Do I have the correct harmonic balancer?

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36DodgeD2

36DodgeD2
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I am in the process of changing the cam in my 70 Dart. It has a 78 la 360 and I know it is externally balanced. The balancer has a smooth face and I have seen a video that shows a balancer with a half moon relief in the face. I have noticed that there is slight vibration at or above 70 mph. The car has a four speed with the correct externally balanced flywheel. Do I need a different balancer?
 
Was the engine ever rebuilt with new pistons. I just had a 360 that was rebuilt, Was neutral balanced and the 360 flywheel through the balance out. There could be a reason for the neutral Damper.
 
Oldmanmopar said:
Was the engine ever rebuilt with new pistons. I just had a 360 that was rebuilt, Was neutral balanced and the 360 flywheel through the balance out. There could be a reason for the neutral Damper.
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The engine has been in the car for about 15 years. I have had it for about 10. It always had a vibration at high mph. It had a 904 auto trans which I changed to an 833 four speed four years ago. I did have a professional built driveshaft put in which solved a lot of the vibration problems. Just not sure about the harmonic balancer.
 
The engine has been in the car for about 15 years and I have had it for about 10 years. It had a 904 auto trans which I changed to a 833 four speed about four years ago. I installed a professionally built drive shaft that cured most of the vibration problems. Just not sure about the balancer after watching the video with the balancer with the relief on the face.
 
Was it ever rebuilt? Why I ask is we just had one here on a run stand. It was a 360 with the externally balanced damper. We assumed it was externally balanced so we put a 360 flywheel on the motor to fire it. It vibrated at a higher RPM.

So we installed a neutral balance 340 flywheel and the vibration was gone. What we found was the motor was rebuilt and neutral balanced and they left the 360 damper on it when balancing it. Just something you may want to consider.
Inspectung the crank in the engine my son found a heavy mallory metal slug in the rear counterweight of the crank. Nothing in the front of the crank because they kept the 360 damper on it

Your motor having the neutral damper may habe neen neutral balanced years ago an that is why they used a neutral damper. Could be the flywheel that is out. The damper being out wouldn't give a vibration you would feel in the car with rubber mounts. The flywheel will
 
Member 1969383valiant has a neutral balanced 400 here at the shop in the crate right from chrysler. Warrantee engine. Warranty engines were built for replacements for early cars when the original were no longer available. The 400 that is here is a replacement for a 1971 383 4spd RR. Tag was still on the crate.

So your question should be do I have the correct flywheel? The damper has always been there. Who added the flywheel?
 
Here is a 360 external balancer.

Easy enough to try, if vibration goes away, done deal.

If it is a 1978 360, yes it needs the external balancer, and external balanced flywheel.

Screenshot_20220419-084317_Firefox.jpg


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The 360 balancer is not needed if it was internally balanced. Who put the balancer on the engine and why was it changed? The wrong balancer is not as noticeable as the wrong flywheel at RPM's with rubber mounts while driving down the road.
 
Thanks, the car was not rebuilt as far as I know. It was an automatic 904 and the correct weighted flywheel was installed. the old balancer does have some cracks in the rubber insert so I am going to order a 360 balancer. Thanks again.
 
I should have a 360 balancer. Its your for the shipping. I can look i have a large container of them. In case that is not it you wouldn't be wasting to much money. I also have flywheels neutral and 360. resurfaced ready to install. Steve
 
Oldmanmopar said:
I should have a 360 balancer. Its your for the shipping. I can look i have a large container of them. In case that is not it you wouldn't be wasting to much money. I also have flywheels neutral and 360. resurfaced ready to install. Steve
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Thanks, just ordered one, OH well, Thanks anyway.
 
FYI, could be this was worked on before. Forgot to say the cam gear was 180 degrees out, the dot was on the top of the gear when the dot on the crank gear was on the top!! Seems number one plug was where #3 was? I did change it to the correct timing with both timing marks across from each other. Just got everything together and waiting for the balancer to arrive. Thanks to all that replied.
 
Forgot to say the cam gear was 180 degrees out
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There is no such thing as the cam in “180 out”.
Just turn the crank 360*...... and you’re dot to dot.

If you put the crank/cam at #1 TDC firing, then the dots will both be at 12 o’clock.

Gears set dot to dot is #6 firing.
 
The distributor is the one that can be 180° out, firing #6 when #1 is TDC up on compression. (dot to dot)

Want to drop the distributor in pointing to #1 when the cam gear is at 12 o'clock and the crank gear is at 12 o'clock. #1 up on compression.

Screenshot_20210721-163243_Gallery.jpg
 
Sooo, if gears are dot to dot and #1 piston is TDC , with the distributor in the rotor should point to #1 firing, correct?
 
36DodgeD2 said:
Sooo, if gears are dot to dot and #1 piston is TDC , with the distributor in the rotor should point to #1 firing, correct?
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No, dot to dot is #6 Up on compression stroke, if you point the distributor to #1 you will be 180° off.

Turn the crankshaft one revolution, now that brings #1 up on compression ready for ignition.

Now drop your distributor in there pointing to #1.

Noon and Noon at the dots.
 
Now, If I have dot to dot and the distributor is in, the rotor points toward the driver. With the cap on,is the rotor pointing to #6 or #1 firing.
 
Don't you have someone close by that can help you with this? Friend, Mechanic , Mopar Guy? Watch a YouTube how to video about it.

Screenshot_20220422-195659_Gallery.jpg


This picture Shows the proper position of the distributor and rotor to fire on #1. Cam dots, 12 o'clock & 12 o'clock. Top Dead Center on Compression stroke on #1.

Now if you want to do dot to dot, you roll the engine over 1 revolution, then the cam gears line up dot to dot, that fire on the #6 cylinder, and the rotor now points to the back of the engine to #6. Just the opposite of the picture that shows it is set up to fire on #1.

It's all the same, the fact of the matter is you do not want it firing on the intake and exhaust stroke, that is where being 180° off comes from.

It will not run if you are not firing on compression stroke.
 
I finally got everything correct in my mind. I do have expert help, even though he is a Chevy mechanic! I put everything together and the engine started right up and after cam run in it is running great. Thanks to all that replied, the help was appreciated, especially since the car is running great. Just a bit more of advanced timing and the car will run even better.
 
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