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Match balance a 390 flywheel

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Deans69 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Deans69 Quote  Post ReplyReply Direct Link To This Post Topic: Match balance a 390 flywheel
    Posted: Jul/21/2021 at 10:34am
I was on the phone with Tony last night and I mentioned that I bought a complete 390, totally worked over, Milodon oil pan, Indy oil pump system, aluminum heads, roller rockers, the whole enchilada, and then he dropped the mic with this one, "Did it come with the flywheel?"
Do I have to tear this complete running motor down and have the rotating assembly balanced with the flywheel I have? The flywheel is from my original 390 motor. He said you can't do that unless they are balanced together. Am I screwed? Every time I take a step forward with this car, I take 9 back. It's starting to get old. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RandyB Quote  Post ReplyReply Direct Link To This Post Posted: Jul/21/2021 at 10:42am
Can you call the previous owner and get details, else you have to balance?
Randy B
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73 Charger Rallye 340 triple Blk
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Heavy 488 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Heavy 488 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/21/2021 at 10:47am
Options are
balanced at time of build
Matched to an existing flywheel/ flexplate that came off of that engine
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mbwicz Quote  Post ReplyReply Direct Link To This Post Posted: Jul/21/2021 at 10:57am
  I would also confirm if it has a factory harmonic balancer on it.  If it has a neutral balance harmonic balancer on it, there is a chance that the system was built for a neutral balance flywheel.  Pull off the oil pan and see if there are slugs of heavy metal in the counterweights.  This is common when converting a crank to internal balance.
  The engine builder would normally fill out a balance card for the engine as well.  This would include weights for the piston, pin, rings, and rods.  This would be used to calculate the bob weight.  See if you can find this balance info in some paperwork, there may be a note on what was used when balancing the crank (harmonic balancer and flywheel).
  If you can't find the paperwork, maybe reach out to the engine builder and see if they have any info in their files that may help.

Mike

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Deans69 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Deans69 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/21/2021 at 11:09am
Bought the motor years ago and I have no paperwork with it. Looks to be a factory balancer, nothing fancy about it. 
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Post Options Post Options   Thanks (1) Thanks(1)   Quote SC397 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/21/2021 at 11:40am
Pull it back apart and do it right.  
It will cost you a balancing fee, gaskets, and labor.
The bonus is that you can correct all the things that the previous builder may have forgot like blueprinting the oil system to the distributor gear etc..
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Deans69 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Deans69 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/21/2021 at 11:48am
With a home remodel, 6 car projects and 3 children, the "labor" part is worth more than it's weight in gold. I just have zero wiggle room to deal with surprises. This is an astronomical set back in my world. As for the bonus, the guy had 2 g's just in the oil system, seriously doubt there is any meat on the bones to improve anything. I really didn't want to tear into this thing. 
I literally couldn't touch this car for 2 years, finally make amazing progress because I had some time, and then the hot rod gods just took a huge dump on my head. So yea, it stings. 
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Post Options Post Options   Thanks (1) Thanks(1)   Quote BassBoat Quote  Post ReplyReply Direct Link To This Post Posted: Jul/21/2021 at 12:09pm
Any chance that with all that work it was internally balanced?  That is the only way conscionable that somebody could sell an engine without a flywheel.  Is the harmonic balancer truly a stock external balance?  Look at it carefully.  But you really need to pull the pan and see what you have.  Could be all stock cast pistons and really just fancy go fast parts bolted to it.  In my opinion not well matched at all.  Could be all lightweight forged pistons and H-Beam rods which is what you need to do now while you are taking it apart.  I wish you luck, plenty of help on here to help you figure out what you have, which probably is what you need to do and probably not what you want to hear.
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Deans69 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Deans69 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/21/2021 at 12:17pm
It does not need H-beam rods. I'm not going balls out and doing some insano custom engine work. I tried that with Bulltear and they ripped me off on $900 pistons. There is nothing wrong with putting aluminum heads on an engine regardless of the pistons. 
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Post Options Post Options   Thanks (1) Thanks(1)   Quote scott Quote  Post ReplyReply Direct Link To This Post Posted: Jul/21/2021 at 12:59pm
In another thread you started, you say the engine is installed in the car, with transmission, and is running.
So, how does it run?? Is it as smooth as polished glass all thru the RPM range?? Or does it shake like a 3 legged washing machine on spin cycle with an out of balance load??

If it is smooth as glass, I'd run it as is. If it shakes, well, others have said what to do.
"Prolly" is not a word.
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