Balancer slides in on install

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the fitment method will take into account the harmonic frequencies that are being damped,across the rpm range between idle and redline.
they usually try to push the primary harmonic above readline with the mass of the damper and cater for secondary and tertiary harmonics in the operating range with the ring and rubber bonding.

those harmonics vary dramatically between the poorly balanced 4 cylinder (some of them need balance shafts as well) the nicely balanced 6 cylinder and the offbeat rumbling of a standard US V8.

i.e some work was done to establish the maximum damping achievable with the smallest mass at the smallest radius from crank centre with the available rubberised bonding material at the time. or indeed in some cases how much dense fluid can be contained in a sensibly sized outer ring.

The coupling between the damper and the crank can vary the effectiveness of the damper at different frequencies.

in some cases press fit will be a concern, i.e a decision was made that it should be press fit, and in others the frequencies dictate that a bolted on damper does the job perfectly well.

i think big block pontiac engines have 3 inch mains , thats one big fat crank in a big engine maybe the harmonics are small, maybe the crank and its interaction with all other connected parts has little vibration? dunno. either way they chose it to be slip on with bolt, it wasn't an accident. maybe that crank doesn't "buzz" like other cranks at a specific frequency so the damper in this case is potentially more about weight to counteract what is at the other end of the crank

i.e avoidance of the slowing down "spinning top" scenario that waggles the end you use to spin it, as the flywheel at the other ends slows.
saves main bearing cap no.1 from getting battered and stretched.
a crank that twists and flexes with each cylinder that fires may well vibrate in a different way, which may well dictate a different style of mounting i.e press fit

having a damper is better than not having one
having a damper mounted as intended is going to do the best job of damping

Dave
 
mshred said:
What exactly are you saying? Maybe I am misunderstanding, but I am also getting some numbers from elsewhere and I just want to find a decent range that hopefully lands me in the middle. I am also going to measure the inside of the balancer.
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Take these numbers given as examples with a grain of salt. The come from different measuring devices with probably questionable calibration (no offense intended). You need a proper size micrometer (not caliper) that discerns down to 0.0001" to accurately determine if your crank is in spec. A bore mic or bore gage would be used on the damper. Might be able to get away with snap gages, if you know how to use them.
The tools and methods used matter. A lot of folks that don't regularly work to thousandth or tenth of thousandth tolerances, don't understand that. Even leaving the mic out in a sunny spot on the workbench can cause enough thermal expansion to boof the reading and screw something up. You don't need a climate controlled clean room, but you do need consistency.
As to your damper, it was designed to be a press fit on this engine. The clamping area provided by the bolt against the small shoulder on the crank is tiny in comparison to the area covered by a proper press fit. It's an expensive risk to take doing it the wrong way.
 
AndyF said:
It is an interesting question and I don't know the answer. Some OEM engineers didn't think a press fit was a requirement, others did. A lot of Ford engines used a slip fit damper. It all worked okay for passenger car use. For a low budget rebuild on a passenger car engine I wouldn't be afraid of a slip fit. I'd rather not have a slip fit, but if it was my only option I'd take it.
For racing the recommendation is always use a slight press fit. Somewhere in the 0.0005 to 0.001 range depending on the size of the crank snout.
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This is the thing- nothing I can find says that it NEEDS to be a press fit as a requirement...Not saying that it isn't, but I can't seem to find any proof other then what we all generally would believe as a requirement. Even in the factory service manual, I can't find anything that would say that the damper needs to be a press fit or shouldn't be used if not, but then it also says to use an installer to get it on which would obviously suggest the balancer should be a press fit.
gzig5 said:
Take these numbers given as examples with a grain of salt. The come from different measuring devices with probably questionable calibration (no offense intended). You need a proper size micrometer (not caliper) that discerns down to 0.0001" to accurately determine if your crank is in spec. A bore mic or bore gage would be used on the damper. Might be able to get away with snap gages, if you know how to use them.
The tools and methods used matter. A lot of folks that don't regularly work to thousandth or tenth of thousandth tolerances, don't understand that. Even leaving the mic out in a sunny spot on the workbench can cause enough thermal expansion to boof the reading and screw something up. You don't need a climate controlled clean room, but you do need consistency.
As to your damper, it was designed to be a press fit on this engine. The clamping area provided by the bolt against the small shoulder on the crank is tiny in comparison to the area covered by a proper press fit. It's an expensive risk to take doing it the wrong way.
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Yes, this I understand. I don't even have a set of mics, and I forgot that my digital calipers went to s#$% the other week. I did get home and zip the balancer bolt off, and the balancer came out by hand with little effort. Needless to say I think my best option at this point is to check with another balancer and go from there.

I imagine if the crank was bad I would have noticed it somewhere possibly when checking bearing clearances. Even though I did not mic this crank, I did check the clearances with plastigauge on all the journals, and in different positions, and the readings were spot on almost across every main journal (and rod). So hopefully its a balancer replacement and done...I feel a little nervous to run it as is, especially since it just slid off by hand last night upon checking.
 
....and speaking about the Pontiac remarks, I've personally torn down probably four Pontiac V8 engines and they all had press fit balancers. For whatever that's worth.
 
RustyRatRod said:
....and speaking about the Pontiac remarks, I've personally torn down probably four Pontiac V8 engines and they all had press fit balancers. For whatever that's worth.
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My Dad and Brother built a pretty stout 488" stroker Pontiac for my brothers 71 Lemans a few years back, going to see if they remember what the balancer was like going off and the new one going on just for curiosity sake.
 
mshred said:
My Dad and Brother built a pretty stout 488" stroker Pontiac for my brothers 71 Lemans a few years back, going to see if they remember what the balancer was like going off and the new one going on just for curiosity sake.
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That's a good idea!
 
I will come back and say that I also cannot remember if those Poncho engines I worked on had stock balancers or not. Knowing who I did the work for, probably not. This has been over thirty years ago. I do agree with our friend down under that the stock Pontiac balancers are most if not all a slip fit. That does stand out in my mind so I imagine the ones I had experience with had some type of performance balancer.

All that said, think of it this way. If you want to silence a bell, do you very lightly put your hand on it, or do you grip the bell pretty firmly? Same principle. In order to absorb vibration "better" something needs to be a tight fit.
 
mshred said:
Yes, but I'm building a Mopar as we know, and its different lol...but will be interesting to see, as the whole build was pretty no expense spared.
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Good that'll mean it probably has an aftermarket balancer then. Please update this when you find out.
 
mshred said:
Working on a 70s 360, and upon putting it back together, the damper slid right over the snout of the crank by hand. I found this strange, as I did have to use a puller to remove it on tear down, albeit it came off super easy. Its a factory balancer, and it appears to be in good shape in terms of inner and outer pieces. Lubed it up good, slid it on, and torqued the balancer bolt to the 100ft/lb torque spec in my 1971 service manual.

The balancer has no play once tightened, and it is definitely on all the way. Just wondering if I should be concerned at all about this...should I up the torque on the bolt to be safe? This engine ran for a couple of months in my possession and had no vibrations or issues during that time, the rebuild was more of a freshen up and to install hotter cam, heads and intake while going over everything else.
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Do not play around with thread lockers or overtigtening it. Check if the keyway is not cracked. This happens often whne the female part is pressed on. A crack will allow the hole to expand and make the fit loose. If that is the case the whole assembly could fly apart. Try a good aftermarket balancer. appliedspeed.com
 
The factory Pontiac dampener on the V8 engine with a factory crank is a slide on fit. Period. Some after market cranks are slightly oversize on the crank snout such that the D no longer slides on. Same deal on aftermarket Ds, often will not slide on. I have lost count of how many Ds I have had to open up slightly so that they slide on.
 
A lot of discussion. I can add as a retired machinist and having built many Mopar’s of my own :

All dampers started with larger bore stepped to a smaller interference fit to finish off.

I never had to measure the bore but I can tell you even a same size bore is difficult to install. I would doubt there is a .001 (larger) press fit. More like .0005. That half 1000th makes a big difference. And I don’t think the entire shaft would be the same as I mentioned before that at first the damper starts easier.
 
Road Grabber said:
A lot of discussion. I can add as a retired machinist and having built many Mopar’s of my own :

All dampers started with larger bore stepped to a smaller interference fit to finish off.

I never had to measure the bore but I can tell you even a same size bore is difficult to install. I would doubt there is a .001 (larger) press fit. More like .0005. That half 1000th makes a big difference. And I don’t think the entire shaft would be the same as I mentioned before that at first the damper starts easier.
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Good point. If a damper is designed for a .0005-.0010 press fit and you have say .0015 that is between a 50-100% increase in press fit. That’s HUGE.

I remember when NHRA made the rule on aftermarket dampers. Moroso (and some others) came out with aluminum hubs. Those were crank and block killers. But others like the Fischer (which I think became Innovators West or at least that is the technology they used) and Fluidamper came out and they had CLEAR instructions to hone the damper to fit if it didn’t have the correct press fit.

If that wasn’t done and it was tight, the constant forces on the hub of the damper would cause a fracture to start in the key way. Once the fracture progressed the hub would lose its press fit and off they’d go.

At the 1988 or 1989 Seattle Nationals we watched a FD come off a Comp engine and it wasn’t pretty. Killed the engine and tore up the car. Someone could have gotten hurt. Bad.

The other side of that was about that time the Chinese cranks were starting to hit the market and crank snout tolerances were all over the place.

Some guys with brand new cranks and dampers ended up with a slip fit. Rather than addressing the issue, some guys were using red loctite.

The end result was a crank failure. The damper was basically just there for the ride and wasn’t doing anything. Next thing you know…zing…crap is flying everywhere.

I saw two specific cranks that failed from that. Both still had the crank snouts in them, held on by the bolt.

How many cranks and engines over the years have been junked and destroyed because damper fit was incorrect?
 
Just to update this thread, I ordered a basic Dampener from Summit crossing my fingers it would be a press fit and not a bad crank. Didn't have time for a full install, but yesterday went out to the garage quickly and tried to slide it on the crank snout- it slides on by hand the first bit, but will require an install tool to get it the rest of the way.

Verdict is, its not the crank that is bad, thank goodness. Old damper is going into the scrap pile.

Thanks for all the input here. I'm glad I asked and didn't just slap it together.
 
That's good news. Glad it worked out.

Having fixed "mistakes" in the metal shop I know just about anything can be repaired. Example they sleeve cylinders.

I could see how a rare damper such as six pack external balance damper could be repaired.

It's just metal. Bore it. Sleeve and weld into place to prevent rotation. Bore/hone to specs and keyway cut. Balance to specs. You would never know it with a good welding job.

It's a lot to do and simpler to buy another but I don't see why a damper could not be saved if push comes to shove.

Just throwing it out there.
 
mshred said:
Just to update this thread, I ordered a basic Dampener from Summit crossing my fingers it would be a press fit and not a bad crank. Didn't have time for a full install, but yesterday went out to the garage quickly and tried to slide it on the crank snout- it slides on by hand the first bit, but will require an install tool to get it the rest of the way.

Verdict is, its not the crank that is bad, thank goodness. Old damper is going into the scrap pile.

Thanks for all the input here. I'm glad I asked and didn't just slap it together.
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That's great! I'm glad you got it sorted out.
 
I've worked on many breeds, the Toyotas are slip fit cold, spin to chip 7500rpm, no drama, can't remember the Hondas.

Something you might be overlooking is expansion rates of different metals, clearance change with temp.
Valve settings as example, steel fluid transfer tubes into cast iron, no seal.
Food for thought .
That's why engineers get the big bucks,- us mechanics get nightmares and near impossible flat rates.
 
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