1968 340 harmonic balancer and main pulley

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Tobor

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Can anyone help me figure out what I need to replace/upgrade a seemingly janky/wobbling harmonic balancer and main pulley?

I have a 1970 340 TA 6 pack motor in my 1968 Dodge Dart GT. I believe when I had the motor installed, the old harmonic balancer and pulley was used. It wobbled in the pre ious 1973 360 motor that was in the car when I bought it.

I know there is a inherent problem be ause the timing marks are on the passenger side and I believe part of the timing housing on the 1968?
 
360 balancers are specific to 360's only. They are for external engine balance. The 340's are internally balanced up to 72 or so. You need the correct 340 balancer for a 273, 318, 340. Don't run the engine with that balancer on.
 
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Sorry for the misinformation.
Whatever, I have on this set up, I’ve been running for 2 years. So, it must be an internally balanced harmonic balancer. However, the last two mechanics that have worked on car were pointing out that something must be bent or something, recommending that is should be replaced.

It does wobble and does not look smooth and straight as other period cars I see.
 
You need a balancer for a 340. then. I would replace the balancer first. The pulley might be ok. You could start a wanted ad for one. I would look around for a new one. Many of the old used ones aren't in any better shape than the 45+ year old one you have. Here's only one place that has many choices. 1970 Dodge Challenger Parts | Balancer | Classic Industries
 
As said above, the wobble can be just due to the age of the damper/balancer. There is a thin rubber between the inner hub and the outer ring of the damper that gets old hard, rotten, and cracked. It could allow the ring to slip out of alignment. Being this old, it is well past due for replacement anyway. Once the rubber gets hard, it does not do its job right anymore, and if the rubber is cracked, it is even worse. And if the rings flies off due to the rubber failing, then all he** can break loose.

As TMM says above, the 360 balancer is not to be used on the early or late 340's. You need to have the right one to avoid excess bearing wear, and other possible problems. Just because it has been in there for 2 years does not mean it is right.

If this is a 360 balancer, it will look imbalanced. It would look like in this thread:
  • Harmonic Balancer questions
  • or have a wide groove machined partway around the outer ring on the front or back
  • or have a weight connected on the back side (for some aftermarket parts.
  • And the late 340 balancer is also imbalanced but if it is a factory late 340 balancer, it supposedly will have the words "for 340 only" stamped on it
But, we need to ask another question: Was this engine rebuilt, and if so, was the engine re-balanced, and if it was re-balanced, was this damper provided to the machine shop for the re-balance process?

If the 340 was installed, and the old 360 damper just put on to complete the installation, then it is 99% probable to be wrong.

And yes, the pre-1970 timing marks were on the passenger side of the timing cover. 360 damper marks would be set up for the cover's timing marks to be on the driver's side.

Of course, now we need to ask the questions about the flexplate and torque converter, of whether they came with the old 360 motor? The same 340 to 360 balance differences existed at the back end of the engine.

Sorry to be so confusing.....
 
You should also know that not all 340's were internal balance. The good thing is the external balance 340 balancer says right on it "use with 340 cast crank only". 72 & 73 340 were external balance. May have been some early 72 that were internal.
 
You should also know that not all 340's were internal balance. The good thing is the external balance 340 balancer says right on it "use with 340 cast crank only". 72 & 73 340 were external balance. May have been some early 72 that were internal.
Good point. less cam, smaller valve heads and external balance. Horsepower was on it's way out. Emissions was in.
 
So many little details. You could write a book on one year model change.
 
Thanks for all the information and input.
Anything is possible, but I am doubting anything is terribly mismatched i.e., having the old engine’s (360), harmonic in this set up. I bought the engine from a very reputable business owner/friend and high end Mopar guy that I’ve known for over 30 years. He told me the engine was rebuilt to factory specs by Ronnie Keselowski, former NASCAR driver/mechanic from Auburn Hills, MI.
I looked at the photo of motor when I bought it (3-4 years ago) and it had a harmonic balancer and main pulley on it.
I have had several real reputable mechanics work on my car and none ever mentioned anything as drastic as a wrong harmonic balancer. The last one said I should get a new harming balancer and pulley to smooth things out.

I just want to make sure I am buying the right parts and all because of the differences I had to deal with in putting a 1970 340 TA 6 pack motor into a 68 Dodge Dart.
 
DECBD9ED-9FBD-423F-865C-B45536165935.jpeg


Just after install about 3 or 4 years ago.
 
Thanks for all the information and input.
Anything is possible, but I am doubting anything is terribly mismatched i.e., having the old engine’s (360), harmonic in this set up. I bought the engine from a very reputable business owner/friend and high end Mopar guy that I’ve known for over 30 years. He told me the engine was rebuilt to factory specs by Ronnie Keselowski, former NASCAR driver/mechanic from Auburn Hills, MI.
I looked at the photo of motor when I bought it (3-4 years ago) and it had a harmonic balancer and main pulley on it.
I have had several real reputable mechanics work on my car and none ever mentioned anything as drastic as a wrong harmonic balancer. The last one said I should get a new harming balancer and pulley to smooth things out.

I just want to make sure I am buying the right parts and all because of the differences I had to deal with in putting a 1970 340 TA 6 pack motor into a 68 Dodge Dart.
Good deal. We wanted to cover all the bases with you, so as to know what to look for, and some wrong combinations do show up from time to time. If the existing damper is pulled, then you'll know what to look for; with a '70 340, there should be no obvious imbalance to the damper ring.
 
Well why ask questions here when all your mechanic friends have all the answers?
:poke:
Well, no they don’t have all the answers. I try to stay engaged in the process with both eyes open, even though I can’t do the work myself. I’ve been skunked by a couple of wanna be mechanics that have caused set backs and costly redos. People do make mistakes and I try not to waste money and time.

I am sure you can appreciate that unless you have the expertise and skills to do this stuff yourself, it is harder and harder to find knowledgeable, trustworthy mechanics who know how to work on theses old gems. Hate to say it, A dying breed of masters!
 
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Not related to pulleys, wonder what happened to the car that engine came out of?
 
Good deal. We wanted to cover all the bases with you, so as to know what to look for, and some wrong combinations do show up from time to time. If the existing damper is pulled, then you'll know what to look for; with a '70 340, there should be no obvious imbalance to the damper ring.
Thanks.
Not related to pulleys, wonder what happened to the car that engine came out of?
Yup, I don’t know. I will ask the guy who sold it to me. But, you wonder? Car accident, someone deciding they want an “upgrade”........ I know there are guys out there looking for their orphaned engines. Needle in a haystack.
 
I got a neutral balance one for $10 in the for sale ads. Internal balanced and the ring marks match up with new one. Even internal 'neutral' balance dampers may have a divot out of them to balance themselves out. 360 dampers have a huge imbalance on the damper, they almost look like eggs, cast 340 ones too.
 
I have a 340 main pulley, two belt, if you need it. Just PM or txt me your address and I'll send her off. Free. Peter 7345453794
 
It's the season of giving. If you need my balancer too, drop me an address in the PM. You'll be me and Peters not so secret Santa recipient.
 
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