Crank and balance

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ihave67cuda

ihave67cuda

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Hello everyone,

I am confused and have a problem. Hopefully you all can steer me in the right direction.


I have a 340 that is currently being rebuilt.

I have:
-cast crank
-harmonic balancer (no counter weights)
-and a torque converter also without counter weights.

THE ONLY PART I CAN TRUST IS THE CAST CRANK ITSELF. The Torque converter has been added by a local transmission shop...

1. Do these parts add up?
2. Are cast cranks internally ballanced or externally balanced?
3. If cast cranks are externally balanced, shouldn't the torque converter and harmonic balancer have counter weights?

As side notes:
before the engine rebuild and after the added torque converter, I was receiving a continuous (lopping) vibration in the car that appeared to be coming from the transmission. This only occured at coasting speeds and at idle when revved around 2.5k or more.

my rocker shaft split in four places at the hold down points just before the engine rebuild.

I had a local engine shop balance all the recipricating parts to include the crank.
 
ihave67cuda said:
Hello everyone,

I am confused and have a problem. Hopefully you all can steer me in the right direction.


I have a 340 that is currently being rebuilt.

I have:
-cast crank
-harmonic balancer (no counter weights)
-and a torque converter also without counter weights.

THE ONLY PART I CAN TRUST IS THE CAST CRANK ITSELF. The Torque converter has been added by a local transmission shop...

1. Do these parts add up?
2. Are cast cranks internally ballanced or externally balanced?
3. If cast cranks are externally balanced, shouldn't the torque converter and harmonic balancer have counter weights?

As side notes:
before the engine rebuild and after the added torque converter, I was receiving a continuous (lopping) vibration in the car that appeared to be coming from the transmission. This only occured at coasting speeds and at idle when revved around 2.5k or more.

my rocker shaft split in four places at the hold down points just before the engine rebuild.

I had a local engine shop balance all the recipricating parts to include the crank.
Click to expand...

cast 340 cranks are externally balanced unless the machine shop internally balanced it..

you need to talk to the machine shop that balanced the engine...look for mallory metal on the front and rear crank counterweights..

otherwise.....the balancer for a cast 340 cranks says for cast 340 crank only...and the it needs a weighted converter...
 
ihave67cuda said:
Hello everyone,

I am confused and have a problem. Hopefully you all can steer me in the right direction.


I have a 340 that is currently being rebuilt.

I have:
-cast crank
-harmonic balancer (no counter weights)
-and a torque converter also without counter weights.

THE ONLY PART I CAN TRUST IS THE CAST CRANK ITSELF. The Torque converter has been added by a local transmission shop...

1. Do these parts add up?
2. Are cast cranks internally ballanced or externally balanced?
3. If cast cranks are externally balanced, shouldn't the torque converter and harmonic balancer have counter weights?

As side notes:
before the engine rebuild and after the added torque converter, I was receiving a continuous (lopping) vibration in the car that appeared to be coming from the transmission. This only occured at coasting speeds and at idle when revved around 2.5k or more.

my rocker shaft split in four places at the hold down points just before the engine rebuild.

I had a local engine shop balance all the recipricating parts to include the crank.
Click to expand...

I wonder if someone used a 318 crank on a previous rebuild..they are cast and internally balanced. What is the casting number on the crank??
 
The only way to be dead nuts 100% sure is to take it to a shop with a balancer and have it checked. Cast cranks require weighted balancers and weighted converters. Steel cranks have neutral balancers and no weights on the converter. As stated, unless your crank has been balanced to match your balancer and converter, you have mismatched pieces. Are you 100% certain your crank is cast?
 
ok,

All this helps.

It is a 340 cast crank.

I have a stock harmonic balancer that reads "use with 340 cast crank only" that came off the engine when the rebuild started

.....I had the engine shop balance the crank and parts with a harmonic balancer that is not stock and does not read "use with 340...I guess my question now is do I need a new crank?
 
did the machine shop give you paper work that shows the pistons/rods/ weights...and then the calculated bobweights?


you dont really need a new crank...you just need a crank that is properly balanced for the rotating weight of your engine
 
i did receive paper work that explained the balancing and all the weighting.

The cast crank was balanced with the piston assembly with an aftermarket harmonic balancer without counter weights.

the torque converter (without counter weights) was not balanced when the crank, harmonic balancer and piston assembly was balanced

would this work? would I need a counter weighted torque converter and have it re-balanced with the crank, har bal, piston assembly?
 
If the shop balanced it without a torque converter I can't see why you'd need a converter with weights but I'd call them and ask them. Since they did the work they know a lot more than we do of what is what. We know what stock is and method's of balancing but we don't know what they did.
 
If the harmonic balancer that was used in the balancing was a neutral balance unit then the engine was internally balanced and any neutral balance harmonic balancer or torque converter can be used. That means no balance/counter weights on the balancer or torque converter.
 
Sounds like they did it right. The only way to know is CALL and ask them. That's three times that this has been recommended now. Call um and let us know. From the sound of it, they got it right.
 
ihave67cuda said:
ok,



I have a stock harmonic balancer that reads "use with 340 cast crank only" that came off the engine when the rebuild started

.....I had the engine shop balance the crank and parts with a harmonic balancer that is not stock and does not read "use with 340...I guess my question now is do I need a new crank?
Click to expand...
Sounds like you need a new balance shop. He balanced the crank to a neutral balancer, not yours. If you use your 340 cast balancer, youll be out of balance as the 340 cast balancer had a huge egg weight on it. You can use an LA 318 balancer as they are all neutral as well as a neutral balanced convertor and flex plate, no 360 or B/M weighted flexy.
 
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