Question on harmonic balancer

[spstan]

My understanding is when you replace the timing chain, you have to pull the harmonic balancer. Is it necessary to replace the harmonic balancer at around 80,00 miles? How do you tell if the balancer is bad? Can you re-manufacture a balancer (cause they're around $200 new).

Separately, the fellow (sorry don't remember his name) told me I needed a piston stop to replace the timing chain; my mechanic says no you don't. Whose right? Thanks for any advice. Paul

 

['66 Fury I]

Paul, I know the rubber in a balancer can slip, but I have never seen that. I have never needed to replace a balancer. That said, if you have doubts, check the TDC mark on the balancer against the actual TDC position of the #1 piston. That is when you would use the piston stop. If the engine is still assembled and has been running OK, I would remove the timing cover, roll the engine to align the timing marks on the old timing gears, remove the old gears and chain and install the new (without moving the cam or crank position) and close it up as per the FSM. Has always worked for me. Lindsay

 

[Big_John]

My understanding is when you replace the timing chain, you have to pull the harmonic balancer.

Correct

Is it necessary to replace the harmonic balancer at around 80,00 miles?

No

How do you tell if the balancer is bad?

If rubber looks shot or you think it has slipped. See below comment about TDC.

Can you re-manufacture a balancer (cause they're around $200 new).

Yes. In fact that ensures that you will have the correct balancer when done. Some later, external balanced engines require a specific balancer and it may be tough to get the correct one.

Separately, the fellow (sorry don't remember his name) told me I needed a piston stop to replace the timing chain; my mechanic says no you don't. Whose right?

No, just have to align the gear marks correctly, so it's better if the #1 piston is at TDC before you start to take it apart. You don't need a stop for that. Set the timing mark on the balancer at TDC on the compression stroke and when you pull the cover off, the marks on the existing gears should be straight up and down. If not, the balancer has probably slipped.

Find TDC by removing the #1 plug and placing your finger on the plug hole while you turn the big nut on the balancer. When it starts to blow out, you finish turning to the mark and there you go.

You will need a good harmonic balancer puller and an impact wrench to loosen the bolt. One of the $60 electric impacts at Harbor Freight should work to loosen the nut.

 

[spstan]

Correct

No

If rubber looks shot or you think it has slipped. See below comment about TDC.

Yes. In fact that ensures that you will have the correct balancer when done. Some later, external balanced engines require a specific balancer and it may be tough to get the correct one.

No, just have to align the gear marks correctly, so it's better if the #1 piston is at TDC before you start to take it apart. You don't need a stop for that. Set the timing mark on the balancer at TDC on the compression stroke and when you pull the cover off, the marks on the existing gears should be straight up and down. If not, the balancer has probably slipped.

Find TDC by removing the #1 plug and placing your finger on the plug hole while you turn the big nut on the balancer. When it starts to blow out, you finish turning to the mark and there you go.

You will need a good harmonic balancer puller and an impact wrench to loosen the bolt. One of the $60 electric impacts at Harbor Freight should work to loosen the nut.

Big ; instead of an electric impact wrench, can I use a breaker bar instead? Paul

 

[Big_John]

Big ; instead of an electric impact wrench, can I use a breaker bar instead? Paul

The problem with the breaker bar is the engine will tend to turn over as you loosen (or tighten). Some guys will say a piston stop will prevent that, but as I see it, that puts some unnecessary force on the top of the piston. It's not all that hard to break a cast aluminum piston or the piston land (area above the rings). The impact just unscrews it with no extra holding.

An electric impact is a nice piece to have. I broke down and bought one myself and use it a lot more than I thought for small jobs. I would have used my pneumatic impact before for a harmonic balancer... Also great for changing tires, working on exhaust etc. You might be able to rent one too.

And before someone says anything, I used my 3/8 HF impact to loosen the pinion nut on my 8 3/4 rear the other day...

 

[CBODY67]

Piston stop to keep an engine from turning? What a concept! That's TWO uses for that item? NOT!!! The ONLY time you use a "piston stop" is to verify TDC with the cyl heads removed. I recently saw a video of a "TDC whistle" that goes in place of the #1 spark plug. As you roll the engine over with a breaker bar, as the piston moves upward on compression, the whistle does its thing. Just have to do it slowly so when the whistle stops suddenly, that's TDC. FWIW

Main thing on harmonic balancers is to NOT remove them with a pulley puller with jaws which pull on the outer ring of the balancer. A sure way to separate the two parts!

From what I've seen, as noted by my late machine shop operative, when the outer ring on a balancer moves, it does not always rotate (as suspected), but moves rearward on the center hub, with the rubber interface being pushed forward at the same time. Easy to see this, too. Seems like there is a damper rebuilder I've seen an ad for, somewhere?

IF you get into the drag race engine realm of things, there are many expensive dampers that are out there. Summit, Jegs, or similar sells them.

The accuracy of the marks on the damper are related to the accuracy with which the keyway groove in the crankshaft nose was machined. With #1 cyl at TDC, the keyway should be pointing to the centerline of the piston pin of #1 piston, which can be visualized on the front of the block, if you know what you are looking at. Verifying #1 at TDC is where the piston stop or piston whistle comes in.

In the case of an engine which just does not run correctly at something similar to normal base timing, the accuracy of the keyway slot machining might well be the issue. I heard of one cases, from my late machine shop operative, of a race engine which needed something like 60 degrees BTDC to run as it should. A different crankshaft put things back to where they should have been.

Take care,
CBODY67

 

[Barry S]

When I replaced the timing chain on the Newport, I was able to remove the Harmonic Balancer nut with my battery impact wrench, it worked great.

The challenge was tightening the nut to spec when I was putting things back together. Here's how I solved it - I took a piece of scrap 3/4" plywood and drilled it to mount to the front of the harmonic balancer using the bolt holes for the pulley. That held it in place while I tightened the nut with my torque wrench. That also worked great.