454 clutch balance

[Roger G.]

I am replacing the clutch and flywheel on my 70 LS5.
The flywheel came from NAPA, appears to be manufactured by LUK.
I haven't bought the clutch yet.

It was suggested I should have the clutch and flywheel balanced.

The 454 is externally balanced. Seems to me the flywheel cannot be balanced without taking the rest of the rotating assembly into account?

I can understand balancing the pressure plate to neutral so it adds no influence to the overall balance.

What is commonly done for the 454?

I have never had a pressure plate balanced. This is new to me.

[Joe L.]

Re: 454 clutch balance

I am replacing the clutch and flywheel on my 70 LS5.
The flywheel came from NAPA, appears to be manufactured by LUK.
I haven't bought the clutch yet.

It was suggested I should have the clutch and flywheel balanced.

The 454 is externally balanced. Seems to me the flywheel cannot be balanced without taking the rest of the rotating assembly into account?

I can understand balancing the pressure plate to neutral so it adds no influence to the overall balance.

What is commonly done for the 454?

I have never had a pressure plate balanced. This is new to me.

Roger------


Look at it this way: when a new 454 externally balanced SERVICE flywheel is purchased from GM it is balanced out-of-the-box and is ready to be installed (of course, like all other new flywheels it might not be a perfect balance as we would like). If a SERVICE flywheel can be balanced at the factory as a separate unit (i.e. without the rest of the reciprocating assembly), then it can be balanced in the field as a separate unit.

[Roger G.]

Re: 454 clutch balance

Being externally balanced my understanding is the flywheel cannot be neutral balanced, it is out of balance to a spec. The best a shop could do would be to balance the flywheel to some spec? This assumes the rest of the rotating assembly is also balanced to the same spec. I'm pretty sure it is, I had it balanced years ago when it was apart.

It seems you're suggesting the flywheel may not be on target as manufactured? A shop may fine tune the balance?

The pressure plate I'd assume should be neutral balanced not wanting to have the engine balance dependent on that particular pressure plate.

Question is do people often have these units tweaked or do most just bolt them on out of the box? I've never had a clutch balanced but am willing to listen and learn.

[Duke W.]

Re: 454 clutch balance

In order to balance a cruciform crankshaft V-8 you need to know the reciprocating mass. The rotating mass is 100 percent balanced, but if it is distributed equally along the crank axis there is a resultant primary rocking couple, which causes the engine to rock back and forth about a horizontal axis perpendicular to the center main bearing every engine revolution.

This couple can be balanced by moving some of the existing rotating balance mass to the ends of the crankshaft, which is why the end balance weights are large and there is no balance weight on the center crankshaft cheeks. This will balance out the rocking couple without effecting rotating balance. On a 454 there is insufficient clearance in the crankcase for larger end mass, so Chevrolet moved some of the balance mass to the damper and flywheel.

If the engine has been previously balanced in the field the owner should have been given balance data, which should include flywheel unbalance. If you don't have this data the only way to determine it accurately is to disassemble the engine and weight the pistons, rings and top and bottom of rods and rebalance the crank-damper-flywheel assembly.

In the absence of this data the best way to proceed is have an engine shop with precision balance equipment determine the unbalance of the current flywheel and then check the new flywheel and ensure that it has the exact same out of balance.

If the shop can bolt the new clutch assembly directly to the balance machine spindle, then it can be checked and adjusted as necessary for neutral balance, or it can be bolted to a known neutrally balance flywheel, and any unbalance can be corrected by adding mass to the clutch cover.

Why are you replacing the flywheel?

Duke

[Roger G.]

Re: 454 clutch balance

In order to balance a cruciform crankshaft V-8 you need to know the reciprocating mass. The rotating mass is 100 percent balanced, but if it is distributed equally along the crank axis there is a resultant primary rocking couple, which causes the engine to rock back and forth about a horizontal axis perpendicular to the center main bearing every engine revolution.

This couple can be balanced by moving some of the existing rotating balance mass to the ends of the crankshaft, which is why the end balance weights are large and there is no balance weight on the center crankshaft cheeks. This will balance out the rocking couple without effecting rotating balance. On a 454 there is insufficient clearance in the crankcase for larger end mass, so Chevrolet moved some of the balance mass to the damper and flywheel.

If the engine has been previously balanced in the field the owner should have been given balance data, which should include flywheel unbalance. If you don't have this data the only way to determine it accurately is to disassemble the engine and weight the pistons, rings and top and bottom of rods and rebalance the crank-damper-flywheel assembly.

In the absence of this data the best way to proceed is have an engine shop with precision balance equipment determine the unbalance of the current flywheel and then check the new flywheel and ensure that it has the exact same out of balance.

If the shop can bolt the new clutch assembly directly to the balance machine spindle, then it can be checked and adjusted as necessary for neutral balance, or it can be bolted to a known neutrally balance flywheel, and any unbalance can be corrected by adding mass to the clutch cover.

Why are you replacing the flywheel?

Duke

The flywheel has surface cracks which I was told cannot be removed completely. I preferred to go with a new one rather than take chances with the original.

The engine was balanced over 25 years ago when I had to buy a new crank and pistons. I don't think I have any balance data, I'll check to verify. Pretty sure I still have the receipts. It may be possible to bring both flywheels to a shop, see how much they differ.

[Duke W.]

Re: 454 clutch balance

I think you should get a second opinion on the flywheel. Small blue spots (sometimes called hard spots) and numerous short - no more than about one-half inch long - cracks are common on old flywheels, but that doesn't mean they are not serviceable.

Was clutch operation smooth before you took it apart? If so, the flywheel may be useable as is, but it should be checked for runout. You could also have it Magnaflux inspected to check for larger cranks. Any long ones that reach the ID or OD of the flywheel would make it non-serviceable.

Can you snap and post a couple of photos - one of the entire surface and a close-up of the worst area?

My flywheel was as I described and IIRC turning it .010" got rid of most of the surface anamolies.

I'm usually in favor of reworking original parts, if possible, as long as they are not known to be inherently weak and lack durability - like early small block conn. rods - before replacing them, even if it's more expensive.

OE gray and nodular iron flywheels are pretty robust.

Duke

[Roger G.]

Re: 454 clutch balance

The clutch chattered quite a bit before taking it apart.
This was why I took on this project.

As a matter of history, I am correcting some poor judgement on my part when I replaced the clutch 20 years ago but didn't have the flywheel resurfaced. A decision I've regretted. The clutch was replaced while doing a frame off refreshing, best way I can describe it. I never had the pressure plate balanced, never noticed any unusual vibrations.

I will try to snap some pictures soon, post them. Agree, I generally prefer to reuse original parts rather than take chances on replacements.

[Terry M.]

Re: 454 clutch balance

The PRODUCTION flywheel and rotating parts are manufactured to specifications that include weight; however, as a near-final assembly operation engines produced at both Tonawanda and Flint were hot-fired on natural gas. While rotating, balance measurements were made and final balance was achieved (to a closer spec than the individual parts were manufactured to) by adding or removing weight from either the harmonic damper and/or the flywheel. I remember being told what those balance specifications were, but I no longer (if I ever did) recall them. If y'all have a curiosity I will get up close and personal with some of my engine build documentation this evening or tomorrow evening and see what I can find to quantify the final balance operation.

It goes without saying, but I will anyway: any replacement of any of the rotating parts originally balanced as a unit will upset that PRODUCTION balance to a degree no one can determine without balancing the entire rotating assembly all over again. And that statement has nothing to do with whether an engine is designed to be externally balanced or internally balanced.

I have an image of Clint Eastwood in his younger Dirty Harry days: “I know what you're thinking, punk. You're thinking "did he fire six shots or only five?" Now to tell you the truth I forgot myself in all this excitement. But being this is a .44 Magnum, the most powerful handgun in the world and will blow you head clean off, you've gotta ask yourself a question: "Do I feel lucky?" Well, do ya, punk?"

Edit add: http://www.youtube.com/watch?v=8Xjr2hnOHiM

Enjoy your choice.

[Domenic T.]

Re: 454 clutch balance

Roger,
I can't post a pic with this computer but I resurface the cracks using a lathe which gives 0 runout. The back is also checked for run out before I start.
Once it is cleaned up I then put it on a crude aircraft wheel balancer that has precIsion bearings and 2 cones to perfectly center the fly wheel. Lead weights with magnets are then stuck to the light spots which untill the heavy spot does not roll to the bottom. I then drill out the heavy till the wheel is perfect. THEN reposition the wheel on the fixture to make sure it was done correctly. And has no heavy spots.
Once that is done I bolt the pressure plate on the flywheel and check the balance as an unit. I mark the pressure plate so it is installed in the same position that it was balanced on the flywheel.
I find that the pressure plate can be balanced by adding a washer to the light side or a slightly longer APPROVED grade 8 clutch bolt. I then do the other end ( harmic balancer) and they are the pain as many are not true and have to be turned down a bit before balancing starts.
All this is done on a known internally balanced engine to make sure the flywheel and balancer are right.
The balancer was made by Goodyear for 210 MPH tires. Some are small and spin up a storm. This works on aircraft props also. I've done this for years with 100% results.

Dom
Dom

[Joe L.]

Re: 454 clutch balance

Being externally balanced my understanding is the flywheel cannot be neutral balanced, it is out of balance to a spec. The best a shop could do would be to balance the flywheel to some spec? This assumes the rest of the rotating assembly is also balanced to the same spec. I'm pretty sure it is, I had it balanced years ago when it was apart.

It seems you're suggesting the flywheel may not be on target as manufactured? A shop may fine tune the balance?

The pressure plate I'd assume should be neutral balanced not wanting to have the engine balance dependent on that particular pressure plate.

Question is do people often have these units tweaked or do most just bolt them on out of the box? I've never had a clutch balanced but am willing to listen and learn.

Roger------


Flywheels are usually OK out-of-the-box. However, I like to have them checked and adjusted if necessary.

I have had GM pressure plate assemblies be considerably out of balance out-of-the-box. So, I definitely will always have them checked.

The whole purpose behind the above is to prevent "going back in" for a "do-over". I hate that. So, I'll do whatever I can to prevent it.

I think I can safely "guesstimate", though, that about 95% of flywheel and/or clutch replacements are done out-of-the-box with few problems.

[Roger G.]

Re: 454 clutch balance

Here are some pictures of the original flywheel.

[Joe L.]

Re: 454 clutch balance

Here are some pictures of the original flywheel.

Roger------


Actually, this flywheel does not look very bad, at all. I think it could be saved by re-surfacing. However, to be honest, I'm not a big fan of flywheel resurfacing. Among other reasons, removing any thickness from the flywheel weakens it and has an effect on clutch linkage geometry. The latter is quite critical on Corvettes. So, while this flywheel is very likely serviceable, I support you decision to go new.

[Duke W.]

Re: 454 clutch balance

Yes, I'd say that's typical for a flywheel with 100K miles. I don't think I've ever seen a spec on maximum material removal (like brake durms), but the biggest problem is that there might be runnout that is causing the chatter or it might be the pressure plate.

So, I'll again recommend that you take it to at least a couple of more machine shops and get their opinion. I turned my flywheel on the brake turning machine at the Air Force auto hobby shop.

Duke

[John H.]

Re: 454 clutch balance

Here are some pictures of the original flywheel.

Roger -Note that if you resurface a flywheel, it should be done on a double-acting orbital flywheel surface grinder, not on a lathe, to create the correct friction surface.


FlywheelFinish800.jpg

FlywheelSurfacing.jpg

[Domenic T.]

Re: 454 clutch balance

John,
I'm sure you are right, but as I do disc brake surfaces, I have had great results using the lathe. Reason for my decision was to check run out and keep balance. I used to send the flywheels out and they were not ground evenly. I am sure, with the right shop the grind would be good, but I did not find them true which does effect the balance.
I believe the acceptable run out is .001 or .0015 and most shops exceeded that. So having to chuck the flywheel up to check their work made me decided to cut them myself. Another shop here does them on a brake lathe like Duke said he did his. I can say that I saw a auto machine shop run heads and fly wheels over the rotating stone table, and that is bad at best. The table method was so bad that the heads would have more cut off one side than another depending on how the guy slid the head across the table.
Good machines, bad operators in most cases.

Dom