Flywheel cast versus steel crank?

[moparnut]

Is a flywheel the same if the motor has a cast versus forged crank?For instance in my swap where i am pulling the numbers 73 340(cast crank) in my challenger and installing a 69 340(steel crank) with truck od bell,833od,flywheel out of the truck ect.Are all 10.5 flyhwheels interchangeable and do all have 130 teeth?I know the balancer is different from cast to steel but what about the flywheel?Do i have to have it separatly balanced or take the new motor in for balancing with it on?I think the 69 340 engine had an auto trans before it was rebuilt,I bought it rebuilt but never ran so i am unsure of the external balancing,if it was done with flexplate or flywheel,sorry for all the ?'s just trying to learn more....again,lol
thanks

[Mopar73340]

The cast crank flywheels are balanced differently, you will need to have the cast crank flywheel you have neutrally balanced to use with the forged crank. You will also need a forged crank vibration damper.

[moparnut]

thanks,The engine is a forged crank engine as would be the balancer(vibration dampener)so all i guess i need to do is have the flywheel nuetrally balanced(if i use the one i got with the od bell)or i could use the other flywheel i have that was a forged crank flywheel.

[Mopar73340]

or i could use the other flywheel i have that was a forged crank flywheel.

Use the forged crank flywheel. Depending upon where you are in your engine build, I would have what you are going to use all balanced together.

[moparnut]

The enigine is done,bought it that way,like i said i dont know if it was in front of a manual or auto tranny,which is moot.I would assume since i know the guy who built it(I know it was balanced) that is shouldnt matter if its cast of forged if the flywheel is neutrally balanced(the engine rotating assembly was internally balanced)Correct me if i am wrong

[Mopar73340]

The forged crank flywheel will be neutrally balanced and work correctly, or you can have the cast one balanced neutrally, and use it. (I had to do this with mine a few months back) It was cheaper to get the cast one balanced than get a new one.

[ShelbyDogg]

Moparnut, Funny that you posted about this.  I bought a 73 cast crank 340 with a 727.  Putting a 4 speed behind a 340 cast crank, require offsetting the balance by 4.2 oz in a certain area of the flywheel by drilling a couple of holes.  That was one of my first questions months ago on this site and I had the answer right here in my Direct-><-Connection BiBle.   I have to have mine drilled to match my motor. Your flywheel has to be a special modified one, if it came on a CAST crank engine. 
Rob


Edit...
I read your post again.   Keep the flywheel that came with the cast crank motor with it forever.   Use the zero balanced one on the 69 340. ( I found a flywheel at a mopar swap meet for $20 and will balance it for my cast 340)

[moparnut]

Now you have me wondering...I never really paid attention if my numbers 73 340/4 speed might be forged crank,I just assumed it was cast since all 73 340's were cast crank,I'll have to go look at it.
I dont have a motor with a cast crank(unless the above mentioned is)I have one nicely built  69 340 on an engine stand for my chally,another 70 340 apart for a spare and the one in my chally.
Is there any down side to neutrally balancing a cast flywheel for a forged engine?

[Mopar73340]

Is there any down side to neutrally balancing a cast flywheel for a forged engine?


All flywheels are balanced one way or the other at some point and any good machine shop should be able to balance it however you need it.

[moparnut]

EVERY 340 4speed came with a forged crank. 

Rob you sure about this?I just checked my Chally and it has a cast crank balancer and is numbers matching.Now when i bought the car the owners parked in in the garage because of a vibration after a rebuild,I assumed it was because they used the wrong flywheel but could be they put a cast balancer on a forged crank(although i dont know why they would).When i asked them about the rebuild they said they didnt take the balancer or  flywheel in to the shop when they balanced the engine,which could be the real reason for the vibration also,since a cast crank is externally balanced.How can you tell if it is a cast or forged besides the balancer and without pulling the oil pan?How do you tell with the oil pan off?I guess i will find out when i pull the motor and put in the 70 340,which may be a couple of months or so when i get the time

[aarsteve]

Balancers on cast crank motors are alot wider than the ones forged crank 340s also they normally are stamped in the front of them saying only for certain use.

[moparnut]

Yes i know all that,the question was how do you tell if its a forged crank without looking at the balancer and without looking inside the engine?I dont think you can,I think I will have to drop the pan when i remove the engine to be sure

[ShelbyDogg]

  MY IMAGE BELOW IS FROM A BOOK DATED FORM THE MID '80s so newer stuff doesn't apply..

If you don't know if you have a cast or forged crank, you have to drop the pan to look at the chunks of steel between the machined journals for a wide or skinny parting line. If that motor was balanced without the balancer or flywheel, get rid of that cast balancer and try a neutral balancer.  When I have my flywheels checked, even the factory balance is off a little. This is the reason to give everything to the shop doing the balancing.

Here are the drilling templates to offset a neutral balanced flywheel to use on any cast crank engine, or a 440 steel crank with 6pack rods.   This only works if you have an unmodified production balance. 

Rob

[ShelbyDogg]

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[moparnut]

Thanks,I was unsure about the 73's until i looked at mine.The numbers motor is coming out anyway,I was told before they garaged it,which is one of the reason i got it so cheap(2000 bucks) was there was metal shavings in the oil after the rebuild,the seller was clueless about engines.Thats why after gathering all the evidence and asking a ton of questions(I'm good at that,lol)I came to the conlcusion is was balanced incorrectly as i perviously stated.I think it was biting into the main bearing,hence the shavings,doesnt really matter since i wanted a built 340 in it and wanted to rebuild and bag the original numbers stuff.