# Need your opinion on machined flywheel.



## RMTZ67 (Mar 12, 2011)

Ok where do I start. After searching for a affordable flywheel that was correct (got home with a napa flywheel that was to small) or having to drill out flywheel holes to get them all to fit (summit). So I took my decent original flywheel with minimal, hardly visible cracks to get milled. When I picked it up they told me it might need a .025 shim. I asked if they were gonna supply that and they said I should go elsewhere for it. So I explained pontiac parts are not nearly as easy to aquire as chevy and at what cost? So i mentioned I would not be taking it until I did some research on the shim and cost. Let me mention my uncle used to work there more than 10 yrs ago and has since retired but goes back every now and then to do something special I guess??? Anyway, they finally told me to take it at no cost. when I got home I noticed the gouge. Questions are, 1)Do you think I need a shim? 2) Will that gouge affect my balance much? Any input welcome.


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## PontiacJim (Dec 29, 2012)

RMTZ67 said:


> Ok where do I start. After searching for a affordable flywheel that was correct (got home with a napa flywheel that was to small) or having to drill out flywheel holes to get them all to fit (summit). So I took my decent original flywheel with minimal, hardly visible cracks to get milled. When I picked it up they told me it might need a .025 shim. I asked if they were gonna supply that and they said I should go elsewhere for it. So I explained pontiac parts are not nearly as easy to aquire as chevy and at what cost? So i mentioned I would not be taking it until I did some research on the shim and cost. Let me mention my uncle used to work there more than 10 yrs ago and has since retired but goes back every now and then to do something special I guess??? Anyway, they finally told me to take it at no cost. when I got home I noticed the gouge. Questions are, 1)Do you think I need a shim? 2) Will that gouge affect my balance much? Any input welcome.



Never heard of a shim. Have had a number of flywheels resurfaced. Installed them as was. Do not know the purpose of the shim?

I can't say if the gouge will affect the balance or not. I know with some flywheels that sometimes a simple couple of drill points are enough to bring the flywheel into balance.

Many of the aftermarket type flywheels are "zero" or "neutral" balanced. Pontiac uses the harmonic balancer and flywheel to balance the engine - which is matched/balanced to work with the factory parts. Using an aftermarket flywheel can throw off the balance because the flywheel needs to be balanced to match the needs of the factory piece. If you do not get an aftermarket flywheel balanced, you will experience some vibration - ask me how I know.

I had my brother's Mopar 360 engine assembly balanced. Typically, Mopar uses the torque converter fitted with a welded weight, along with the harmonic balancer to balance their engine. I decided to use an after market flexplate and used this to balance the engine. In doing this, I was able to use a "neutral" balanced torque converter having no balance weights. The reason was that if a different torque converter was chosen or if it needed to be replaced at some point, I did not have to worry about getting the balance correct on the torque converter after the engine had been assembled.

Fast forward to last year when he added a 4-speed. He did not take into consideration that the flywheel he got with the swap kit was intended for a factory balanced assembly. The engine was built and balanced with the aftermarket flexplate and the rest of the rotating assembly which was by no means factory stock anymore. Engine vibrates very noticeable now.

I mentioned this to my machinist. He said what needs to be done to correct this is to take the automatic flexplate and the flywheel to a shop that does balancing and have them balance the flywheel to that of the flexplate - which should bring the engine back into balance. If the unbalance continues, it will eventually do damage to the bearings and could even lead to engine damage.

So I mention all this not to scare, but to inform you so as you can decide what you may want to do. Personally, I might go to another shop and ask them for a second opinion and let them look at the flywheel. They would probably give you a more informed opinion than you might get from us. :thumbsup:


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## RMTZ67 (Mar 12, 2011)

PontiacJim said:


> Never heard of a shim. Have had a number of flywheels resurfaced. Installed them as was. Do not know the purpose of the shim?
> 
> I can't say if the gouge will affect the balance or not. I know with some flywheels that sometimes a simple couple of drill points are enough to bring the flywheel into balance.
> 
> ...


 I had the internals balanced at the machine shop and thought my flywheel (pontiac)was neutral balanced. Thinking neutral balance does not affect the internals. I also ordered the front crank balancer from butler. Wonder where the balance stands there? I believe the machine shop took a reading on the flywheel before and a shim (I am guessing now) brings it back to where it was?? They told me they have no specs on something this old. I showed the beveled edge because someone on another post commented how it was close to its max mill by looking at that edge.


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## PontiacJim (Dec 29, 2012)

RMTZ67 said:


> I had the internals balanced at the machine shop and thought my flywheel (pontiac)was neutral balanced. Thinking neutral balance does not affect the internals. I also ordered the front crank balancer from butler. Wonder where the balance stands there? I believe the machine shop took a reading on the flywheel before and a shim (I am guessing now) brings it back to where it was?? They told me they have no specs on something this old. I showed the beveled edge because someone on another post commented how it was close to its max mill by looking at that edge.



Hmmm. I am definitely not an expert on this and know that peoples comments can insite fear into any engine build as we want to get it right and not have any major disaster.

OK, further research on Pontiac harmonic balancers say you should be OK with the engine internals balanced as an assembly and then going with a neutral balance flywheel. The harmonic balancer according to a Hot Rod article states, 

"For many other makes, the hub contains a slight imbalance that is used to finely balance the entire reciprocating assembly, hence the name harmonic balancer. That isn’t always the case with the Pontiac V-8, however. Besides original 265/301 units, *Pontiac hubs were neutral balanced, serving no balancing purpose.* Vintage Pontiac literature refers to it as a harmonic damper, and for the sake of accuracy in this article, we’ll refer to it as such. Be sure the aftermarket damper you’re considering for your Pontiac is internally balanced."

That said, you can go with a neutral balance flywheel. I do not know if the factory flywheel is neutral balanced to match the neutral balance harmonic damper, but assume it to be based on the article. I know in my past, with factory engines, it was no problem to slap a different Pontiac factory flywheel from one engine to another or swap from an automatic to a 4-speed. 

It may be when we rebuild our engines and use other than factory parts that the damper/flywheel/flex plate can be used in the balance of the engine. It may simply be a cost effective measure to do it this way as when you balance an engine internally, it may require adding/welding a heavy metal called "mallory" onto the crankshaft and from my understanding can be costly depending on how out of balance the assembly is. My machinist subs out his balancing to a shop that specializes in this and the engines I have had him balance, he always includes the harmonic balancer and flywheel/flex plate as part of that process.

So, what it appears you want is to have a neutral balance flywheel. I do not know what the minimum thickness is of a flywheel before it cannot be resurfaced any more. I really am not a fan of cast iron flywheels for a HP engine if you can avoid it. Certainly the factory had no issues using them. A steel flywheel is of course an added expense and like most, we all have budgets.

Going with an aftermarket steel flywheel can be a better choice and you can go with a larger clutch set-up. Most are drilled for both the 10 1/2" disc and 11" disc. The more disc surface area you can fit, the more the clutch will grip. I have the Hays steel flywheel, neutral balanced. I am actually using a McLeod 12" set-up which bolts up to the bolt holes for an 11" clutch assembly. Single disc, but more surface area to really grab. First time using this, so hopefully it will work great.

You might still want to drop the flywheel off with your machine shop and let them check it for neutral balance - just for piece of mind and so you can sleep at night. :yesnod: From my experience, when you rebuild an engine and as you hit the road with it, you become extremely sensitive to EVERY little vibration, whir, change in pitch, creek, and any other noise you hear or even imagine coming from under the hood. Seems you don't have quite these concerns when you buy a car and run the engine that already has miles on it - you just shrug it off and figure if its going to blow up, then let it. Not so with that new engine build. :lol: So I would drop off the flywheel just for that reason alone. 

Don't know if you are a Clint Eastwood fan, but it is just like the movie Dirty Harry when he has the criminal under the barrel of his .357 and attempts to reason with the criminal as to whether he fired 5 shots or 6 because in all the confusion, he had forgotten. With the barrel of that big gun staring the criminal in the face, the criminal gives up the fight. But after he does, he looks at Clint Eastwood and says, " I just gotta know." Clint pulls the trigger and the gun goes click. :thumbsup:


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## geeteeohguy (Feb 2, 2008)

I would: have the flywheel checked and adjusted for neutral balance as Jim said and then I would bolt it up the car with no worries and run it. Much better than Chinese iron. No need for a shim....the clutch and pressure plate have plenty of movement to accommodate minor variations in flywheel thickness. I've been at this 40 years....Jim a touch longer. Never used a flywheel shim in all that time.


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## RMTZ67 (Mar 12, 2011)

Well here is the results of the balance on my flywheel and pressure plate. Not sure what to make of the weight on the luk pressure plate. Seems significant. The luk pressure plate I removed which I had installed 10 yrs ago said, made in the USA. The new one. Not so much. Wish me luck.


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## PontiacJim (Dec 29, 2012)

RMTZ67 said:


> Well here is the results of the balance on my flywheel and pressure plate. Not sure what to make of the weight on the luk pressure plate. Seems significant. The luk pressure plate I removed which I had installed 10 yrs ago said, made in the USA. The new one. Not so much. Wish me luck.


Very good, glad you decided to get it checked and balanced. As you can see, it did indeed need a little work. I have seen a section of a threaded bolt welded to a pressure plate cover - just how they do things. Drilling into the flywheel removes weight as needed to get it balanced. And, if the flywheel was not in spec as far as thickness, I am sure those guys would have let you know. Looks great. :yesnod:


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