How bad would an engine run if……

[Moparfiend]

How bad would an engine run if the engine was internally balanced but used a harmonic balancer and flex plate that were weighted for an externally balanced engine? How would it idle and also how would it cruise at 60?

Also is the balancing of an automatic the same as a 4 speed? Meaning the flywheel is also weighted similarly as flex plate?

 

[pnora]

How bad would an engine run if the engine was internally balanced but used a harmonic balancer and flex plate that were weighted for an externally balanced engine? How would it idle and also how would it cruise at 60?

Also is the balancing of an automatic the same as a 4 speed? Meaning the flywheel is also weighted similarly as flex plate?

Run fine. Shake can feel like a miss. Just shake Bad. Like a dog pooping razor blades. 4 speed or auto have balanced flywheels, flex plates, torque converters on internal vs external balance.

 

[Dave6T4]

It would run, but I think it would be hard on the engine's main bearings, over time.

 

[Kern Dog]

Automatic flywheels were not balanced until the Magnum engine series in the 90s. The torque converters were though.
The engine will run the same but yeah....it will shake. That is good for nothing.

 

[TN Mopar]

I couldn't do
There is just something about feeling smooth power that you built with your own hands
And knowing its right

 

[Darter6]

Sister ran her 69 440 NewYorker out of oil so we implanted a free 77 400 in it and sold the car.
400 external balanced but used the 440 and 727 flex plate/torque converter. Had a vibration at idle but ran down the road fine.
The guy that bought it drove it for years till rust took it out of service.
Not saying it was right or ok to do. When you are broke you do what ya can.

 

[4mulas]

Automatic flywheels were not balanced until the Magnum engine series in the 90s. The torque converters were though.
The engine will run the same but yeah....it will shake. That is good for nothing.

Flex plates?

 

[RemCharger]

I ran a 77 440 that came with a internal balanced balancer / TC,, it shook. But survived many passes and nitrous runs before it was corrected. Then ran for years as a bracket engine. Amazing the engine never really seemed to care.

 

[Moparfiend]

Thanks guys. I am chasing a vibration. The engine idles a little rough but at 50 the vibration is noticeable. The reason why I asked because if it was crazy, crazy vibration then that wouldn’t be my problem, but if it’s a mild vibration, then it still could be the issue as I don’t have the build history on my motor. It’s a 73 340 which in stock form would be externally balanced but it ain't stock. I assumed it was externally balanced when I installed it.

I just pulled my drive shaft and inspected it. Looks in really nice condition and the u-joints are all free. So tomorrow I plan to have it checked for balance to rule out that.

 

[RemCharger]

Run it up to 1800~2000 in neutral and watch your rear view mirror,, or console. If it's smooth, it's not the motor.

 

[Lefty71]

I have no (bad) experience with this. Does anyone here think that the vibration can be noticed free revving the engine, or just at a certain rpm?? This would eliminate the drivetrain factor, sans converter and flex plate, and make it a lityle easier for the OP to solve variables??

 

[33 IMP]

How tight are the fillings in your teeth?

I think if you had internal/external balance problems, you'd know it.

 

[33 IMP]

If it vibrates at 50 mph, note rpm.

Then free rev it to same rpm in your driveway in neutral.
If the vibration is the same.... it's in the motor or trans.
If it's gone, or much less, your problem is in something ELSE, that rotates down the road.

 

[RemCharger]

I have no (bad) experience with this. Does anyone here think that the vibration can be noticed free revving the engine, or just at a certain rpm?? This would eliminate the drivetrain factor, sans converter and flex plate, and make it a lityle easier for the OP to solve variables??

That's why I posted #10.
The harmonics are like 1800,, 3600,, and so on

 

[Moparfiend]

Run it up to 1800~2000 in neutral and watch your rear view mirror,, or console. If it's smooth, it's not the motor.

It’s smooth. I was just curious how bad a miss-balanced motor would behave. If obnoxious then I could assume it’s and externally balanced crank and thus set up is ok.

 

[Kern Dog]

In 2022 when I had the engine out due to a bad cam, I bored it out another .010 to ,040 and bought new pistons. The first set came from a vendor that charged extra for balancing, which I approved. The first combination ran fine but was never a smooth idling setup. The rebuild in 2022 included a balance job at a local shop and either I got lucky or this shop here did a phenomenal job. Even with a huge cam, the car idles great and runs strong. It is a bit soft below 2500 rpms but it does not shimmy like I pulled off 2 plug wires.

 

[Demonic]

I just had a friend find out his 360 was miss-assembled with the wrong balancer for a 78 360. It was blowing oil out the exhaust and the bearings were worn to copper. It has been on several long distance trips from MD to Detroit and MD to Pigeon Forge. Getting fixed now.

 

[Roadhog51]

I had a later 383 with a cast crank and 4 speed. I always thought it had a strange vibration under load. After 3,000 miles the vib dampener started coming apart and rubbing on the TC cover. A different flywheel and a different dampener fixed it!

 

[Dodge-Scatpack]

Automatic flywheels were not balanced until the Magnum engine series in the 90s. The torque converters were though.
The engine will run the same but yeah....it will shake. That is good for nothing.

I believe the 5.2 magnum is internally balanced whereas the 5.9 magnum is externally balanced. Kevin

 

[Moparfiend]

I had a later 383 with a cast crank and 4 speed. I always thought it had a strange vibration under load. After 3,000 miles the vib dampener started coming apart and rubbing on the TC cover. A different flywheel and a different dampener fixed it!

I had thought all 383’s were forged cranks?