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70 340 Harmonic Balancer Slipped #2754644
03/22/20 05:08 PM
03/22/20 05:08 PM
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YO7_A66 Offline OP
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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


1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
Re: 70 340 Harmonic Balancer Slipped [Re: YO7_A66] #2754647
03/22/20 05:18 PM
03/22/20 05:18 PM
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Originally Posted by YO7_A66
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.


Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
Re: 70 340 Harmonic Balancer Slipped [Re: madscientist] #2754659
03/22/20 05:30 PM
03/22/20 05:30 PM
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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.

Re: 70 340 Harmonic Balancer Slipped [Re: Sniper] #2754714
03/22/20 07:19 PM
03/22/20 07:19 PM
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Thanks for the replies. I will start looking for a new unit.

Dave


1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
Re: 70 340 Harmonic Balancer Slipped [Re: YO7_A66] #2754998
03/23/20 12:44 PM
03/23/20 12:44 PM
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Stoney Creek, Ontario, Canada
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Re: 70 340 Harmonic Balancer Slipped [Re: YO7_A66] #2755055
03/23/20 02:54 PM
03/23/20 02:54 PM
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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?

Re: 70 340 Harmonic Balancer Slipped [Re: Alaskan_TA] #2755062
03/23/20 03:09 PM
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Not sure a sloppy timing chain would make any difference when verifying the TDC mark against a piston stop.

Re: 70 340 Harmonic Balancer Slipped [Re: madscientist] #2755124
03/23/20 05:22 PM
03/23/20 05:22 PM
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So. Burlington, Vt.
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Quote
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.


Yup.

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


68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
Re: 70 340 Harmonic Balancer Slipped [Re: fast68plymouth] #2755315
03/24/20 07:33 AM
03/24/20 07:33 AM
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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 up

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

Last edited by YO7_A66; 03/24/20 01:43 PM.

1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
Re: 70 340 Harmonic Balancer Slipped [Re: YO7_A66] #2755380
03/24/20 11:06 AM
03/24/20 11:06 AM
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You use a balancer puller that uses the threaded holes.

Last edited by NITROUSN; 03/24/20 11:07 AM.
Re: 70 340 Harmonic Balancer Slipped [Re: NITROUSN] #2755411
03/24/20 12:05 PM
03/24/20 12:05 PM
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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


1970 Superbird 440-6bbl, auto
1969 Barracuda 340-4bbl, FB Formula S auto
1969 Barracuda 6.1 L Hemi, 5 speed, Convertible
2022 Can Am Spyder RTL
Re: 70 340 Harmonic Balancer Slipped [Re: RealWing] #2755420
03/24/20 12:18 PM
03/24/20 12:18 PM
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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.


"We live in a time when intelligent people are being silenced so that stupid people won't be offended".
Re: 70 340 Harmonic Balancer Slipped [Re: YO7_A66] #2755422
03/24/20 12:21 PM
03/24/20 12:21 PM
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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

[Linked Image]

























Re: 70 340 Harmonic Balancer Slipped [Re: gtx6970] #2755451
03/24/20 01:37 PM
03/24/20 01:37 PM
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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

Last edited by YO7_A66; 03/24/20 01:44 PM.

1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
Re: 70 340 Harmonic Balancer Slipped [Re: YO7_A66] #2755462
03/24/20 02:26 PM
03/24/20 02:26 PM
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541 slobovia
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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.

Re: 70 340 Harmonic Balancer Slipped [Re: YO7_A66] #2755584
03/24/20 08:46 PM
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Originally Posted by YO7_A66
So now, how are you guys tightening down the 3/4" bolt to full torque without the crank rotating? I


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.

Re: 70 340 Harmonic Balancer Slipped [Re: Sniper] #2755604
03/24/20 09:29 PM
03/24/20 09:29 PM
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Originally Posted by Sniper
Originally Posted by YO7_A66
So now, how are you guys tightening down the 3/4" bolt to full torque without the crank rotating? I


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?

Re: 70 340 Harmonic Balancer Slipped [Re: BDW] #2755605
03/24/20 09:32 PM
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Never had it happen.

Re: 70 340 Harmonic Balancer Slipped [Re: YO7_A66] #2756523
03/27/20 03:54 PM
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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

IMG_6292.JPGIMG_6289.JPG
Last edited by YO7_A66; 03/28/20 08:53 AM.

1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
Re: 70 340 Harmonic Balancer Slipped [Re: YO7_A66] #2756796
03/28/20 10:49 AM
03/28/20 10:49 AM
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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


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