i called to ask bout getting lower end balanced and they said that he needs my flywheel for my external balanced 406. now i read on here somewhere that i DID NOT NEED to even have my fly with the rest of the stuff when it gets balanced. i was actually told to make sure not to even have them at the same shop at the same time. so....... what gives>>?

i thought i was going to use a neutral balance with the plates so i could buy a cheap aluminum fly, but from what i hear bout street cars, steel would be a little better. so it'll probably be already externally bal. -- no neutral and no plates.

and is $200 for a lowend balance sound bout right or shoould i keep calling round

 

He is correct. $200 to balance a rotating assembly is cheap.

 

you don't want to include the dampner or flywheel as part of the balanced assembly or you'll be stuck using those parts forever or needing to rebalance everything if you want to change them.

 

Ede is correct also. One of the drawbacks to external balancing. Hang on to the bobweight sheet normally provided by the builder. If he does not normally give one to his customers, insist on it. You can reference this years later for part replacement.

 

DO NOT take your flywheel or crank damper to the shop at the same time as your crank and all that. What you will likely end up with, is a one-of-a-kind assembly where ANY part that has to be replaced, will require custom re-balancing, and in order to do that, you'll have to take EVERY SINGLE PIECE back. I.e. something happens on down the road and you need a new damper, you'll have to take your crank and rods out and send them to the shop to have the new damper custom-matched to the other custom-balanced parts. Change from manual to auto, you take your motor apart and send out your crank and rods and new flex plate for re-balancing to each other. Etc.

Have them balance everything TO THE STOCK SPEC. That way, parts from the world at large will still interchange with your stuff; and you can un-bolt and re-bolt stuff, and have it work right.

 

so just give him the crank rods rings etc. and have them balanced to stock spec, then when i take it home i can just bolt the damper and fly on with no problem, (as long as i ordered the right parts)

as long as the dampers in summitt or wherever are to stock spec, cause i sometimes see different size dampers made.

 

All these issues can be solved by getting it internally balanced. Flywheels and balancers are plentiful for internal balance, and since you have it torn down - why not?

I had mine done, so I could use the stock flywheel etc, without having to bother with the "offset weight " flexplate/flywheel adapter thing and a 400 balncer....

 

Why not just have the new "dampener" balanced same as the old one before you re-install it? Same as the flywheel?

 

What if you don't "know" how it was balanced?

Why not just have each part of the assembly balanced to a stock spec (whether internal balance or external), and then you don't have to worry about it any more? No more trips to the balance shop, no "custom" parts, everything just fits, interchanges, and works right.

There's a right way to do things, and then there are degrees of wrong ways. Some are worse than others. I don't see much point in dinking around with "less wrong", when I can proceed directly to "right".... for less money and trouble in the long run.

 

why would you want an external balance vs an internal one?
what is the difference between an external vs internal balance damper and flywheel

 

An externally balanced engine like a stock 400 has counterweights on the dampener and flywheel. An internally balanced engine has all the counterweight mass on the crank, and the dampener and flywheel are neutrally balanced.

 

My machine shop said he needed both the flexplate and balancer to do mine internally. It WASNT CHEAP. It was a 383 external balance crank that I had them internally balance. I think I spent a couple hundred on metal to get it perfect. Also in the Lingenfelter book he said that he wont balance a motor without those parts as well.

 

i don't know much about what all needs to be done to balance a rotating assembly, but i'd suspect using the dampner and flywheel is easier, quicker, or cheaper for them to do it that way.

 

DO NOT let them "custom balance" your parts as a group!!!!!!!!!!!! I cannot emphasize this strongly enough.

What people who know what they're doing actually do, is to balance the rotating assembly as perfectly as possible to the stock spec (whether internal or external balance, there's a spec); and then balance each of the outboard parts as perfectly as possible to their respective stock specs, as well. That way, you have as perfectly balanced an assembly as possible; yet, you retain interchangeability. If you have to replace a part, you simply have your new one set up TO THE STOCK SPEC, which everybody has and everybody can look up in their book, and you DON'T have to get it "matched" to your "custom" one-off assembly.

Like ede said, it's easier to drill a few holes in a flywheel, than to grind little bits of metal off 8 rods. It's the lazy way out. That's why, UNDER NO CIRCUMSTANCES should you allow your external parts to be in the same shop at the same time with your engine's internals for balancing. Unless you can REALLY REALLY trust the shop, you have no way of knowing that some minimum-wage monkey in the shop won't flake out on you, and leave you with a "custom" one-of-a-kind non-standard assembly.

Many shops won't guarantee their engines to be balanced, unless they do the other parts as well. That's fine. JUST MAKE SURE THEY DO THEM AT DIFFERENT TIMES: and that they set up the engine to its stock spec as appropriate, and the externals to their stock specs.

Whatever it costs to have a motor balanced RIGHT, it's worth it. Just write the check and move on.

 

Yeah...the engine will shake itself to death if it's imbalanced...looks really strange, too, watching someone drive down the street with an imbalanced engine.

 

Once again, a bunch of misinformation.

You can give him your dampner and flywheel/flexplate to balance your rotating assembly as long as he DOES NOT add or remove material from either one to balance the rotating assembly.

That's all you need to be concerned with. If he doesn't agree to that then you need to find a new machinist.

 

You DO NOT want to let your assembly be "balanced" this way!!!!

Think of what happens if you hand him a damper or a flywheel that's "out of balance" already. OK, he "balances" your crank to that. Now, you've got EXACTLY WHAT YOU DON'T WANT: a non-stock "custom" assembly; such that if one of those pieces has to be replaced, it will not match the one that your crank was balanced to. Even if your new one is "perfect", your assembly as a whole will be off.

The ONLY way to guarantee that the minimum wage deputy assistant under-monkey at the machine shop won't do himself the favor of sleazing out on your balance job this way, is to NOT ALLOW YOUR EXTERNAL PARTS TO EXIST IN THE SHOP AT THE SAME TIME AS YOUR CRANK. Send them SEPARATELY. If the machinist won't guarantee that he can balance each part separately to stock specs, find a new balance shop.

 

Out of curiosity, what are the balance specs for 400 dampeners and flywheels?

 

Flip that around and think about what happens if you put your "out of balance" flywheel/flexplate and dampner on a rotating assembly that was balanced with something you're never going to use on your engine.

That's why you want him to have YOUR parts. So he can check them for things like this. If he can't, or doesn't, then I'll agree with you on one thing.... find a new machinist.

 

They don't balance the rotating assembly with the balancer and flexplate. THey need them so they can be neutral balanced.

 

well the block is .030 over so i don't know how that "stock spec" part is going to work out. but i'll have a talk with him and reply back with what the man says.

 

As I said, give him whatever he wants, just make sure he doesn't take material off, or doesn't add any material to the flexplate/flywheel or the dampner. That's the only thing you DON'T want him to do.

 

Yup I took mine in but they didnt touch the balancer or flexplate. That would be a fatal move then.

 

I'm with AJ_92RS on this one. The damper and flexplate are counterbalanced to a factory spec. With those, the engine can be neutral balanced. If you need to replace one of the two, and they haven't been altered in order to balance your rotating assembly, you can replace it with another spec part and continue on your merry way.

If your damper or flexplate are not counterbalanced to spec, and the rotating assembly is balanced with them, and the out of spec part is replaced, your rotating assembly will be out of balance.

 

I don't know the stock 400 spec offhand. But it's given as a "moment of inertia", which is basically the product of the "unbalance" mass times its radius from the axis of the part. I.e., if you have a larger diameter part, you don't need as much mass; and vice-versa. But I don't know the exact number, as I don't work in a balance shop; evidently there's some other people here that don't either, and haven't ever been as close to one as I have.

Think about how the factory does this. They make a damper, and they balance it somehow, and they put it in a truck and ship it to an engine assembly plant. It sits on the shelf, presently they pull it and stick it on an engine as it rolls down the assembly line. Note that it isn't "matched" to that engine. Note also, that the engine was balanced before it was assembled, which is to say, long before that damper ever got close to it; and they didn't need the damper to balance the engine. Likewise, they made a flywheel or flex plate in its plant, and shipped it to the engine plant, and the same thing happens with it; again, they don't need it to "match" the engine to it, or it to the engine. They made it right in the first place, so now any engine fits any flywheel and any damper. We call this "mass production". It's the hallmark of the Industrial Revolution. Someone smarter than most of us (speaking strictly for myself) figured this out about 200 years ago. Go look up Eli Whitney, and check out his musket factory invention where he eliminated hand matching of finished parts to each other (sound anything like engine balancing?), and learn about the advantages of making every copy of the same part identical so that no hand-fitting is required.

So now here we are out here in the real world. We have this engine we want balanced. What do we do? Do we go get a damper and/or a flywheel, and "match" this engine to those? If we did, what would then happen if we wanted to, say, swap the car from a manual trans to an automatic? How would we then "match" the engine to this new piece? Why should we bother, if we had done it right in the first place?

How can anyone fail to see how STUPID it is to balance an engine and its externals TOGETHER? The right way to do this is to balance each part TO ITS STOCK SPECS, and retain interchangeability that way. There is NO ADVANTAGE to doing this ANY OTHER WAY, than balancing each piece to its stock spec, whichever stock spec applies to it.

Remeber now, I'm sofakingdom, I have trouble understanding this; so help me out here. I'm really struggling with the concept of how it's better to deliberately screw up an engine so that it has to be taken apart and re-balanced whenever a bolt-on part wants to be changed.

Since the machine shop shouldn't take off or add material to the externals, then he doesn't need them to balance the engine. If the engine is out of balance (with respect to its stock spec, that is) without them, then the engine should be balanced properly. If the externals are out of balance, then tehy should be balanced TO THEIR STOCK SPEC, independent of the engine. To balance the engine properly, the externals are NOT NEEDED, and since they're not needed, they SHOULDN'T BE THERE, so that the machine shop is therefore denied the opportunity of creating you a headache and instead is left with no possible option other than, to do the job right.

 

Production balancing on the whole isn't that close. That's why in a custom balance, you'll have all rods matched to the lightest rod (each individual end, actually), pistons matched to the lightest piston, etc. The rings and bearings don't tend to contribute that much to the scatter.

Neither do the damper and flexplate. Although there are tolerances to the weighting, they aren't going to affect the outcome nearly as much as the rods/pistons/pins. It's just easier for the customer balancer to use the weighted damper and flexplate than it is to add those weights to the crank when spinning it. Since you're already spending good money to get it custom balanced, it doesn't make much sense to pay them even more to add the "factory spec" weight that is already available with your damper & flexplate.

The machine shop isn't stupid, they're being lazy. In this case, their laziness isn't going to cost you anything, nor reduce the quality of what they produce. Just give them the damper & flexplate.

(Same goes for a one-piece rear main seal crank - just give them the flexplate.)