gas cranks , balance , flywheels and torque
Here's the scoop
1) ALL, 273/318 LA engines internal balance. both CAST AND FORGED CRANKS
2) All, 360 LA engines external balance, all had cast cranks
3) 1968 to mid 72 340 LA internal balance , had steel cranks
4) late 72 and all 73 340 LA had external balance with cast cranks
340 was dropped in 74 and replaced with the 360 in the hot rod cars. .
273,318, 340 and 360 flywheels ,dampers and torque converters
are not interchangeable as far as balance goes. .
Yes they will all bolt in place of one another but the balance is different between them !
Another sad note is that not all of the flywheels ,dampers and torque converters were identical even for a given engine! Each production run was different...
Yes there was a blueprint spec for weight offset for each given engine.
But on the assembly line is never quite worked out that way. . each run of cranks was a little different !
For example: If you were to order a NEW 340/360 engine from Chrysler. It would ALWAYS come WITH either a flywheel or a torque converter. This was because we KNEW that the new engine would be out of balance and or SHAKE
if the customer used his OLD flywheel or torque converter on the NEW engine !
Yes you can switch them around and get away with is a lot of times. The balance can be off quite a bit before it shakes you to death. . But it in not a good plan...
There are 2 ways to really solve the balance problem in the field.
1) Remove the crank, bolt the flywheel to it . Have them balanced together.
This works fine for manual trans and is cheap...
2) Remove the crank, have the auto trans crank balanced internally. They will use Mallory metal slugs driven into the crank counter weight to do this. Then use a 318 T/Q which is neutral balanced. .
The reason I say this for the auto trans is because you can not balance the crank with the T/Q bolted to it ! You will never find anyone out there that will be able to offset balance the T/Q properly to match your external crank...
We had LOTS of problems in the field with external balance from people replacing flywheels and T/Q's. .
YES you can get away with doing many things incorrectly... .
But what I printed above were the facts for those that are interested in getting the best or correct results. .
Those that are cheap, lazy, or think that they know more than we did.
Then by all means just bolt any of the 318,340 or 360 parts together. LOL
All the holes should line up but some of the earlier 318's used their own flex plate... external balance engines had one hole offset...
I know the solution I mentioned above is not exactly what everyone wanted to hear.
It's a lot of trouble but it does make for a very smooth running engine and saves the front pump bushing in the trans. . Happy balancing.
One last note, In my stash of parts I have a few of the prototype 4 inch stroke cranks from the performance program for the 360 and a few of the
legendary 318 -3 solid steel forged Truck cranks I will never use... .
We got 412 ft lbs @ 3850 rpm out of a 360 that had the 4 inch crank in it. .
The engine had 8. 1 comp. ratio , 2. 02/1. 60 valves , thermoquad carb/ cast iron intake... By the way..... when I speak of math. I am speaking in REAL figures in reality. . Not the fairy tales that were printed in the books by the marketing people ! And production NEVER seemed to go by the engineering blueprints back in the old days either...
Philip said:
Not all of them. I have dealt with 3 cast crank 340's. 2 of them were internal balenced. The third one was a factory goof up. It was stamped 340 on the front of the block. But it was a 360 engine. I took that one apart to make sure what it was. It like to shook the car apart when I started it with a 318 flywheel on it. :-laf
My 73 Dodge performance manual for LA series doesn't say anything about cast crank 340's being external eather.