Internal or External Balanced Harmonic Damper?

[NeionDeion]

If someone could please help, I pulled this harmonic damper this morning to replace it, I am not sure if I need to buy an internal or external balanced damper? I am working on a 1972 Plymouth Scamp. The vehicle originally came with a 318, it now has a 360. If I did my research correctly the 360 engine is from 1976. I read in one of the forums that all 360's are external balanced. I do not know anything about the original engine build. I don't want to put on the incorrect balancer and damage the engine.. I have a 727 three speed automatic transmission, not sure if that info matters. Any help would be great.

 

[brian6pac]

Looks like it has been re-balanced with a internal balance balancer.

You probably need to keep that balancer on it.

 

[Locomotion]

Yea, It looks like someone tried to duplicate an externally a 360 balancer using a neutral balancer. Notice that weight is taken out on the keyway side also.

Pic is of a later model 360 where the factory removed weight. The original 360 version had a counterweight cast into it opposite of the keyway. I guess it as a manufacturing and material cost saving measure to take weight out instead of adding it. (Kinda like B&M did with their externally balanced flexplates.)

If everything internally is OEM and not lightened, an OEM 360 (non-Magnum) balancer should work. But you don't know if anything was changed inside.

 

[oldkimmer]

Well I can say I’ve never seen it done that way. If it was good b4 I would put it back on. Was it shaking or vibrating the motor? Kim

 

[pishta]

man that thing is cobbled... But if it worked, Mopower to ya! All 360's are externally balanced from the factory. And stock 360 dampers are not hard to find.

 

[oldkimmer]

That is an internal balanced damper that was externally balanced. Kim

 

[NeionDeion]

Well I can say I’ve never seen it done that way. If it was good b4 I would put it back on. Was it shaking or vibrating the motor? Kim

It wasn't vibrating, I had a coolant leak coming from the timing chain cover. I ordered a new and correct timing chain cover, the one that was on the engine was a 273 one with the extra bolt hole and no timing marks. I figured I should change the balancer since it's already off?

 

[NeionDeion]

I ordered a new balancer from Summit Racing, but after reading some of your opinions I'm not sure I should change it? the one I ordered from Summit has a removable weight, apparently it can be configured either way

 

[oldkimmer]

It wasn't vibrating, I had a coolant leak coming from the timing chain cover. I ordered a new and correct timing chain cover, the one that was on the engine was a 273 one with the extra bolt hole and no timing marks. I figured I should change the balancer since it's already off?

That’s a good plan to change it but u don’t really know what they did if anything to the motor. U can mark the old damper the same as a new one or change the damper that’s for a 360 and hope for the best. If it doesn’t vibrate with the new one ur probably good to go. If it vibrates u will have to put the old one back on. That one should work for u. Bolt the weight on it. Kim

 

[cudamark]

If it didn't vibrate before, I'd bolt the old one back on. Anything else, and you're asking for a vibration on a non-stock setup like that.

 

[NeionDeion]

man that thing is cobbled... But if it worked, Mopower to ya! All 360's are externally balanced from the factory. And stock 360 dampers are not hard to find.

If it didn't vibrate before, I'd bolt the old one back on. Anything else, and you're asking for a vibration on a non-stock setup like that.

Thanks cudamark. It's going to pain me to put that thing back on. I bought a new timing chain cover, fuel pump, water pump, power steering pump, alternator, and pully's.

 

[pishta]

There may be 2 weights: be sure to use the LA and not the magnum weight, they are different if you go that route. And to say the motors were balanced at the assembly line is not quite accurate on the neutral balanced motors. Everything was neutral balanced so they just stacked up a bunch of zeros to get a bigger zero (out of balance) on the 273-318 and the forged 340 motor. The cast motors had to have an extra weight on the balancer to make up for the lighter cast crank material. It was a general weight offset, not run on a balancer or anything. Production balance was pretty good but not even close to a "balanced" motor.

 

[OLDSTYLE]

Looks like the balancer in picture was custom balanced to the rotating assembly. Not pretty but to replace it you should rebalance the whole rotating assembly.

 

[NeionDeion]

Looks like the balancer in picture was custom balanced to the rotating assembly. Not pretty but to replace it you should rebalance the whole rotating assembly.

Thanks, I appreciate the advise. I wanted to throw that thing in the trash, looks like I'm stuck with it