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?


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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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