Engine Vibration - Part II
 

The 455 for my Catalina was rebuilt last April to correct the flywheel imbalance caused by retarded machine shop staff and company. See thread: "Tale of two flywheels".

Swapped the cam, upgraded to roller rockers, Rhoads V-Pro lifters to correct some top end issues...still not sure about the Rhoads, but that's for another time.

New billet steel flywheel (zero balance), and a stock LUK clutch, which finally improved the clutch and shifting action.

The entire rotating assembly was balanced. The old Eagle crankshaft I bought in 2008 had to be switched over from external balance to fully internal (zero front and back), the flywheel was not touched and along for the ride, but the two-piece 60s style Butler harmonic balancer was tweaked with some very small amounts of weight removed.

The new cam was broke in and it was ready to go, but there was still a vibration present. Granted it was not like before with a whacked flywheel, this time it was more isolated to an RPM range of 3000 to 4000 with maximum vibes around 3300+/-. It can be felt not moving, in neutral with clutch pedal in or out. More pronounced under a load going through the gears. It's not a severe vibration, but you can feel it enough to raise some concern.

The original build of the engine c.2010 was zero vibration to 5000 RPM+. I can't figure out why it's not better than this. One thing that crossed my mind was that my engine guy said he only used on piston/rod assembly to establish the bob weight for balancing being that it was balanced before. Also, if you convert an external balanced crankshaft to fully internal what other effects can occur? I'm sure it's been done many times with no adverse effects.

I drove the car all last summer and it performed well overall. I haven't talked to my engine guy about the vibration issues yet, but before I do I'd like to have some things to consider or discuss as to why this is happening.

If I recall correct a Pontiac flywheel is something like a 6 ounce external balance. I’ve drilled out stock Pontiac flywheels and converted them to neutral balance. Normally you can even swap the ext and neutral flywheels out for each other and they won’t vibrate.

Do you have the Bob weight and weight numbers from the balancing? Which billet flywheel do you have?

Did you have it balanced with your damper/balancer?


:confused:

It was balanced with all parts. Damper, pulley, and flywheel. Eagle crank was converted from external to internal balance to work with a new internal balance flywheel, which is a RAM 1557 Billet Steel.

I don’t really see anything wrong with the rotating weight parts except it is missing the ring weights. That would add 30 to 35 grams to the rotating assembly. But looking at that sheet I assume the rings were already on the pistons though and were weighted together. Normally a 455 piston with the pin is 804 grams. For it to be 854 that sounds like the heavier 250 gram pin or it incudes the ring weights. 944 sounds like a stock rod with a bearing in it. Could be a SIR aftermarket rod too. They added 5 grams for oil, so I would expect the rings were already on the pistons. Could be they missed the targets a bit?

I would NEVER swap the ext and neutral flywheels/flexplates out for each other.

H.O. Racing on Balancing:

Refresh my memory, you purchased a neutral balanced SFI balancer?

The 1557 flywheel is a neutral balanced flywheel.

Refresh my memory on which trans?

What kind of bellhousing and was it indexed?

And fresh my memory if you tried it without the pulleys on?


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About all that can be done is to talk to the shop that did this. They may have you switch to a different dampener and see if the vibration is eliminated. Watch the belts to see if they whip at different RPMs. If they whip much your issue is probably up front at the dampener. If the belts do not whip across the full engines operation range the issue is probably on the back of the engine. Then the fun begins, you”ll end up systematically pulling the tranny off the back of the bell housing and starting it to eliminate the vibration coming from the tranny. Then removing the clutch to see if the vibration changes. Beyond that your switching flywheels, then if it isn’t found the engines ends up getting rebalanced. It is obvious then that the shop missed the target weights on the crank.

Neutral balance is neutral balance. If the balancer is SFI neutral balanced, the shop can't argue that it's the balancer. That's why I said get an new balancer, it will be a process of elimination, and the shop can't argue.

This is what, round 2 with that shop? Shop is a factor, you can't eliminate that yet, until you eliminate all other factors/potential causes.

What's the tolerance the shop uses to balance? 12% or more? Well know SFI balancers are in the 4-6% range. You start weighing bob weights and start rounding, those tolerances stack up.

Powerbond boasts they spin up to 21k rpm. What's the shop do, maybe 6k rpm? Ask. Tell them you are still have a problem, you bring up tolerances and they will know you are zeroing in on remaining factors, they may offer to redo the balancing. If they do, you know there's an issue there. (Jay touched on that w his post)

Think I mentioned in the other thread I usually provide the PP along with the flywheel and balancer when having balanced. It's good practice. If you didn't, ask if that's what is needed to get closer.

Aaaaand, that's why I mentioned in other threads, that sometimes it's better to buy a balanced rotating assembly from a known-good shop, it eliminate or at least improves your chances of a correctly balanced assembly.

Keep at it, you will get there. Hot rodding is an art, and school of hard knocks. Patience & persistence is a virtue.



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Hopefully they drilled on the dampener to be meticulous about making the Bulter 2 piece dampener exactly neutral balanced.

Depends which one. But SFI balancers have higher tolerances in general. Say yes to SFI balancers across the board.


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Is there is a SFI balancer that interchanges with a 67 and earlier 2 peice set that works well with the old style front cover?

This video by Steve Morris is very good for educating yourself before taking a rotating assembly in for balancing.

https://m.youtube.com/watch?v=hjmijD...UgdGVjaA%3D%3D

Since this was a rebalance, the rod and piston sets were just removed and weighed intact. Rods are stock Pontiac.

You do understand that the original external balanced Eagle crank was removed and rebalanced to full internal balancing to accept a new neutral balance flywheel, right? Maybe you're responding to a different comment.

The balancer that's currently on the engine is a Butler AAC 2pc Harmonic Balancer/Dampers, 59-67 Pontiac 6-Bolt, AAC-630155.

When they rebalanced the rotating assembly, the metal hub (not the dampener part) of the harmonic balancer was tweaked...some material was removed. I know that was not done with the original build/balancing in 2009, so why would they do that now? If the crank is now fully internal, what's up with the balancer assembly? Should work on any configuration of internal or external.

It has a Butler AAC 2pc Harmonic Balancer/Dampers, 59-67 Pontiac 6-Bolt, AAC-630155

The trans and bellhousing are a matched set M-20 with the 2.56 1st gear c.1965. Had shifting issues with other clutch sets, but the new LUK stock clutch set eliminated them.

Shortly after I got the car back last spring, I had to swap out the fan clutch. There was a temporary increased vibration coming from the fan since the brass bushing was missing. Took care of that with the new fan clutch. While apart, I ran the engine with no accessories, there was no change in the vibration pattern or intensity. Does not change with clutch pedal in or out in neutral.

The specific shop that balanced it last spring did not do the original balance in 2009. I learned that they farmed it out the balancing task to another local shop...I didn't know this until I asked about the bob wt card back in 2024 when all this went down. So now they do their own balancing, but I have no original documentation of the first balance, which sucks.

If I get a new balancer, I'd have to swap out the timing cover/water pump since it's '65 design....I think.

The only good reason to grind on the hub like described is to make it more perfectly neutral balanced. If someone ground on the hub to help balance the crank, that by definition is external balancing. External balancing would make the dampener only fit that rotating assembly.

I never send neutral balanced dampeners or flywheels in with rotating assemblies for balancing. I will balance those parts by themselves to make them more exactly nuetral balanced. I assume that is what the shop did. But you will have to ask them. All neutral balanced dampeners interchange in terms of balancing. Dampeners go bad sometimes, and can create vibrations.

Yes, they drilled into the hub, not the outer part where the dampening occurs.

Going to a 68-up balancer setup is the hot ticket, if you're not trying to be stock appearing, that's a great upgrade.

I think I remember comments about the fan clutch. Did you do the water pump at same time? A bad fan clutch can take out the pump bearing. Just a thought there, not related to the vibration (since you tried w no acc), just figured I'd mention it.

Glad the clutch swap was successful too...


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Yes i was responding to "Normally you can even swap the ext and neutral flywheels out for each other and they won’t vibrate." in posting #2.

I guess JAY S ment you can swap an ext flywheel with another ext flywheel and a neutral flywheel with another neutral flywheel. (I hope...) :-)

Yes that is how it is suppose to work.

I think the fan clutch bushing was only missing for a short while with minimal time on the parts...maybe an hour or less at normal driving. I got to swapping it out rightaway after the engine was done. Drove it all summer and no water pump issues.


I've been keeping the engine mostly stock appearing and was looking at what's available now. PRW makes an SFI18.1 for 67 and older that would bolt on with no other mods from what I can tell. ATI dampeners are really nice but would likely require other parts swapping (timing cover and water pump) and pulley alignment shimming. That's what I know so far.

So what's the factory external balance weight? Anyone know that? Guessing it's in the 5-10oz range? Some other brand engines I have heard 50oz thrown around, but that's from memory only.

Because of that, you never know how far out a balancer or flexplate/flywheel is, not only by tolerance, but potential box-swap situations.

The one balance shop I used to use suggested it at one time, and I've always included the balancer & flexplate/flywheel. They didn't charge extra for it so it was no big deal. That's all they did was balancing, pretty sure it was called Crankshaft Specialties, don't think it exists anymore tho...

If there's an SFi balancer made for the earlier engines, I would think it would be a good idea to use it over one that's not, even on a lower performance build, it would aid longevity I believe.


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My understanding is that the factory dampeners were neutral balanced and the low mass external balance that Pontiac used was only applied to the flywheel/flex plate.

Now the guy that worked the rotating mass did check the stock 2-piece Butler dampener and removed a very small amount of mass to make neutral. Do I know how he arrived at that? No. I would like to think that he neutral balanced each of the 3 major parts (dampener, crankshaft, and flywheel) independent of each other, then assemble to check the entire rotating mass, if that's really needed.

PRW makes a neutral balance SFI 18.1 dampener in their Pro Series that is 5.50" to fit the 59-67 timing cover and pulley offset. Eliminates swapping out other parts, which is preferred. ATI does not make the smaller diameter dampener, but they look like a sweet part.

https://www.prwpower.com/prw-pontiac...-2442101/p3104

Oh wow that does look nice! And it does state that it's neutral balance.

I honestly am not very familiar with pre-68 balancer setups, or if they were neutral balance from the factory.

The fact that the pulley is part of it makes me question the pulley though. Not sure if someone balancing the balancer/rotating assembly would include the pulley.

How does the pulley look, beat up, or holes wobbed out? Can you post a pic of the balancer? And maybe just the pulley?



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Just read the instructions for that PRW balancer, and this is the comment for the Pontiac one:

"Pontiac V8 Engines - All 1961 - ‘79 engines - 326, 350, 389, 400, 421, 428, 455
Note that for this damper to fit ‘61 to ‘68 engines, you must use a ‘69 or later model timing
chain cover, water pump, pulleys, and related components. These parts can be sourced
from a wrecking yard or from Year One (800-932-7663, www.yearone.com). Kauffman Racing
Equipment (www.MR-1.com) offers a high-quality ‘69 and later front aluminum timing cover
at a reasonable price, and a similar cover is available from Performance Years (performanceyears.com). These dampers, unlike some competitors, retain the original Pontiac accessory
pulley bolt pattern, allowing you to use your original stock pulleys if desired. The Pontiac
damper is a neutral balance model, essentially the same as those used on all various-sized
Pontiac engines from 1961 through 1979. Additionally, this damper includes a big block
Chevy accessory pulley bolt pattern. Some modifications to the pulley or damper hub may be
required to use BB Chevy pulleys."

Not sure what the benefit would be of going to that, you have to swap the cover, so you might as well go to a '68-up one, it's a one piece. Unless it has something to do with the crank snout?



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Thanks for pointing that out. The PDF appears to address all applications in the "Pro Series" which makes me skeptical about what's generally written about the Pontiac offerings. The '59-'67 factory dampers are 5.50" diameter. One of the PRW Pro Series dampers is also 5.50" and the other is 6.90". The 5.50" damper appears to have been made to specifically fit the early style cover with the timing marker closer to the crank. Why offer one in that size at all? Doesn't make any sense if it doesn't work with the older style cover. The 6.90" would fit '68 and newer style cover as the tech memo states.

I will call the tech help line and confirm.

I talked to the tech help at PRW and confirmed that the 5.50" dampener is specifically made for the early style timing cover. So if you want to upgrade, that's the ticket. A new pulley is included, however, this part does not have any degree markings on it, just the single line for TDC...BOOO! Alright so this is an good part for near stock applications. The larger 6.90" dampener would require the newer ('68 and up) timing cover and water pump, and it comes with the degree markings.

I don't know about pulley offsets differences between the 67 and older vs. 68 and newer, so that requires some research if a guy were to go that route. Maybe someone here can confirm.

Balancing of the rotating assembly shouldn't be that complicated. I've always thought that the more parts attached to the crank, the better the final result. For an internal balanced setup, if the crank is zero balanced by itself then you add a zero balance flywheel and a zero balance dampener, there will be no change in the result, just more mass rotating. When the guy last balanced it for this second go around, he included the flywheel and dampener (2-piece). He took a little mass out of the dampener hub. I don't think you should do that if it's already a zero balanced dampener. 0+0+0=0. Kind of pointless if you consider interchanging dampeners or flywheels. The crank by itself (with bob wts etc) is all that needs to be done. Of course if it's an external balance setup you do need all the attached parts, but that's not what I'm writing about.

So it's possible that Butler 2-piece is no longer zero balanced and could also be inadequate for the 455, therefore causing a narrow band torsional vibration.

Going to swap to a one piece damper. ATI 917160/161 @ ~$400 or Fluidamper 650401 @ ~$600. A '68 edelbrock timing cover and matching crank pulley for the 1-piece damper will complete the upgrade with no changes to the '65 bracket set. ATI damper requires drilling the pulley for 3-bolt. Not a big deal if that's what I choose.

I've provided a little interchange chart that demonstrates the parts you need to upgrade to a 1-piece.

You can consider a BHJ pulley, which is drilled for the factory 4 bolt pulley pattern. Nitemare Performance sells a version that they mill for the AC pulley if you are running that.

http://www.nitemareperformance.com/bhjbalancers.html