froggy47

I know the stock balancer has balance weights. If you replace stock for stock these weights must be duplicated on the replacement (stock) balancer per the FSM instructions.

Question is #1 does GM add the weights with the stock balancer ON THE MOTOR (in other words the whole rotating assembly is being balanced,
or

#2 does GM just balance the balancer after it's manufactured (off the motor)?

If it's #2, why would you duplicate the original weights?

I'm thinking it's #1.

vettehardt

The balancer will slip on the shaft during fast RPM changes. If you are not careful the bolt will back out and the balancer will slide off and hit the steering rack. Happened on my brother's 04. There is no key way or anything on the shaft to keep the balancer from spinning. It is just press fit onto the shaft. I know of at least 2 other people that this has happened to also. There is a guy in the Fort Wayne corvette club that has actually made a jig to drill a hole through the balancer and the end of the crank to drive a pin in it so the balancer will not slip. He did this to my brother's car and we haven't had an issue in 2 years now.

I don't know if they balance it on the motor or not, but it would seem counter productive if they know the balancer will slip on the shaft. So my guess is they balance it off of the motor.

froggy47

Thanks, anyone know about the questions posed?

davidfarmer

the engine is neutrally balanced, I'm not sure why they would add weights during assembly. I always key my cranks during a replacement thought, for reasons stated above.

froggy47

Thanks David, I'm not sure either, it's driving me a little nutty, but it's right there in the FSM. You match the same weights from the original (stock) balancer on the new replacement (stock) balancer.

Pumba

The engine is not neutral balanced by Chevrolet!

The entire engine assembly is final balanced while it is running and small weights are installed in the OEM balancer.

If you decide to remove the OEM balancer, you should replace it at the exact location from which it was removed. Before you remove the balancer, place a mark on the end of the crank and across from it on the end of the balancer so you can reintall it in the same location.

As others have stated, it is important to properly torque the OEM balancer when you reinstall it. Follow the instructions in the OEM Shop Manual.

froggy47

That's what I thought based on the FSM procedure.

So if you replace with an ATI, how does the ATI balance the motor???

Pumba

The ATI damper is neutral balanced. You will have a small amount of residual imbalance left after the installation of the ATI damper.

davidfarmer

that is interesting, GM Racing worked WITH ATI to come up with the proper viscosity joint in their balance, I guess that is to address the slight imbalance.

so when dealers replace the OEM balancers that fall off, I wonder how they are supposed to ever achieve proper balance????

froggy47

The procedure is (stock for stock) you scribe a mark before you pull the old one (timing cover & balancer - I guess - never did it), you line up the old/new (the new comes with holes but no weights).

The old/new do have a way to line them up based on holes.

You get a little kit of weights (they are different lengths).

You insert the new weights same as old. You measure how much hole is left to figure if you have a short/med/or tall weight.

You transfer the scribe mark old to new.

Line up the marks & press it on.

Having said all that, I bet maybe 1 in 50 tech's ever goes to all that trouble. On the average grocery getter nobody will ever know or notice.

moespeeds

My balancer just came off last weekend on track. Destroyed the P/S rack and I lost my PS on track. When I get this thing all apart I will pin the crank for sure.

froggy47

Was it the stock one? Did you get a "warning" noise or vibration?

Can you tell if the rubber "sandwich" separated or the bolt backed out or both?

It's a heavy piece, I can certainly see how it would hammer a rack to death pretty quick at high rpm.

Sorry to hear it.

moespeeds

Stock balancer, my p/s pump was whining, or I thought it was whining all morning, but I knew it was going anyway. Then out on track I tried to make a right and it was like I was suddenly driving a tractor trailer. The pulley actually milled it's way into the rack, yet somehow my serpentine belt stayed on despite running way crooked. When I get out to my trailer later I'll post a picture.

RX-Ben

Be careful with pinning these - you need to drill a radial hole (see, of course, the ATI crank pin drill fixture kit).
A well-known shop did an axial pin on my ATI damper (without my knowledge) and the balancer was nearly cracked in half when we took it off.
If I didn't lose two piston rings and I was able to actually compete in the last two events of last season, I probably would've lost the damper.

froggy47

My belt stayed on too, but only a couple of ribs wide. There's a video of mine on my YT channel (link below).

moespeeds

Hey Frog I have the pinning kit. I'll loan it to you if you get it back to me quick, as I'll need it in about 2 weeks. Just PM me your address and it will be on it's way. You can have the 2 pins that are in the kit if you get to ATI and order me 2 more.

froggy47

I have decided not to pin, assuming of course my crank measures within spec, I think it should. I will use the ARP bolt and red loctite as recommended by ATI. There is actually a technique to applying the loctite, I spoke with one of their engineers.

froggy47

I think the loctite red & arp @ 250 will do it, but I appreciate the offer, if I change my mind I'll pm.

Thanks dude.

Searya

For what it is worth I had an arp bolt back out on me. It too ate into my steering rack. The engine was rebuilt just 2 months earlier and the shop swears they used the loctite and proper torque. In either way they were great and fixed everything for free. But after reading this thread i am going to look into pinning the crank.

Question do I have to pull the engine to pin it?

froggy47

No, it can be done without pulling engine.

BTW the "Corvette Specialist" that put mine on said he did it all correctly, but I have my doubts. He did reuse the stock bolt for starters.