Balance question

[RattyBarracuda]

Here's a question. I've got a 318 cast crank cut .010 and .010, im using eagle rods that are all weight matched and KB pistons that are all weight matched. I know the crank i'm using is an internal balance from the factory. should i rebalance the crank? If im only going to be running this engine on the street and not racing it at all would rebalancing it be a major issue if i skipped it and just put the shortblock together with what i have?

 

[PDQ340]

Here's a question. I've got a 318 cast crank cut .010 and .010, im using eagle rods that are all weight matched and KB pistons that are all weight matched. I know the crank i'm using is an internal balance from the factory. should i rebalance the crank? If im only going to be running this engine on the street and not racing it at all would rebalancing it be a major issue if i skipped it and just put the shortblock together with what i have?

You'll most definitely want to have the assembly balanced, because you can count on the aftermarket parts not weighing anywhere near the same as the factory pieces. Unless they've been lightened, they'll likely be significantly heavier than OEM. Having the assembly balanced will give you peace of mind when you turn the key the first time. Not having the assembly balanced will very likely mean you'll be pulling & disassembling the engine to have it done.

Bryan

 

[75greenduster]

I would think those rods and pistons would actually be lighter than stock. I remember someone on here used those same rods and pistons and said the machine shop removed almost a pound of metal from the crank when it was balanced. I would get it balanced.

 

[Mrmopartech]

If you are using the KB hyper pistons,they will be lighter and this throughs off the bob weight on the crank.Weather the assembly is heavier or light,it has to be rebalanced,Mrmopartech

 

[dusterdon]

Chrysler never made a cast crank that is internally balanced. They're all externally balanced. They did make a lot of 318 cranks that were internally balanced though. They were all forged.
Anytime you change a piston or connecting rod the engine (crank, rods, and pistons) MUST get rebalanced. The only time you can get away with it is if you are using stock rods and replacement cast pistons. The weights are close enough for a street car. No one uses cast pistons in a race car.

don

 

[RattyBarracuda]

all 318 cranks are internally balanced. 360 are external. forged 340s are internal and 72 - 73 cast 340s are external. thanks for the advice guys, i'll be sending the assembly out at the end of the week.

 

[triggerjay]

Makes me think. I just started our motor today for the first time. It is a 318, bored 30 over, 10 10 on the crank, hyperutectic flat top pistons. When we took the motor to the machine shop, the motor had the crank, old rods, and old pistons in it still. When they guy at the machine shop saw I had stock skinny 318 rods, he told me he had a set of stock 340 rods in the back I could have, so I had him resize the 340 rods for the new bearings. (340 rods are the same stroke, just thicker) He sent my crank out to be turned, and hung my pistons on the new rods. I did the rest of the assembly from there. But I do not know if he balanced the crank???? I never thought about it untill now. The motor is in, and runs great. Is there any way I can tell, or any way I would know if it has been balanced? and if not, what problems can, or will arise from not balancing it? Do I need to go back to square one and pull the motor? This is my first motor rebuild. Needless to say it was a great feeling to hear it run! O

Triggerjay

 

[1969340dart]

I would have to agree with the balancing of it.I personally would have any and all engines balanced! That is just my opinion

Bobby

 

[moper]

I would have to agree with the balancing of it.I personally would have any and all engines balanced! That is just my opinion

Bobby

I agree. All my engines get internal balancing. The only way to fly...

 

[redfastback]

ragardless of internal or external balancing, everybody here is right. when you change the dynamics of the engine, be it only pistons and rings and bearings, they are new and may not weigh exactly as the old stuff. it is cheap insurance since it is all the way inside your motor. balance the rotating assembly.