440 source SFI fluid Harmonic Damper

Well I have had a strange vibration in my Charger since building the 512 low deck, at about 2k & 3500, sometimes worse & other times just a little, been reading some post on hear about some Harmonic damper issues
, Dwayne from Porter Heads mentioned about one that the bolts on the engine kept getting loose & the damper was replaced & all the loosening bolts stopped,I dont know what brand that one was, SO, I bought a Power bond SFI damper, its like a different car now, smooth as can be, VERY happy, Thanks guys for the input on Moparts !!!!
Charlie

Chinese dampers(or rockers).......... not on anything I build.

Not a good place to scrimp.

Glad you made the switch and found it to be worthwhile.

Both of those are going to be hanging on the wall in my garage as a reminder to NOT by cheap junk!!!! I cant believe how much smoother the car is at ALL RPM's, it is amazing. now if the weather would get cooler I will go to the track & try to crack into the 10's

Sounds like yours was a vibration “inducer” rather than a vibration damper.

Truth LOL,

Not the first time I've heard of this type of issue. At least yours didn't come apart while the engine was on the dyno, like experienced by one person who posts on here occasionally.

...or come apart at the track like my Source damper did!

I have a new BHJ sfi, I think it weighs only like 6.5 lbs. USA.

Anyone seen these before ?

https://www.ebay.com.au/itm/180942334808

Please note: the SEMA damper standard (S.F.I. 18.1) does not rate a damper’s effectiveness, or certify that it works at all (let alone on a specific engine) - only that it didn’t explode during the test. Their interest is limited to safety and qualify control, not specific engineering results.
I couldn't even find a requirement as to how accurately it must fit the subject crank nose. If it goes on easily it won't work, but will fret the snout and damper ID.

One way to tell if it's working: it's hot after a run.

Over the years I've had 3 dampeners fail, and none of them were from 440 source. I just don't understand it. From what I read here, I just don't get it.

Popular mistake "I have a (fill in engine details), and I discovered that the damper ID and pulley alignment of a (fill in very different engine) is the same, so I bought one". My favorite: "I can't afford a good one for my 235" stovebolt (long, fragile, 4 main bearing, long stroke L6 crank) but the 283" V8 (short, rigid V8 crank) damper fits, so I installed it Tuesday - and so far it's great!".
GM made over 30 different SBC dampers, and none of them are used on any other engine.

I've used one BHJ damper and it slipped the outer ring after just a couple trips to the track on a mid 11 sec 440. BHJ fixed it, but offered no explanation or anything on the failure. I'll never use another one from them.

Every manufacturer makes a bad one from time to time. Your chances of getting another bad one from them are the same as your chances of getting a bad one from someone else.

Did anyone else read the Tom Lieb (Scat Crank) interview in Engine Builder where he talks about harmonic dampers and totally comes down on fluid dampers in general? He also has other things to say about dampers, it'd be interesting reading for some of you.

R.

I read what he said. I'd like to see the science he used to figure out what he said.

I've been using fluid dampers since about 1984ish and never had a failure. I kicked some rods out, but never broke a crank and I was using stock cranks.




EDIT: I just thought about it and it was 1988 when I bought my first Fluidamper. After a 20 minute talk with a moron from ATI I decided I wasn't buying anything from them.


Elastomer dampers have a relatively narrow range of effectiveness. When I called to order the ATI I gave him the bobweight and RPM I was shifting at and he said it didn't matter. So I asked him if the same damper works for a 1900 gram bobweight and shifting at 6800 or a 1685 gram bobweight shifting at 8500? He said it doesn't matter.

While I agree w/ you, it still leaves one heck of a bad impression. I won't take the chance again.

Elastomer dampers have a relatively narrow range of effectiveness. When I called to order the ATI I gave him the bobweight and RPM I was shifting at and he said it didn't matter. So I asked him if the same damper works for a 1900 gram bobweight and shifting at 6800 or a 1685 gram bobweight shifting at 8500? He said it doesn't matter.

I don't have any data for your engine, but what he said might be true (if explained very badly).
The harmonic orders' RPM (sensitive points in the RPM range) are generally a function of crank length, stroke length, journal overlap, and weight - but not balance details. Which orders are dangerous includes engine design (firing order, L or V, number of cylinders).
Factors that make the crank stiffer (shorter stroke, more overlap, shorter OAL) tend to make all the orders occur at higher RPM.
The engine speeds for these orders can be calculated from the resonant frequency, where “Hz” is the crankshaft’s resonant frequency, and N is the order number, using this formula:
RPM = Hz × 60 ÷ N
A V8 crank may be 300 Hz (he may have a chart that shows this - did he ask your stroke length and journal diameters?), giving RPM points at
1st 18,000 RPM
2nd 9,000
3rd 6,000
4th 4,500
5th 3,600, etc.
Note that the area between 2nd and 3rd spans the entire RPM range 6-9,000, meaning the same damper is correct for any RPM in that range. The ones above and below it may be either irrelevant or too small in amplitude to matter.
My project 235" L6, 3.94" stroke, 2.68" mains, 2.31" rods for 216 Hz will have destructive orders at 2,160, 4,320, 5.184, 6,480, and 12,960 RPM - very different even from another L6.

Madscientist, I had exactly the same questions about the fluid dampers and Lieb's ideas.

Poly, that's a very interesting look at harmonics. I agree that bobweight will change the amplitude of the vibrations but not their frequency, which I believe is due to the physical dimensions and material of the crank.

Here's a question for you - Given that gray cast iron has a modulus of elasticity of 20EE6, while nodular cast iron and steel are right around 30EE6, does the material have an effect on the resonant frequency or just the amplitude?

R.

I love the math and the explanation. No, the dude from ATI didn't get in detail anywhere near that level. All he asked was what the actual bore and stroke were. He didn't care what RPM I shifted at.

At that time, I had a room mate who was big on ATI dampers (because almost everyone and their mother was using them) and I told him what happened. I kept a record of all my phone calls so I had the name of the guy I talked to. My roommate decided to them, talk to the same guy and see if he got a different answer.

He called and said he was running a low 11 second 340 and was going to up the compression and switch to a roller and dip it into the 10's and didn't want to use an OE damper. They gave him the exact same part number damper. Didn't ask what RPM he used or anything else.

He was dumbfounded. I don't know what else to say. It didn't make sense to me at the time, and still doesn't today.

It would be interesting to do the same thing today with the same RPM 340 and see what you get if you call back and see what they say about a 408 turning say 7000.

You can do the math and see if the overlap.