How to find TDC- Harmonic Balancer came loose from pully

I am not sure how it happened, but my harmonic balancer came loose from the pully. I can tap it towards the front of the engine and it will get tight again, but I am not sure how to line it up so that the timing mark on the balancer truely reflects TDC for piston #1 when it lines up with the mark on the timing cover. I had the engine apart down to removing the pistons and hand honing the walls (due to failed riser, but that's another post). The distributor was removed, and now I have no way of lining up the distributor to fire on the correct cylinder or set the timing. I think there is a way to pull off the valve covers and determine TDC by examining the movement of the rocker arms, but I am not sure? Anybody know?

Re: How to find TDC- Harmonic Balancer came loose from pully

Buy and install a new balancer is the best advice i can give you. The outter balancer part is liable to come right back off after running it a while.

Re: How to find TDC- Harmonic Balancer came loose from pully

I had the engine apart down to removing the pistons and hand honing the walls (due to failed riser, but that's another post).

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Ayuh,... 'n What motor might this be,..??

Re: How to find TDC- Harmonic Balancer came loose from pully

You mean the harmonic balancer came apart??? It is not going to work for the engine, so you will need a new one anyway. If you want to get an approximate indication of TDC you could hold your finger over the #1 plug hole to determine when it is on the compression stroke. If you have the timing chain exposed, there are some timing marks.

However, still guess work without knowing the engine . . .

Re: How to find TDC- Harmonic Balancer came loose from pully





I'm sorry it's a 4.3L vortec. I believe it's mercruiser's 4.3 LXH Gen + alpha. The harmonic balancer ( I think that's what it is) did not break, it simply seperated from the pully.It simply a steel ring. I thinks it's just pressed onto the pully. I think the pully must have a wedge shape to it, and as the harmonic balancer (ring shaped like a steel donut), gets pushed onto the pully it gets tighter. Hope this helps.

Kevin

Re: How to find TDC- Harmonic Balancer came loose from pully

Most balancers have the inner part which is bolted to the crank. This part also has your crank pulley bolted to it. Then th outter steel ring is pressed on with a rubber substance between the 2. Once they seporate they are garbage.

You can fight it or just buy a new one.

Re: How to find TDC- Harmonic Balancer came loose from pully

kpiazzisi said:

The harmonic balancer ( I think that's what it is) did not break, it simply seperated from the pully.

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It's broken.

The harmonic balancer is an assembly: center hub/rubber insert/outer ring. Once they slip or separate, it needs to be replaced.

Re: How to find TDC- Harmonic Balancer came loose from pully




OK...I get it now. I don't know how or when this happened. I pulled the motor to fix the transom, but when I pulled the motor the boat was running fine. The only reason I had to tear the motor down was because my F*** risers/manifolds failed while it was sitting idle in the garage for a year allowing rusty water into the back two cylinders. This baffles me how this could have come apart and the rubber that goes between the hub and ring is nowhere to be found. What causes this to happen? This seem like an unusual thing to wear out? They are going for about $60.00 used and $150.00 new. Should I steer clear of a used one? Also, can I use the same harmonic balancer that is used on a 5.7 L small block? Essentially they are the same motor as the 4.3L with two extra pistons?

Re: How to find TDC- Harmonic Balancer came loose from pully

Same thing happened on my corvette. I would shut the engine off and you could hear a jingle noise going on for about 10 seconds as that outer ring would keep spinning. I guess that rubber just dry rots or something. A good used one should be fine. That's what I replaced mine with. You really don't see this happen too often. This is the only one I've ever seen besides mine.

Re: How to find TDC- Harmonic Balancer came loose from pully

Used always is a quess!!!

Re: How to find TDC- Harmonic Balancer came loose from pully

That's an automotive part, easily bought from your local GM dealership or auto parts store. See if there are any numbers stamped on it and go from there. I checked flEbay and they were around $50 new, for an automotive 4.3L balancer.

Re: How to find TDC- Harmonic Balancer came loose from pully

There should be a bolt and washer that gets torqued down which holds the balancer to the threads in the front of the crank. I don't see that bolt in your picture?

Re: How to find TDC- Harmonic Balancer came loose from pully

Eric 3.7LX Alpha 1 said:

There should be a bolt and washer that gets torqued down which holds the balancer to the threads in the front of the crank. I don't see that bolt in your picture?

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He Probably removed the bolt. It has to come of, because it also holds the pulley on. I have seen them slide a little. But never come completely off.

Re: How to find TDC- Harmonic Balancer came loose from pully

Also, can I use the same harmonic balancer that is used on a 5.7 L small block? Essentially they are the same motor as the 4.3L with two extra pistons?

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Nope,... They're Not balanced the same...

Re: How to find TDC- Harmonic Balancer came loose from pully

I got one on the way and will arrive tomorrow at Advanced Auto for $44.00. The brand is " Dorman". I am not sure, but for that price it's probably made in China? The balancer has a key way, so I am assuming when I put the new one on, my TDC problem will be solved? Thanks for the help people, hopefully I can have this thing back on the water again. I have practically rebuilt the entire boat at this point.

Re: How to find TDC- Harmonic Balancer came loose from pully

Hey just an update. The balancer I purchased was different from the original. I asked for a balancer for a 1998 Chey Blazer since that vehicle also has the vortec 4.3L engine. The balancer however was almost 4 LBS lighter and a smaller diameter. From what I have researched I believe I need an older Chevy small block balancer pre 1996. The specs below are identical to the one I pulled off. The only possible difference might be the alignment of the timing mark on the outer ring. Sometimes the mark is 10 degrees off from the keyway. I think the 10 degrees offset is what I need. I am going to go down to Autozone tomorrow and check it out.

Type : Solid
Diameter : 6-3/4"
Width : 2-3/8"
Weight (lbs.) : 8.36
Make & OE# : GM 12551537
Brand : Dorman - OE Solutions

Re: How to find TDC- Harmonic Balancer came loose from pully

any numbers stamped on the old balancer...

Re: How to find TDC- Harmonic Balancer came loose from pully

kpiazzisi said:

Hey just an update. The balancer I purchased was different from the original. I asked for a balancer for a 1998 Chey Blazer since that vehicle also has the vortec 4.3L engine. The balancer however was almost 4 LBS lighter and a smaller diameter.

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Yes, you really need to reference the part number for the marine engine manufacturer (Mercruiser) rather than an automotive number. Mercruiser will have figured out the right balancer for the application. It may cost more, but getting the wrong thing from an automotive supplier is not cheap either.

I hope it all works out.

Re: How to find TDC- Harmonic Balancer came loose from pully

kpiazzisi said:

I believe I need an older Chevy small block balancer pre 1996. The specs below are identical to the one I pulled off.

Type : Solid
Diameter : 6-3/4"
Width : 2-3/8"
Weight (lbs.) : 8.36
Make & OE# : GM 12551537
Brand : Dorman - OE Solutions

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Could be, I found these specs for that balancer and it lists "V6 competition", a marine engine would fit into that category.

Part # 12551537
Harmonic balancer
Engine application: 1969-up 305 and 350; 90' V-6 competition
Outside diameter: 6.75
Technical Notes: Smaller size for limited clearance. Timing mark is 10 degrees before keyway centerline. Use with timing pointer P/N 3991435.

Re: How to find TDC- Harmonic Balancer came loose from pully

Interesting....The puzzle fits.

The # fishrdan provided is exactly the same as what I got. The only difference being that I got my number by finding a Dorman part with the same physical dimensions as the Mercruiser part. What threw me off a little was that the stated year for part 12551537 was pre 1996. I wasn't clever enough to look it up by a "1996 V-6 COMPETITION" which would have given me the same part number.

The Dorman part again is 594-012, It cost me $52.00 at Autozone and they had it in stock. The only difference I can see from the original is that I don't see the graduated marks on the ring that show BTDC and ATDC. They were very small marks on the original and I only found them after sanding the paint off. It's possible they are also on the Dorman hiding under the paint? To me this isn't a big deal. Each degree appears to be about an 1/8 on the balancer, so I can estimate if I want to tune to a few degress BTDC.

Yes the part is made in China, it's says so right on the box. I made a comment about this to the counter clerk and he said even if I paid more money for the GM part, there is no guarantee that's not made in China as well. Don't shoot the messenger, that's just what he said. Anyway, thanks for the help and I hope maybe someone else can use this post if they need help finding a balancer for a 1996 and newer v-6 Vortec marine engine.