70 340 Harmonic Balancer Slipped

I had some time in the garage so I wanted to confirm the TDC mark on my balancer so I made a piston stop (heads on engine). I lowered the stop and marked the balancer (CW and CCW rotations) to find that the OEM groove is not in the middle of my two new marks. I checked this twice and both times the OEM groove is not in the middle of the two marks. My guess is that the mid way of the new marks is about an inch off of where the groove is located.

What are my options?

Do I just make a new mark on the balancer in the middle of these two piston stop mark and use the ZERO that is on the timing cover?

Do I need a new balancer?

This is an OEM style balancer with the timing marks on the drivers side which I believe is correct for the 1970 340.

Thanks
Dave

It's now junk. Do not move the TDC mark. When the outer ring slips on the hub it no longer functions as a damper.

Buy a new damper and throw that one in the garbage.

If you have the wrong balancer, pre 70, the marks would be more like 90 degrees off not a half inch. So it's probably slipped on you.

Thanks for the replies. I will start looking for a new unit.

Dave

How bout either one of these?
https://www.norndaautomotive.com.au...odel=Small%20Block&series=V8%20340ci

When you remove the balancer to inspect it, check to see if it was installed with an offset key.

Have you also checked it for worn timing chain slop?

Not sure a sloppy timing chain would make any difference when verifying the TDC mark against a piston stop.

Yup.

It probably hasn’t properly functioned as a damper in a couple of decades.

Thanks everyone!

I got the bolt off of the balancer last night and then could not find my puller kit. But I will find it and get the unit off of there and inspect it. Once I inspect it , then I will measure the snout, then get another one on order.
I did not install an offset key the last time I had it off. This balancer has been on this engine during the 20 years that I have owned it. After reading some symptoms of a bad dampner, I have some clues that have been telling me that the dampner may be past it prime

Thank you again.

Question:
The new balancer/dampner that I have been looking at just have six tapped holes in the face, and a seventh one (quantities updated) that is located off of the main bolt pattern. My current OE unit has two squarish holes that I use to fixture it while I remove/torque on the middle bolt. How do you loosen/tighten the bolt on the newer units? Is that what the sixth hole is used as?

Thanks,
Dave

You use a balancer puller that uses the threaded holes.

Rebuilding is an option https://www.damperdoctor.com/

HOWEVER, I just had my '69 340 balancer restored by them and when I got it back I found they had not indexed it correctly. They apologized and will pay for shipping both ways. Looks like they do many many dampers, but was not impressed with their quality control processes.
Jim

This was so common with the '70 340's that it was standard shop practice to check TDC with a piston stop before attempting to time the engine.

And all OEM dampners have 6 bolts holding the lower pulley on, not 5

every dampner puller Ive owned uses 3 of those threaded holes to attach a puller to it to aid in removal

GTX,
I mistyped the 5 versus 6 holes, so I edited my earlier post. Thank you for the picture!


I am going to pickup a new puller on my way home from work today. I think I have the puller figured out now. Thank you everyone.

So now, how are you guys tightening down the 3/4" bolt to full torque without the crank rotating? I currently have all the plugs out and the pulleys off due to some other work that I was doing.

Thanks!

Dave

Setting the brake works for me and put the (manual) trans in high gear. If it doesn't have the tires or driveshaft in place, you can block the starter ring gear teeth.
This is one nice things about automatics: the park pawl simplifies everything.

I feed about 3 feet of 3/8"nylon rope down a spark plug hole in a cylinder that has the piston down near BDC. As the crank rotates it will jam the rope up against the head and stop it from turning, then you can torque the balancer bolt. Once torqued you can rotate the crank CCW to get the rope, since you have all the plugs out it should be fairly easy.

Some guys have a tool to hold the flexplate/flywheel but that's not necessary.

No worries about bending a valve with this method?

Never had it happen.

I got the balancer off and I did not see any issues, but I have already bought another unit (SFI) and it will be going on this weekend.



Thanks
Dave

Dave I might be full of it but it crossed my mind earlier that there might be an issue with how you did the TDC test & now that the balancer looks OK I feel compelled to humbly toss it out there

You may be right Robert. I was having trouble with my piston stop staying snug before I swapped this out, but I did not think that the mark would have been off by over an inch just because the stop was not staying snug.

I now have the new balancer on and the engine at TDC of #1 piston, the dist is pointing at the front, drivers side bolt like it should, #1 valves closed and the new balancer 0 is right in line with the stock 0 mark.
I am going to try that piston stop again and try to get it tighter in the hole.

Thanks Robert.

Torquing Balancer Bolt: I ended up making a bracket that bolts to the harmonic balancer and sets on top of the K frame to keep the crank from rotating while tightening the balancer bolt to the 135 ft/lbs. I can also use this same setup to loosen the bolt too in the future.

Thanks again to everyone.
Dave

How about a pic of that bracket you made.

All you need to loosen a balancer bolt is the right sized socket, a breaker bar and the starter.

Make sure you disable the ignition circuit, you do not want it to start up on you.

""How about a pic of that bracket you made.""

You may not be able to see them but there are spacers behind the aluminum bracket to fill the void in the new balancer. I just made it from material that I had laying around.

This is the tool that I used on my OE balancer a few times over the years. The bolt just goes into the rectangular hole and can be used to tighten or loosen the balancer bolt depending on what side it was moved too. But this one would not work on the new style balancer, so I just used the tapped holes as shown in the previous reply.

Dave

Just out of curiosity you might hold the old balancer up to the new one on the engine & clock the keyway slits the same & see if the TDC marks are the same. 10 degree off should be apparent

Robert.
I had them side by side on the bench before I installed the new one and they were very close.

Thanks
Dave