TKX Post Swap RPM Related Vibration

[BSB67]

I gotta ask. How did you not see this when taking off the converter to flexplate bolts?

 

[1970DCH]

I don't remember you stating the engine size before. In fact I'm having difficulty even now since it seems that you have a 318 but in the PM you state that it has a 360 rotating assembly.
That is an unusual combination. I'm guessing it was to increase the stroke using a 360 crank?
Nevertheless, this balance job:

View attachment 1975083

Looks like the work of an idiot. NONE are factory and they sort of oppose each other. It looks like an attempt to compensate for an internal imbalance by trial and error without removing the transmission. You see, you can unbolt the converter, slide it rearward, rotate it enough to get a MIG nozzle in there and tack weld the weights without removing the transmission.
Some will say You got it working, no need to worry about why it wasn't right before but I am naturally curious and hate to deal with not knowing why. It is great that you got it figured out but I'd still be wondering why-why-why ???

I’m very curious as well. I was told that the engine was originally a 318 that was stroked to a “355” via an old company in Sothern California named Speed-o-motive a long time ago, along with 360 heads and a cam. What makes a 318 able to be internally balanced and a 360 external?

 

[1970DCH]

I gotta ask. How did you not see this when taking off the converter to flexplate bolts?

Whether it was balanced internally or externally was not on my radar. When going through this process with SST, I was asked if the engine was internally or externally balanced and I responded that it was a 318 stroked to a “355”, at which point I was instructed to look at the flex plate. In doing so, it was concluded that because the flex plate had no weights, it was internally balanced. I literally did not notice these in the torque converter because I wasn’t looking for them there; when I removed it, I immediately put that side down so more fluid didn’t leak out on my floor.

 

[1 Wild R/T]

Thing is, with the weights cancelling each other out... You have no idea what the correct weight is, you know it shakes with zero... And I'm willing to bet it'll shake with the 360 weight...

The correct way to sort it out would require tearing the engine down & measuring the weight of rotating components... Somehow I'm betting you don't want to do that....

So, if it didn't have any noticeable vibration as it was set up I suggest having the old torque convertor spun on a balancer, use that number to add weight to your flywheel...

Might even go as far as seeing if some small block Mopar had an OE balance close to what gets measured & use that number...

 

[1970DCH]

Thing is, with the weights cancelling each other out... You have no idea what the correct weight is, you know it shakes with zero... And I'm willing to bet it'll shake with the 360 weight...

The correct way to sort it out would require tearing the engine down & measuring the weight of rotating components... Somehow I'm betting you don't want to do that....

So, if it didn't have any noticeable vibration as it was set up I suggest having the old torque convertor spun on a balancer, use that number to add weight to your flywheel...

Might even go as far as seeing if some small block Mopar had an OE balance close to what gets measured & use that number...

I am thinking about checking to see what that converter checked. I already added the weight for a 360 and there is no noticeable vibration…I’ll take it for an extended drive today just to be sure.

Having said that, Kern Dog mentioned these aren’t standard weights, so it could be they just used whatever they had on hand and eventually came close to the 360 spec weight by countering the counter weights.

 

[1 Wild R/T]

I am thinking about checking to see what that converter checked. I already added the weight for a 360 and there is no noticeable vibration…I’ll take it for an extended drive today just to be sure.

Having said that, Kern Dog mentioned these aren’t standard weights, so it could be they just used whatever they had on hand and eventually came close to the 360 spec weight by countering the counter weights.

If you're happy with it I'm happy... But I tore down a 340 that was wrong a few years ago... It had really unusual bearing wear & wear on the crankshaft rod throws....

 

[RemCharger]

I am thinking about checking to see what that converter checked. I already added the weight for a 360 and there is no noticeable vibration…I’ll take it for an extended drive today just to be sure.

Having said that, Kern Dog mentioned these aren’t standard weights, so it could be they just used whatever they had on hand and eventually came close to the 360 spec weight by countering the counter weights.

Pretty sure that's what happened. I'm guessing they used one of those dynamic on car wheel balancers. I had thought about that on a 440 I had a problem with once

 

[1970DCH]

If you're happy with it I'm happy... But I tore down a 340 that was wrong a few years ago... It had really unusual bearing wear & wear on the crankshaft rod throws....

The right thing would be to open it up, I agree. This engine has had a few other issues, though, so I may just run it and put further time/money towards a new engine when that time comes.