Balance Shaft - What is this?

What is this for???


sorry so small

That's so small I can't tell. Was it a cell phone pic or something? Is it in the LIM?

I'm guessing youre talking about the balance shaft?

It does what it sounds like it would. Balances the engines rotating mass more giving it less vibration. In a nutshell of course.

TonySmooth89 wrote:

I'm guessing you're talking about the balance shaft?

X2

Tony's right if that's what you are pointing at. It's a vibration reducer.

In the 3800 engine the balance shaft is an absloute necessity. Without it not only does it lope like a limping donkey but the engine shakes itself apart in relatviely short order.

If you search the web you should find a nice article about the balance shaft, why it's in there (it was not in the early 3800s) and how it makes the engine purr so nice at idle you can set a (pretty) full glass of water on the top w/o incident. To learn more specifically about the 3800 engine's inherent first-order imbalance, see:

http://engine.firebirdv6.com/3800history.html

and for more about engine balance shafts in general see:

http://en.wikipedia.org/wiki/Balance_shaft

Happy reasing,

Albertj

Actually, it's not completely necessary - If you 'upgrade' to a double-roller timing chain, you have to leave the balance shaft disconnected. I would never do this on a street car, I have driven a few and the vibration, although not horrible, is... pretty bad.

yea thats what I thought it was, again sorry about the size and thanks for the info

Completely necessary = no. Derek you're right - the engine willrun for some number of hours without one.

Desirable and useful = yes, even though it drags off some horsepower.

Albertj

By disabling the Balance Shaft, do you have to remove it completely?
If so, what does it involve. Are there plugs or something that go in it's place or is nothing necesary other than just removing it.
I understand if I want to change my Timing Chain to a heavier duty one, I have to remove the balance shaft and was wondering what's involved.

Rickw wrote:

By disabling the Balance Shaft, do you have to remove it completely?
If so, what does it involve. Are there plugs or something that go in it's place or is nothing necesary other than just removing it.
I understand if I want to change my Timing Chain to a heavier duty one, I have to remove the balance shaft and was wondering what's involved.

Mine was diabled prior to installation IIRC you have to remove the rear cover.. to disable it. not sure though..

rick, do a search on "disabling the balance shaft on a 3800 motor" and you will find lots of interesting info on how to. it sounds like a good mod with little consequence just a little more vibration. i like the idea but is a pia to do....

Thanks for the info.
I'll do some research and see if I want to do it along with doing the LIM gaskets and new L32 Lim and Gen 5 SC next spring.
Because I've already installed the 105# valve springs I'll be able to get a look at the timing chain and tensioner and see how much wear the springs caused if any. I'm curios after reading so many warnings about doing what I did.
I'll probably have about 5 - 6,000 miles, maybe more, on it with the new springs before i get to pull the timing cover. Will be a good experiment.
If there is heavy wear then I'd like to go with the double roller chain and new tensioner. Which will necessitate the removal of the balance shaft.
Then if your going that far in might as well do a mild cam also.
Ah, what the hell. This increase in Torque is addictive.

Quote :

I'll probably have about 5 - 6,000 miles, maybe more, on it with the new springs before i get to pull the timing cover. Will be a good experiment. If there is heavy wear then I'd like to go with the double roller chain and new tensioner. Which will necessitate the removal of the balance shaft.

I wouldn't think this is a long enough period to really see any significant wear to the tensioner. Did you you open the cover and inspect before you installed the 105# springs? If not, how do you know if the wear is attributed to the new springs or the OEMs?

FYI, with 150,000 miles on 90# springs and 1.9:1 rockers, I've never inspected the tensioner, but I expect to see some wear when I do (planned for 200k). So far, no reason to suspect the chain has much slack - engine still runs and idles very smooth.

does anybody here have the BS removed? and what do ya think?

AA wrote:

I wouldn't think this is a long enough period to really see any significant wear to the tensioner. Did you you open the cover and inspect before you installed the 105# springs? If not, how do you know if the wear is attributed to the new springs or the OEMs?
FYI, with 150,000 miles on 90# springs and 1.9:1 rockers, I've never inspected the tensioner, but I expect to see some wear when I do (planned for 200k). So far, no reason to suspect the chain has much slack - engine still runs and idles very smooth.

No, I did not do a pre-inspection. So this is not intended to by a highly scientific, value calculated exercise.
If you remember when I installed the springs, retainers and keepers there was a problem with the modified retainers hitting the modified 1.9:1 Rockers.
Unlike some other people, I noticed it immediately and put the OEM retainers back on while still using the 105# springs and new locks/keepers.
The Turtle was taking his apart at the same time due to valve train noise and he / we got to see the damage caused to the modified retainers by the 1.9 Rockers presumably because of using the ZZP Keepers. Because when he replaced those with OEM ones the clearance issue went away
After communicating with ZZP regarding this issue they told me by leaving the stock retainers in i was further preloading the already stought 105# springs by another .080" and that they felt leaving them in would cause eminent pre-mature failure of the Timing Chain Tensioner and additional stretching of the chain. (ZZP's words not mine) I chose to leave them in as there was no clearance problems and I was willing to take a gamble on the tensioner breaking, Zoomer warned me about this happening quickly.
The Turtle found he could use the Modified retainers if he switched back to the OEM valve keepers and not have any clearance issues and not have excessive pre-load on the springs and valve train.
So with all of the above said, I will be curious if I find excessive wear on my tensioner and chain. That's all. If I do, I will either put the oem retainers back in at that time and do some more deliberate measurements to see for myself if the OEM retainers actually do cause the additional .080" pre-load that ZZP says will happen. BTW, my idle is not so smooth anymore. Don't know if it's getting worse, I need a little more time to evaluate.
FWIW, I put clean, flow matched injectors in about 2 weeks prior to the rockers, didn't notice any rough idle at the time and have had the PCM tuned by Derek post Rocker arm/spring swap. So the slightly rough idle appeared after the rockers and springs and before tuning.
Based on the Stern Warnings from ZZP and from what I've read of other's experiences, I expect to find a badly worn tensioner and slack chain. That is if it makes it through the winter, I believe it will. But I am monitoring by the seat of my pants using my rough idle as a guide.

Oh, I see. Yes, I remember now. I agree, if you're noticing rough idle, maybe it's worth opening and checking out. If it's severely worn, I guess we could assume Zooomer was right. And then you could put in a double roller (removing balance shaft), or the simpler and less expensive route: 90# valve springs, which can be had for about $100. I have 4 extra (blue) if you can find 8 more.

Quote :

Which will necessitate the removal of the balance shaft.

I don't think it needs to be physically removed. It can be disconnected and left in place, or you could remove it. But it's there for a good reason, since V-6s are inherently unbalanced.

I'm going to monitor things based on idle smoothness or roughness, however you want to look at it.
Mainly because of the time of year, don't have the garage space and the idle isn't so bad that I am overly concerned. Not yet anyway.
I'm assuming it will be gradual wear and not catastrophic failure.
At least that's how I've experienced timing chain wear on your average, un-modified engine in the past.
IDK, anyone feel this should be tended to immediately.?

Rickw wrote:

IDK, anyone feel this should be tended to immediately.?

IMO, I believe that if there is enough of a symptom that it's noticable and you do believe it would be the timing set, it's probably bad enough to worry about. I wouldn't think the timing chain or dampener has a lot of room to get loosy goosy before it all-out fails. In other words, I'm not so sure it's going to give you the warning you're waiting for before it quits.

I sent an IM to Kemp about this. I'll get back with what he says.

Regarding installing 90# springs as part of the solution; if you compare the numbers on a chart of spring pressure throughout the full range of spring compression between the 90# and the 105# you find that the 105's have less pressure during initial and intermediate compression than the 90's.
The 90's aren't as progressive as the 105's. That is why i chose them over the 90's when I was researching what to buy.
It is only when you get to the higher end of the scale do the 105's exceed the 90's. Presumably to prevent valve float at high RPM's.
I never had intentions of setting my High RPM range that high to begin with, i have shift point's set at 5600RPM. The only real difference i could conclude is that the 105's could cause valve seat wear earlier due to closing pressures being higher upon valve to seat contact.

Thanks for communicating with Kemp on this. Another point of view from someone with much more experience on these engines is welcome.

For clarification on the above posts, I switched from compcams keepers and zzp modified retainers to a new set of the same compcams keepers and intense (LS1 style) retainers to fix my problem. I'm not sure if the keepers or the retainers or both were the original problem.

from what i understand ,removing the BS "improves engine reliablity"
it diverts less oil at high revs removes reciprocating weight and improves high end acceleration. from the searches ive done on the 3800 BS removal, the vote is that the vibration is not harmful to the engine and despite the odd firing order oh the 3800 this mod does not make the vibration "unbearable"....

Codith,
What I remember seeing in the pictures you posted showing the "old" (damaged) and the "new" (whatever they were) was increased valve stem exposure from the retainers, which in effect did exactly what my OEM Retainers are supposedly doing and that is compressing the spring more at rest and allowing the valve stem to be contacted by the rocker arm before the rocker arm contacts the retainer.
So when I saw those comparison pictures you posted i was much less worried and more inclined to disregard Zooomer's warning. Because you have ended up with the same picture as my end result. Obviously this all from a visual and without measuring in the right environment with the correct equipment.
Maybe you can find that snap shot showing your old vs new and post it here for review.

Quote :

Regarding installing 90# springs as part of the solution; if you compare the numbers on a chart of spring pressure throughout the full range of spring compression between the 90# and the 105# you find that the 105's have less pressure during initial and intermediate compression than the 90's.

I do understand, but the key factor is the 90# springs fit using GM valve retainers manufactured specifically for the 90# springs, so there is zero concern with them not fitting, or any clearance issues. As you've found, the same can't be said for the 105#s.

The numbers you are talking about are part of a theoretical argument that I believe was brought into light by ZZP in an attempt to steal some sales from INTENSE, who was pushing the 90# springs. 5 years ago, ZZP and INTENSE were in a bitter war regarding who was the best, and they both would often publish info disputing the other's findings. ZZP ripped on INTENSE's pulley groove design, and vice versa. INTENSE exposed the ZZP throttle body spacer as a potential coolant leak opportunity. ZZP claimed INTENSE Gen III rockers were junk, and there were other instances, including the debate over 90# vs. 105# valve springs.

Turns out every one of these claims was not due to a design flaw, or vendor incompetence, but instead most were either a result of improper installation by the consumer, or simply personal opinion. If you are a ClubGP(ZZP) fan, it is a fact that 105# > 90# springs, but for obvious reasons, I always take everything at ClubGP with a grain of salt.

The 105# vs. 90# argument seems to make sense, until you consider that it isn't known for certain how much spring pressure really causes premature wear on the valve train, seats, and chain tensioner. Sure, the more progressive 105# springs may have less pressure at initial compression, but no one has shown that the 90#'s initial pressure is actually harmful. Also, do you really need 105# of spring pressure at 6k RPM? I have revved that high many times with no problems. Many, many owners who installed the 90# springs kept them in and have enjoyed many thousands of trouble free miles. Others switched to the 105#s and gained some sense of security, but imho it really doesn't matter, or at least I haven't yet seen the absolute proof.

Imo, the real reason to use 90# springs is you can have proven, reliable daily driven operation (150k miles) + high RPM (6k) for track runs, and you need not worry about any clearance issues. The reasons for using 105# springs are valid in theory, but not actually required for long, trouble-free engine life, and you do need to be concerned with assembly issues, which ironically has been shown to cause a potentially catastrophic situation.