Talk about making things far harder than they really are. Damn.

Technically it's against the weight that's stuck to the torsional damper, not the crank.

I'm sure in your research you did a search on this site correct? This has been covered before, but you knew that right? No, well let me pull out a volume or two out of the handy dandy den library thusly allowing me to reach into the grave and see what John himself says:

Clear now? No? Ok...

See, what you are failing to realize, and the point that many have vainly tried to make, is that you are not looking at the whole damn thing. The flywheel is balanced offset to the torsional damper. Every car. Every time. You DO NOT balance these engines like the traditional externally balanced motors Like say a 400)!!!!!!! Clear enough? No? Ok...

Think on this, why is it the damn thing only bolts up properly ONE WAY? Just a fluke of production? Do you truly think that GM engineers are that inept as to not think this through in their redesign? well, that's possible...

Since the company that actually produced the vehicle doesn't have one, and the tech who is paid to specialize in the repair of said vehicle had to spend 15 minutes searching for some mention of it (plainly suggesting that he was clueless about this allegation) one could come the the wholly reasonable conclusion that the spec you are looking for does not exist.

That conclusion is patently wrong on the face of course, but I would venture that you could find from a manufacturer the weight spec and radian of placement on the flywheel/flexplate.

Ok, let me set you on the path of the right question to ask...

Q: In relation to the torsional damper, what is the acceptable specification for the weight and radian placement on the flywheel in order to return the whole of the 'crank assembly' to 'neutral' when you use a new flywheel with a used torsional balancer on the other end of the assembly.

A: Who bloody really gives a rat's droppings if it's not a race motor?!? Pick one on the parts shelf that has been manufactured to within those elusive specs because quite honestly no shop really wants to mess with this nonsense minutia as it's been taken care of well before the first production engine came out for sale to the public and it will most likely be a waste of the shop's time and energy and the customer's money.
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Yes Virginia, that means you should have just listened to this answer and had done:

 

If you're building a racing engine that's going to spend it's entire service lifetime of one whole hour spinning at 10,000 RPM before being thrown away or rebuilt, and you want what some would arguably believe is the best possible balance achievable by mere mortal humans, then by all means go ahead and have the shop do whatever they want to modify the flywheel/flexplate along with all the rest of the rotating assembly parts. In this case, the flywheel/flexplate is going to outlive the engine, so you don't care.

If you're not building that engine, and you want to drive a car that you can drive on the street for as long as you like without having to pull and rebuild the entire engine just to change the flywheel/flexplate, then use an off-the-shelf flywheel/flexplate that's balanced to the stock specs, whatever the stock spec happens to be for your particular 1 or 2 piece RMS block. Will it be balanced about as well as any engine ever was from the factory? Absolutely. Will it be absolutely, completely, 100% perfectly balanced? Almost certainly not. Will you ever be able to tell? Almost certainly not. If you think you can discern some miniscule vibration, then you could resort to the aforementioned completely unscientific trial-and-error methods proscribed by the service manual to try to make minor corrections to the balance, even though that's not the "best" way to do it.

If you have a 1 piece RMS block, and you buy a flywheel/flexplate that's neutrally balanced, (notice not internally balanced, and not externally balanced. Those terms have absolutely no useful meaning when referring to 1 piece RMS engines), then you will need to have weight added to the flywheel/flexplate to bring it back to the specs of a factory flywheel/flexplate, which is not neutrally balanced.

 

As much fun as this is, I'm growing weary. Adults just agree to disagree, shake hands and move on. Name calling, and sticking your tounge out is for kids. Have a great day!

 

In review

PRICELESS!

 

Wow, I acctually just read this entire thread.

I bought a motor last year, it was internally balanced. i bought an ATI damper for an internaly balanced motor, then I found a flywheel that came with a T-56. The fly was made for an internally balanced motor. I bolted it on. almost 2000 miles later and a lot of "FUN" time, and she has no vibrations at all.



just get the fly balanced, if you wanna play it safe, buy a new damper that is zero balanced too. Bolt them on and DRIVE.

 

According to Centerforce catalog, its a 23.4 in/oz imbalance/counterweighting. They actually sell them this way, ready for use. Weird huh? I dont know what Fidanza's problem is.

I dont know why you arent using your head personally. As I mentioned before, go anywhere and ask for a FLEXPLATE. They'll look it up and pull exactly the same item off the shelf every time. As always, you install it on the car, and drive it away. There's no questions, no rocket science, no screwing in weights, its ready to go and with a 1 piece rear main it has a weight attached. You dont cut this weight, adjust it, or anything. You run it. Its because there IS a specification for how much weight there needs to be and where. Its no different than a flywheel in that regard. The imbalance is related to the crank, not that its a stick or auto.

And if you think an imbalanced flywheel cant be balanced alone.... I dont know what to tell you. Every single small block Ford is like that, and its never been a problem. And they have 2 different weights just like Chevy its just that both of them are imbalanced rather than 1 being zero/neutral. Here's some more info for you since you've never dealt with balancing engine parts before, apparently...
http://www.goodson.com/technical_sup..._balancing.php

Oh and I love that manual
Note it doesnt say eliminated. I guess if you want to tear up your main bearings by playing guessing games with weights, be my guest. Not my engine.

 

I called the tech dept at Centerforce, and got voice mail. I asked them to give me a call back.

I looked at their flywheel info, and I'm quite sure the 23.4 imbalance is how the Fidanza is built too.


This is cut and pasted from the bottom of the flywheel page........


1 - All Centerforce counter balanced flywheels are rough balanced. We do not recommend aluminum flywheels for street applications. SOME ALUMINUM FLYWHEELS ARE SPECIAL ORDER ITEMS, PLEASE CALL FOR AVAILABILITY

No way would I call "rough balanced" a "ready to use product".

I ask you this.... isn't comparing a solid metal flywheel with a solid metal pressure plate attached, and a flex plate with a fluid filled viscous clutch bolted to it a little like comparing apples and oranges? I could see the fluid dampening property's of the torque converter canceling small imbalances that might exist. On the other had with a light weight flywheel the lack of mass could exacerbate the condition.

Something is prompting these companies to say things like "must be balanced to match existing flywheel" "rough balanced" and "not recommended for street use" I have a feeling that last one is for people who just want to slap a rough balanced flywheel on and have it run smooth as silk with they're poly motor and trans mounts.

I will follow up with Center Force, and ask them why they only rough balanced. Thanks for the input Madmax.

Centerforce just called me back while I was sitting here. He gave me the figure 75% of people bolt and go, and "usually" the factory tolerance is close enough to not cause a problem. 25% of the time people go ahead and have them checked with the crank to be sure. He did say if your car didn't vibrate before to match your new one to the old one to be sure. Basically no guarantee's but your odds are good that there won't be a problem.

 

The torque converter doesn't really have any fluid balancing properties since it's completely filled with fluid with no air space. It's true that the flexplate and converter together have much more mass than a flywheel alone, but the converter itself is perfectly neutrally balanced so it may as well not exist as far as balancing is concerned.

If I had to guess why they're only selling "rough balanced" flywheels, it's probably to reduce manufacturing cost. It's easier to produce a line of neutrally balanced flywheels than a number of non-neutrally balanced ones. For that matter though, stock engines can be considered only rough balanced, since they don't all get individual treatment.

 

See:

Liability; Vicarious Liability; Affermative Defense... and probably a half dozen more, but that should give you your answer right there. If you are expecting to get this direct of an answer from a manufacturer, well, don't.

Try: http://www.lectlaw.com

And the dampening is done by the torsional damper, which you do have (one hopes) not the torque converter.

 

I have to say Centerforce was much more willing to stick their neck out on the phone than Findanza was. I like their odds better than the 50/50 I was giving it. It's food for thought.