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40 posts on a harmonic balancer? I'm going to make it easy. You're planning to remove the engine in the fall for rebuild, right, so reinstalled the old balancer and timing it by ear and call it a day for now. Return the new balancer because I don't think it's the correct one either from looking at the keyway. I've stopped buying parts from RockAuto. Too many times I've gotten the wrong part placed in the wrong box from them
I got the harmonic balancer out pretty easy using my puller and a crow bar as backup on two of the bolts. Once it popped I switched to a ratchet and it came right off.
The new one is a different design than the one I took off but looks to have the same mass. You can see in this photo the timing slot is in a different place relative to the key slot so I assume the old one has slipped. You can also see the old one has a pretty worn seal area. Right this minute I just want to put the new one in and get the C3 running and worry about the seal this winter when I plan on pulling the engine and rebuilding it.
In this shot the key slot is at 12 o'clock on both hubs and the timing slot on the old one is way off to the right.
From the top the hub looks the same...
JT
He has the right damper. His timing cover matches it.
Grumpy's Garage says the 82s balancers have a timing mark on the balancer that is 10* to the passenger side of the keyway and balancer bolt line. The blue line in the pic below.
The picture that stingray posted confirms that on his.
The OPs 2 balancers are below.
The original one, on the right side above, with the red line, is ~30-40* off of the keyway "center" so it appears to have slipped.
The replacement, on the left above, may have the correct spacing, but a straight-on angle would more easily confirm that.
Not necessarily slipped. It could have come that way.
One can not jump to conclusions without accurate information and comparisions. (don't compare to something from RockAuto)
If I could find that old post about someone asking about balancers.
That post had an excellent photo of two balancers, both were new.
And a legitament question from a poster why they were different.
One had the keyway lined up perfectly with the TDC indentation.
The other had the keyway offset of the TDC indentation.
Different years, different designs was the assumpsion.
So, inconclusion, will the O.P. new balancer fit? Of course. Will it work? Only if timing tape is attached because the TDC mark is way off.
And here is a little tip BEFORE installing any harmonic balancer.
Place it face-down on a work bench. Using an electric scribing tool, put a reference mark across both the outer ring and the inner ring. (If you do not have a scriber, use a dull chisel)
Then in the future, you will have a refence mark to prove the balancer did or did not slip.
Last edited by HeadsU.P.; Apr 17, 2025 at 08:24 PM.
There have been some good recommendations here about replacing a harmonic balancer and doing it on the car. I realize the OP already has a plan moving forward but other people will see this thread in the future and learn from it. So, I'll add this.....
The problem with online parts finders on vendor websites is they tend to only find a part that the vendor says fits which may not fit the application, doesn't fit the application at all, or will fit "good enough". But what did the engineers specify fits the application? That's where the Chevrolet Parts Catalog comes into play. Always find part numbers from the Parts Catalog then use that number to cross reference to parts that are available for purchase. Working the other direction can work but it is full of potential failures. Like getting a part that's thicker or thinner potentially causing interference problems or whatever.
Here is a screen shot of the Chevrolet Corvette Parts Catalog covering 1953-1982 model years. Note the part number for a 1982 and compare it to the part number you have been using. GM made millions of small block V8s and there are different balancers/torsional dampers for different applications not just simply 7" or 8" varieties.
Look on the back of the original balancer and there should be a 4 digit stamped (not cast) number in it typically on the flat of the keyway spoke. What does it read?
According to the GM Parts Giant Part Number: 12551537 Replaces: 6272221.
The old harmonic balancer has 8653 near the outer edge then near the key slot A 8 F
If the OP has this timing cover, he should be fine. A later cover from a different application might have the timing mark at about 12:00 but this would be typical for the C3.
Timing chain cover looks the same as your but a lot dirtier
JT
Grumpy's Garage says the 82s balancers have a timing mark on the balancer that is 10* to the passenger side of the keyway and balancer bolt line. The blue line in the pic below.
The picture that stingray posted confirms that on his.
The original one, on the right side above, with the red line, is ~30-40* off of the keyway "center" so it appears to have slipped.
The replacement, on the left above, may have the correct spacing, but a straight-on angle would more easily confirm that.
The old one is about 43°
The new one is probably 10° but it's hard to get an accurate measurement without a half shaft with a key to make sure the base of the angle gauge is on center and parallel to the key slot.
JT
Installing the harmonic balancer is pretty straight forward but I thought I'd just cover the steps I used.
I measured the depth of the hole and the stick out of the crankshaft nose and got a distance of pretty close to 1" within a few thousands. So this is the measurement that after installing the harmonic balancer the nose of the crankshaft should be recessed into the harmonic balancer.
I assembled the adapter (in my case 7/16"-20) onto the tool and snugged up the center bolt so when unscrewing the tool the adapter comes out with the tool and is not left in the crankshaft.
In the car I had to slide the harmonic balancer onto the tool then screw it into the crankshaft. I installed the bearing and big nut and ran them up by hand. Then rocking the harmonic balancer back and forth I "found" the woodruff key and got the slot lined up. The harmonic balancer went on about 1/4" or so at that point so I knew I had it lined up correctly.
I used a large adjustable wrench as a backup on the tool and let it rest on the water pump. Then just tighten the large nut until the harmonic balancer has seated against the shoulder on the crankshaft. I removed the tool and measured the depth to verify it was fully on.
Next I found it impossible to start with one hand one of the short bolts that holds the two pulleys on so I found some 3/8" fine thread bolts and cut the heads off. I put the two pulleys on and then installed the center bolt and left it a tad loose. The short bolts were easy to start after that.
You have the correct balancer. ~10* is correct for your year and you have the matching timing cover.
Your only balancer choices are 0*, 10* and 30* for different years, 10* for 70 & up C3s. Not 68s, they were 0*. 69 could have been either 0* or 10*, if early or late.
43* is definately slipped. The rubber part does not look totally intact, and I thought you had posted a picture where it had moved "proud" of the hub, in or out.
Personally, I would always get a $9 piston stop screw tool, and check the piston/balancer/tab timing relationship.
Anytime the balancer is removed.
Correct timing is that important!
This is all you need, and some masking tape. A ruler, and a sharpie.
No degree wheel required.
Rotate engine by hand slowly until timing mark looks around ~30* of tab zero or so. Tighten piston stop. Bump into it once or twice. Put masking tape on balancer there. Mark tab zero location on the tape with a sharpie. Needs to be 2-3 " away from balancer line at this point. Exact distance or degrees is irrelevant.
Then do not touch piston stop, and rotate engine in reverse, by hand, until the same mark is close to 3" on the other side of tab zero. Then rotate engine very slowly until it bumps into the piston stop again. Mark tape there with sharpie.
There should be ~ 4-6" between sharpie marks. Exactly half-way between them is true piston TDC. Measure this and make a new sharpie mark at half-way.
This third mark should, but may, or may not, match the scribed line on your balancer.
You may need to correct the balancer with permanent degree tape if it is off. Or many racers grind the timing tab to a point, in the exact correct position. On a race engine they want it within 1* of exact, or even less. That is why the fancy adjustable pointers exist.
Personally I would do this on any engine any time the balancer or timing is replaced. Always and without fail when parts are replaced.
Stuff happens, and this relationship is that important.
@leigh1322 Thanks for the information. Everyone has their favorite way to get from start to finish and I do appreciate hearing about all the methods.
I do feel as a machinist among other trades that my method of finding TDC is as accurate or even more accurate as the stop screw method. The reason I feel this way is due to the multiplication factor of having a short feeler inside touching the piston and 7 time more outside. I can feel a small change like 0.001" in the piston which is 0.007" movement where I'm holding the "stick". Even a move as small as 0.010" in piston travel will show up as 0.70" movement in the end of the "stick" which is a huge amount to "feel".
I am glad to report that the line on the harmonic balancer lines up perfectly with the 0° mark on the timing cover timing tab when the #1 piston is at the top of it's travel on the compression stroke.
I fixed the distributor timing so the rotor points to #1 when #1 cylinder is at TDC on the compression stroke, put new plugs and plug wires in and it wouldn't start... until I plugged in the distributor then it fired right up and sounded better than it ever has. I set the timing after it warmed up and throttle response is great and idle is great.
Just need to put the seat and hood back on and see if changing the control valve affected the steering wheel position when driving straight ahead.
So just to recap in case someone happens along...
The original part number for the 82 harmonic balancer is 6272221 and it was replaced by 12551537. Thanks to @70s for posting the chart. Both the original and the replacement have the same weight even though the shape of the outer part is different.
