Technical Harmonic Balancer Fluidamper type

I'm putting ........make that attempting to put together a combination for an 8-71 Blown Cadillac engine. I'm currently looking at options for the pulley set up. The crank hub I purchased from Blower Drive Service for a Cad came with a bolt pattern for a Chrysler V8. I know nothing about interchangability of Mopar stuff. I gather that the 6 bolt Chrysler pattern was "adopted"(?) as the standard pattern for blower pullies. Is that correct ?
So I prefer to run a harmonic balancer with the blower. Some people say no damper is needed, but I tend to think that it may prevent a problem. They use them on Diesels and the Cad will be a high torque but not excessive rpm combination. Parts availability and costs make this somewhat challenging.
I have some ideas to help save some length for the engine. The OEM version of the Cad came with a very heavy hub and no damper for a few years and later it had a balancer mounted inside the pulley apparently. Its actually kind of small for such a large (500 ci) engine. I'd like to use a balancer and locate it inside the engines crank pulley since I will need a spacer of some type anyway......if this works.
So in my comparative search for a suitable damper I honed in on the Fluidamper as the most desirable choice. ATI is still getting a look as well. Since it has a Chrysler pattern on the hub, the 7" Chrysler version is what I'm looking at. Not cheap at $533 from Summit.
Looked at several other sources and on Ebay I saw a brand called "Speedmaster"....not to be confused with the company (Speedway) that sells hot rod parts. Says their fluid damper is SFI certified and that they are a world wide company with locations in the US, Australia, and I forgot where else. They are way less expensive than the two I'm familiar with.
Anybody have any knowledge or experience with them ? What about my Aussie mates, do you guys use them?

www.ebay.com/itm/185149420401?_trkparms=amclksrc%3DITM%26aid%3D777008%26algo%3DPERSONAL.TOPIC%26ao%3D1%26asc%3D20230811123856%26meid%3D39db62d70dd947ac96351a6584fbf9e9%26pid%3D101770%26rk%3D1%26rkt%3D1%26itm%3D185149420401%26pmt%3D1%26noa%3D1%26pg%3D4375194%26algv%3DRecentlyViewedItemsV2%26brand%3DSpeedmaster&_trksid=p4375194.c101770.m146925&_trkparms=parentrq%3A49fe31e318b0aab324d5a8c8fffff6ec%7Cpageci%3A6d12db35-6ecc-11ee-9208-5a94751a71f8%7Ciid%3A1%7Cvlpname%3Avlp_homepage

 

I think dampers are tuned to a particular engine, or at least to a group of engines like the large journal 327 or 350. The 360 Mopar Fluidamper gets your pulley mounted but might it hurt a 500” Caddy? Would you be better off with just a steel hub? Lots to consider on this one, and honestly I’m just making a supposition here, I don’t have any direct knowledge.

 

See my avatar? Same engine you're using (but N/A). Ran it 6500 rpm for hundreds of passes in the 9.50-10.30 range. A fair number at the HAMB drags too! No damper, just the hub with pulley.
The cranks are heavy and quite strong, and it was the Early engines that had a small damper behind the pulley...later ones had only a heavy pulley.
In addition, the blower belt should act as a decent damper anyway.
If you really want a good damper you might search for Innovator's West in Salina,KS. They make 'em. $$

Terry

 

over 100k miles on blower motors...no damper...just a steel hub. It works.

The 6 bolt Mopar pattern is kind of the defacto standard, but they use 3/8" bolts instead of the Mopar 5/16

 

If I was that concerned I would talk to ATI and have them build me one.

 

Second vote for ATI, fluidampers are banned from use in nascar for good reason, when the fluid gels up and becomes a counterweight, its game over...

 

And no way to know if it has gone bad. The ATI can be rebuilt or adjusted if needed.

 

BHJ dampners are a good choice.

 

The blower belt acts as the dampener,,,,,,it absorbs the harmonics,,,,,,and dampens the pressures .
The middle on a harmonic dampener is made of elastomer rubber and retains the outer ring to the hub .
That’s all it does,,,,,,and the rubber belt acts as that go between on a blower drive hub .
It works,,,,Simple as that .

Tommy

 

I wanted to do a blown Cad 500 for my Stude way back when, but the intake manifold was a huge problem ($$$), so I built a much cheaper BBC.
This roots harmonics concept took me a while to understand, but I get it. Roots blown motors can get away without a crank mounted damper because the belt transfers harmonics to those heavy spinning rotors. Rotors want to stay spinning at a smooth speed. The belt can cancel out any forward/backward vibration or harmonic frequencies, because it is tied to those whirling rotors.
I've built 3 roots engines, the second one a 454 with a Fluidampr, before I figured this stuff out, and the third one, my 426 Hemi, with just a hub. Both worked the same, and bearing/crank life was good. BTW, the Fluidampr is still in action, with about 10,000 miles on the clock. As far as that simple old hub, it's one rare situation where the cheap alternative is a good alternative. Speedmaster = Chinesium labor.....
I wish you luck, you'll have something unique!

 

30k miles on rod bearings without a damper, but with a blower. The crank hasn't broken yet, either. This is in a 427.

 

I did talk with ATI, and basically they told me I'd need to order 10 of them to pay for the R&D on them.

I do agree with those of you that mentioned balancers being engine specific. The thing that sticks in my mind is that an OEM balancer is for a specific rpm range ......and all the rotating assemblies are essentially the same within production tolerances. Move to the aftermarket and to viscous style dampers and they are made for a specific engine.
The engines that they get mounted on have a large range of components in them from aftermarket manufacturers.
Different crankshafts made from different alloys are used. That changes where the harmonics may become a problem.
My basic understanding is that harmonics become a problem when you have two different sources in the engine and they are "complimentary". Each plays off the other and amplifies toward disaster. Two harmonics that are not complimentary usually help limit each other. (Thats all I know).
So when someone assembles an engine and puts an aftermarket forged steel crank in to replace a shorter stroke cast iron crank......the point where the harmonics play should change..........yet we install OEM balancers on them and they don't seem to be a problem. Add to that changing other components which have different harmonic traits and its a crapshoot at best (IMHO) no matter which engine the balancer is for.

I'm not adverse to running a heavy pulley and no balancer with a blower. I plan to build 2 engines. One with a blower and one without. They will have non-traditional fueling and ignition. (Let the booing begin) The idea is to use the non blown engine as a learning tool.....and an engine for a subsequent project. Then finish the blown engine and install it in my 32. I will need some type of spacer or possibly machine my own pulleys as it looks now. If I have to use a spacer, I'd like to incorporate a harmonic balancer in that space. I figure any additional damping can't hurt even if its not perfectly tuned for my engine. I may end up taking Jim's suggestion though. (Jim appreciate your pics) Right now my brain is going back and forth on how to do it, so all information and suggestions are appreciated.

 

Just thinking out loud here.....since the hub has the Mopar bolt pattern, is the crank snout similar in dimension to the Mopar (1.54") so that an oem dampener could be used? Good aftermarket options and gives you the spacer you need assuming depth is within range.

 

almost right. A crankshaft has a single dominant resonant frequency, and multipuls which are the harminics. All cranks have a resonant frequency, the problem is if its in the running range.

A rubber eliment damper introduces another resonant frequency that splits the dominant resonance into two much smaller resonances that are less harmful. The tuning is required to match the two frequencies to to split the peaks as much as possible and counterphase the resonances.. This is done by changing the rubber compound and inertia ring on the damper

Speaking as a former application engineer for a crankshaft damper OEM

 

I have two different situations for 2 engines. One blown and one naturally aspirated. I purchased a steel hub for the blown motor. It has dual keyways so have to have one added to the crank. The inside diameter is 1.5 inches to slip on the crank. It has a concentric shoulder on the front to mount pulleys or damper that is 2.0 inches in diameter. The bolt pattern is the 6 bolt Chrysler (which is standard for most blower drives ).

On the naturally aspirated engine I will probably use the OEM hub and machine it to accept something. Is the 1.54 diameter common to both big block and small block Mopars ........and Hemi's ?

 

Yes, common number for just about all Mopes, early and late. Keep in mind that MaMopar made a slight change in the bolt pattern in '62 and I expect that the hub will have the late pattern.

Adding a second keyway to the crank takes a very good machinist to match the hub.

 

FYI...If you measure the OEM Cadillac hub or the crankshaft areas where the hub presses on you'll find that there are two areas of press fit. They are NOT the same diameter. It's weird, but you'll find a few thou difference. Keep that in mind when modifying hubs or fitting other hubs to the crank. When I was running mine, I honed both areas for a light press fit...the stock press is VERY tight. Never had any problems.

Terry