5.9 Magnum flywheel - DIY with bolt-on weight??

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Its a flywheel off my 318 magnum "internally balanced" ran it for 2 years on the 318 with no balance issues.
so now i put a 360 magnum in its place I drilled the holes and threaded them 4.9 inches from center on the flywheel so i could bolt the wieght that was on the flex plate to it.

I have the 3.5oz wieght that came off the flex plate bolted the exact same radius away from center and exact same degrees on the flywheel. Im playing around with diffrent wieghts trying to find a sweet spot but im having very little headway lol.

what im really getting at is if you were to add wieght on an internally balanced flywheel for a 360 mag where would you exactly need to place the wieght, TDC? 10 degrees before? this will help me out alot! Thanks!
 
Forgot to mention its a factory flywheel for a 318 mag and Im trying to balance it for my 360 mag. The 360 has the correct harmonic balancer aswell.
 
ok double checked the mopar preformance flywheel and the holes drilled are actually exact opposite of where the wieght is added on my factory flexplate. im still having a very hard time balancing it ive tried over 20 diffrent wieghts! ranging from .08oz to 4.75oz with not much headway
 
was playing with wieghts found one thats very close to balance its 3.45 oz at 4.74" from center. its very close! im learning that you have to be unbelivably percise!
 
http://www.moparchat.com/forums/showthread.php?t=71263

Everything I know about this is in the above thread including a diagram of where the weights go in post #12.

Note the experience of 340Duster1 racing his 5.9 with flywheel balanced substantially different than what I came up with. Perhaps the engines survive without accurate balancing I don't know.

How are you deciding if your engine is balanced?
 
Im going by feel you can notice when its out of balance you can hear it too the way it idles and revs (open headers). I've been doing a lot of math for every weight I added keeping notes on what kind of a difference each one made.

the one thing that screwed me up the most was the 3 holes the factory drilled in the "neutral balance" flywheel. I finally figured out the math on there volume, it worked out to .7oz at 6.36" from center so I had to add that into my calculations finding the correct weight. I will put a post up of when I get it perfect or if my main bearings let loose from being the slightest bit out of balance lol
 
Not sure why a neural balance flywheel would have holes drilled. Do you have a pic?

Sounds like you know very well you might do damage using that method. I imagine you also know there's a lot of things that can make an engine feel like its out of balance (examples: bad plug, bad wire, timing off etc).
 
Just a thought, maybe I missed it, but you are adding the weight opposite where the holes were in the other flywheel, right? I could see that messing someone up, "factory modified the flywheel "here", so that is where I put the weight". Adding weight would be opposite of where you would remove weight.

I'm sure you thought of that, just making sure.
 
Yes the wieght I added is exacly opposite of where the holes are drilled on Idaho's flywheel. I don't have a camera that works but the 3 small holes drilled on the outer edge of my flywheel are actually in the exact opposite location as my added wieght.
At first I thought it was an external balance flywheel, then I realised I ran it on on my 318 for 2 years with no problems lol
 
yeah timing is set 15 initial, 34 degrees total, plugs gapped for .35". I even had each plug wire off checking for diffrence in sound (you could notice when each wire was unplugged).
played with the carb non stop, kindof figuring its not my carb because it was running on my 318 2 days before first startup on the 360.
right now it is smooth as can be anywhere over 1400rpms but then you start to notice it the closer you get to idle. at idle it sounds like it has blower surge or something fluctuates 200 rpms. could it being that little out of balance cause it to idle wierd like that?
 
Idaho. I'm going to be modifying a neutral balance flywheel for use on a LA 360. I will start a new thread when I do it, but I think I can offer you an answer as to why your weight numbers were out, 18.13 in oz instead of 12.825 in oz. I think you will find that the more you spread the removal or adding of weight around the circumference of the flywheel the more you will need to remove or add, because you are moving away from the sweet spot of 41 degrees. If those 3 large holes were closer together then I think you would find that they would be smaller and shallower.
 
Perhaps. But I think not. I believe the combined weight removed will act at the center of the area from which it was removed as if it were removed from one large hole at that point. I could be wrong. We need a physics major.

Edit:

Been a while since I did physics but after posting the above, something twigged. The explanation below demonstrates how vector splitting works. Weight removed from a vector off center from the balancing vector has less effect.

So you are correct. Nice observation.

If the angles of the outside holes are measured one could arrive at the total required weight along the balancing vector. Unfortunately I'm tied up with other things for the time being.

http://reliabilityweb.com/index.php/articles/balancing_weights_radius_changes_and_splitting/
 
Yeah, no wonder it has 3 whopping great holes in it. I am going to external balance a slant six flywheel for use with an LA 360. The stock flywheel will be getting a weight added to it like the aftermarket flywheels do. I will also do another flywheel with balance holes at a greater radius than 3.88. I'm also going to test various home balancing methods.
 
I used the method in the link above to draw a parallelogram with 3 vectors, one for each hole in the flywheel. I set the center vector at 100 mm. The two other vectors came out to 63 mm and 64 mm so I used .635. Here's the calculation.

Total weight = 4.65 oz. 4.65/3 = 1.55 oz per hole.
The distance from flywheel to center is 3.84"

(1 x 1.55) + 2(.635 x 1.55) = 3.52 oz at the center vector

3.52 oz x 3.84" = 13.5 in oz

Feel free to critique the method.

Note that its quite close to the value successfully used by 340 Duster (2.28 oz x 5.625" = 12.825 in oz)
 

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You get the credit for this one. Hopefully the math holds up.
 
Well according to this book,
Chrysler Performance Upgrades
by Frank Adkins
published by CarTech as part number SA-60 in 1999.
ISBN 1-884-089-40-2
The Magnum 360 flywheel counterweight is is 14 oz-inches, which makes your maths pretty much spot on.
 
very interesting. We had quite a few folks searching for that spec on the other forum and nobody ever came up with it. Hence the rigmarole.
Where were you back then? #-o:D
 
Maybe I'm late do the discussion. I bought my flywheel from Bouchillon Performance Engineering
when I installed a 360 Magnum in my 74 Dart. I believe it was very reasonable in price and works great in my Dart.
 
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