rev limit with no issues...

 

GM's Stage 3 installation manual was enough convincing for me to replace em. Not too bad of a price, 10 free hp, plus no worries about them destroying the engine. I'm replacing pistons, valve springs/retainers and cams as well, so I figured I might as well while I was at it.

 

can you get these shafts and leave the valvetrain in stock form just for the sake of freein up some ponies while maintining the 7000 redline?

 

Yeah, they aren't real easy to remove though, the timing cover has to come off and engine lowered slightly. I imagine you would also have to remove the timing chain, but I'm not sure about that, since mine will be off anyway.

 

some poeple are also wrong

 

^ i agree counter weight balance shafts are detrimental to non purpose built high reving engines.

 

Interesting discussion... I'll definately be watching progress.

 

you can slide them out on a jbody without removing the engine.

 

Yes, the timing chain has to come off. They are driven by the water pump chain, which is underneath the timing chain. There isn't enough clearance on the Cobalt to remove them without lowering the engine a bit.

Normally, this part is installed without issue while the engine is out of the car. Since they usually installed along with a number of other high-revving parts, it is odd to put them in with the engine still installed.

 

This is something i completely forgot about. Only problem is i cant change my Rev Limit yet. But i figure i might as well when i do my pistons/rods this month.

 

switching to neutral shafts also has the benefit of enjoying 10-15 more horses in stock form while you wait for your tuning to rev higher

 

I"m waiting for my head to get back before I assemble my new motor. but I will be using neutral balance shafts since I"ll be revving around 8k rpm til I go standalone and will be able to rev to 9k or so... should be fun..

 

Witt, I just got mine a few days ago. How high are you planning on reving?

 

Neutral shafts are really something I recommend doing only for a strip car. If you plan on modifying your car as a daily driver, leave the stock units. If you do get neutral shafts, you should also consider a solid upper engine mount.

Here's what you get with the neutral set. The ability to rev past 7000 RPM, and you free up 10 HP to the wheels.

Here's what you get with the stock set. The ability to rev to 7000 RPM, and a smooth running engine.

My build is a street car. I'll be able to make over 300 HP on pump gas without going over 6500 RPM. That's enough for me.

 

good post

 

are there any in betweens of neutral and stock balance shafts? so you can rev to say 8kRPMs and only have mild vibrations? ive never heard of this before, but it seemed like a good idea when i thought of it

 

The 300hp LSJ build book DOES NOT change the the balance shafts... it leaves the stock ones in. They made 300+ @ 8k rpm. Unless you plan on going over 8K rpm... you shouldn't NEED to change them. I pondered the idea for a while. A waste of $300 in a Daily Driver, if you ask me. there are a lot of much more needed things that $300 could go to.

 

x2 like a wideband

 

well if you're like me and have everything already..... it's the last thing I needed on my list... makes sense if your building a complete motor on the side (like me) for an extra 15 hp for $300 it's a damn good deal. and since once I go standalon I'll be up in the 8500+ rpm range... so it's a necessity

 

same here

 

On cars with them completely deleted, the only noticable vibrations are right around the 3-3.5K rpm range, its much less vibration then a polyurethane engine mount.
I'm not about to take the chance on a balance shaft ruining my engine. Most other GM publications recommend changing them at over 7k rpm, including the Stage 3 instructions.
I'm kinda beyond that point.

 

Before I upgraded my valve train I chatted with WopOnTour, about the Neutral balance shafts, he said it is a good idea, if your building a race only engine, no to much for an everyday driver.
we also said that there are numerous LSJ engines that they have built running at 9000RPM with the stock balance shafts.

the 300+HP book rev's there engine to 7800RPM and they don't replace the balance shafts.

so they are not required, but if you already have your engine out of your car, and you plan on making a race car/or just don't car about the increased Vibrations then enjoy the 10HP

 

[QUOTE=Witt;882113]
I'm not about to take the chance on a balance shaft ruining my engine. Most other GM publications recommend changing them at over 7k rpm, including the Stage 3 instructions.[QUOTE]

Yeah - go for it. If GM Engineers recommend something, there's usually a reason. Sure, you may be OK with the stock shaft but I think if you plan on running it up to 8K often you should get the neutral balance shaft to be safe. I think "someone" also said that you could run up to 7800RPM with the stock springs but I don't trust them either.

Really interested in seeing where this takes you, Witt.

Ian

 

[QUOTE=manticus;904574][QUOTE=Witt;882113]
I'm not about to take the chance on a balance shaft ruining my engine. Most other GM publications recommend changing them at over 7k rpm, including the Stage 3 instructions.i agree...you could make the argument that you can run the car to 280hp as well, but would you want to knowing the rods snapped at 281? of course not, you'd leave a margin of safety