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Technical Cutting down a Damper?

Discussion in 'The Hokey Ass Message Board' started by chrisp, Feb 28, 2019.

  1. chrisp
    Joined: Jan 27, 2007
    Posts: 734

    chrisp
    Member

    I got a free engine that's missing some parts for a special I'm collecting parts for. Lucky me in the same family of engines a lot of parts are interchangeable except the harmonic balancer that are different in diameter and that part exists only as a reconditioning service for my engine, but you have to have one in the first place.
    So my question is : can I take a new repop damper for the bigger engine, turn it down to where it doesn't interfere with anything and have it rebalanced?
    I did try that on an old big damper (the machining part) and I don't hit the rubber with plenty of margin and it fits the crank like a glove, I just have to shim the pulley.
    Any thoughts?
     
  2. dana barlow
    Joined: May 30, 2006
    Posts: 3,388

    dana barlow
    Member
    from Miami Fla.

    What engine? Is it exturnely balanced* or not. SBC ,Chevys have a few sizes,the 400 was "X" and that's harder to get right*. For a zero balancer;The wt. the harmoric outer part of balancers is,just helps twist vibs,but can be cut down or even removed all together=if so ,it cuts down on how long the crank last with out starting to form cracks. There is not a really big time gap,between with an with out for just going to foodstore,but for racing it matters.
     
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  3. pitman
    Joined: May 14, 2006
    Posts: 4,608

    pitman
    Member
    from Hampsha

    Damping out the 'harmonics' is worth the trouble, esp. if you accumulate miles of run time. Believe Dana would know, about crank failures and service factors. Always ran one on my SBC's. Drag racing the sm.journal 327 never had an issue, believe it was the late 60's larger dia., had a forged crank.
     
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  4. Deuces
    Joined: Nov 3, 2009
    Posts: 16,932

    Deuces
    Member
    from Michigan

    8"x 2"?????
     
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  5. DDDenny
    Joined: Feb 6, 2015
    Posts: 11,485

    DDDenny
    Member
    from oregon

    Not knowing what you are working on I'll just throw this out in general terms.
    Whether you (anyone) want to call them vibration dampeners or harmonic dampeners; they are engineered specifically for a reason, granted some racing applications replace them with solid hubs but they don't see the miles and various conditions that street engines see.
    May work fine but who can say for sure in the long term what the outcome will be.
     
  6. David Chandler
    Joined: Jan 27, 2007
    Posts: 1,061

    David Chandler
    Member

    If it's a cast iron outer ring, be careful. They do fly apart unexpectedly. Balance would be critical, and you did mention rebalancing it.
     
  7. mohead1
    Joined: Jan 18, 2013
    Posts: 544

    mohead1
    Member

    Uh....f-ck no!! You want an exploding piece of cast tearing out the radiator fan and watnot? Get the right size

    Sent from my SM-G900V using Tapatalk
     
  8. Mike VV
    Joined: Sep 28, 2010
    Posts: 1,421

    Mike VV
    Member
    from SoCal

    What's the saying...penny wise, dollar foolish.
    Just get one that FITS the engine combination that you have.

    Would it be wise...just in case...as you are machining the ring, it cuts loose from the rubber, and put's a 3 lb./6" dia. hole in your chest..!

    Mike
     
  9. lippy
    Joined: Sep 27, 2006
    Posts: 3,935

    lippy
    Member
    from Ks

    I'm with the GET THE RIGHT ONE crowd. Lippy
     
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  10. Oldioron
    Joined: Dec 12, 2018
    Posts: 592

    Oldioron
    Member

    Yep what they are saying.
     
  11. chrisp
    Joined: Jan 27, 2007
    Posts: 734

    chrisp
    Member

    It's a Jag 2.4L L6, reproduction damper simply don't exists, they were 3 different types of damper on that engine, one of them had the pulley cast with it, which wouldn't work at all for my application and unfortunately it seems that it's the easy one to find used. It's not being penny wise it's just that I would need to get a $250 new cast damper for a 4.2L, cut it down then pay an other $60 to have it balanced, not the most economical way to do it.
    I know there is a small diameter aluminum one that exists from ATI that is a converted SBC . But there's a Brit who build Jag race engines who advise against it. Then there is the Pro Race aluminum one which is smaller in dia than the original one but bigger than the ATI and might interfere with the water pump by only a few mm, if I could get my hands on one to do a mockup I could see if I could cut down the water pump tab that's interfering.
    Now if you all advising me against cutting down a cast iron damper I won't do it.
    I just need to continue looking for the correct used damper to have it rebuild. I'd like it not to take years like it did on some parts for some of my builds.
     
  12. tb33anda3rd
    Joined: Oct 8, 2010
    Posts: 14,635

    tb33anda3rd
    ALLIANCE MEMBER
    1. Connecticut HAMB'ers

    can the pulley be machined off the common one?
     
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  13. oldolds
    Joined: Oct 18, 2010
    Posts: 2,682

    oldolds
    Member

    You need to get it rebuilt anyway? Turn a steel band down to the right size and sent it with the inner part.
     
  14. sunbeam
    Joined: Oct 22, 2010
    Posts: 3,975

    sunbeam
    Member

    I would look for a nuteral balancer damper that is the right diameter and a smaller shaft size and bore the center to fit.
     
  15. chrisp
    Joined: Jan 27, 2007
    Posts: 734

    chrisp
    Member

    I guess so but that's a lot of material to remove and this time really close to the rubber part then drill it to mount the pulley, not knowing if there is enough material for tapping.

    Knowing the rebuilder they might just say it's useless because it was modified. Plus I tend to be wary of remanufacturer who bond rubber to metal, I've seen rebuilt motor mounts on a oddball car debonding after a few miles and it was a 40hp engine...

    The center bore is a cone with a key, ATI use a chevy damper for the bigger Jag engines that might fit my engine, but Jag engine builders advise against it, is it because they don't want any popular brand on their high end cars?
     
  16. DDDenny
    Joined: Feb 6, 2015
    Posts: 11,485

    DDDenny
    Member
    from oregon

    There used to be a guy in Calif. years ago that fixed Jaguars by putting small block Chevy engines in them, it was called JTR, short for Jags That Run.
     
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  17. MAD MIKE
    Joined: Aug 1, 2009
    Posts: 317

    MAD MIKE
    Member
    from 94577

    Found this link;
    http://www.bobine.nl/jaguar/02-engine/crankshaft-damper-assemblies-for-xks/
    There are a few other dead '404' links, maybe the waybackmachine has those pages stored.
    From reading it seems these 'Metalastik' dampers are rebuildable.
    Or does no one actually offer this service?
    Which part number are you actually looking for?
    Im guessing C12037 is the one you need.
    Does he advise against ATI, or just the AL unit?
    I could understand not wanting to use the AL units on anything that is not a drag engine.
    Does the 3.8/4.2 ATI 916021(steel) not work for your application?
    I prefer ATI as they are tunable and can be rebuilt.
    Of course the biggest issue is maintaining the correct mass of the damper. Cast Iron is often used as it has more mass and a more compact damper can be built using Cast Iron. Steel dampers are much larger than cast iron due to the mass, or to at least match the mass of the Fe units.
    Yeah, spinning cast iron bits don't take well to modification.
    And unless you know the original mass, chopping down a different damper to fit may be as bad if not worse than simply leaving a damper off.
    Have you tried contacting Trelleborg/Metalastik to see if they have any information on where you might be able to purchase such a damper or equivalant. Might find an engineer that can help, never hurts to ask the OEM.
    I'm surprised that the Jaguar aftermarket, which seems to be fairly tight knit, doesn't offer such a basic component.
    Or is being on the Channel a bit of a shipping/import nightmare?

    Page 12 looks interesting...
    http://maybeme.com/Storage/x300/SNG_CatalogueEdition4.pdf
     
  18. chrisp
    Joined: Jan 27, 2007
    Posts: 734

    chrisp
    Member

    I don't know why he advises against the Chevy damper, he doesn't name ATI but they're the only one who make it.
    I checked the measurements of the ATI: it would still interfere with the water pump.
    I don't quite get the importance of the mass, I understand why it's there but about the mass being so relevant?
    4.2L damper 2.5kg (5.51lbs)
    3.8L and 3.4L damper 2.04kg (4.49lbs)
    2.4L damper 2.4kg (5.29lbs)
    ATI 2.8kg (6.25lbs)
    Pro Race 4.8kg (10.58lbs)
    the XJ6 that is a common replacement used for AC cars on 4.2L and 3.4L/3.8L is the same weight as the Pro Race
    Both ATI and Pro Race are said to be for the 3.4L, 3.8L and 4.2L engine. we're talking about at the worst a 135% increase in mass and at best a 9%...
    I have to check the weight of the one I machined down for mock up on monday.
    Once again the machining I did on that one is very far from the rubber about 1/2". I can't understand either how cutting a chamfer on the lathe on the damper would compromise it's integrity.
    Now I may have found a reman C12037 damper for a lil' over $500, compared to $250 for a brand new 4.2L one ... That makes me want to try to be penny wise :D
    They're no problems buying anything in any EU country, except language barrier sometimes.
    The problem of the 2.4L engine is that it's not popular and a lot have been discarded in favor of the 3.8L.
     
  19. saltracer219
    Joined: Sep 23, 2006
    Posts: 617

    saltracer219
    Member

    Damper Dudes in Anderson, Ca. you can google them for their phone number. I had a very rare 57 Chev 270 hp balancer rebuilt by them recently for a restoration project, they did an excellent job. They specialize in rebuilding all types of harmonic balancers.
     
  20. dan griffin
    Joined: Dec 25, 2009
    Posts: 417

    dan griffin
    Member

    Early Olds V8s did not have a harmonic balancer and they did not fall apart.
     
  21. Smart fellas there

    You could run a blower, the belt does the job
     
  22. metlmunchr
    Joined: Jan 16, 2010
    Posts: 721

    metlmunchr
    Member

    You can't just go by the weight of a damper in judging how it might work on a particular engine. You could cut one down to the point where it weighed the same as another one, and it might work or it might do nothing or it could even magnify the torsional vibration.

    Most 71 series Detroit diesels use a Fluidampr viscous damper. One of our 6-71s broke its crank going up a fairly gentle grade one day. In tearing down the engine, we found the damper's outer shell was somewhat loose on the hub. Pulled the pan off and found the crank broken at the #2 main journal. That's exactly where you'd expect the crank to break due to a bad damper.

    Its not something that's immediately obvious, but torsional vibration is most likely to break a crank near the end opposite the flywheel. The torsional stress on the crank isn't uniform from the nose end to the flywheel end. The further you progress along the crank, the more pistons you have putting power into the crank, and this works to create more and more torsional preload. But, there's nothing at the first cylinder to keep any preload on the crank, so each power stroke there is followed by an unloading of the torsional load. This cyclic loading and unloading causes fatigue which can lead to breakage over time. The main function of the damper is to counteract the vibration caused by these loading and unloading cycles, particularly at the natural frequency (harmonic) speeds where the torsional vibration can amplify itself to destructive levels.

    Harmonic dampers are engineered devices and not just some random glob of iron and rubber. To blindly modify or delete one isn't a smart move.
     
  23. Dyce
    Joined: Sep 12, 2006
    Posts: 1,761

    Dyce
    Member

    How about removing the rubber ring from your balancer and machining a new balancer that bolts to the flange or would fit between the flange and the pulley. A picture of what you have to work with would help.
     
  24. Desmodromic
    Joined: Sep 25, 2010
    Posts: 290

    Desmodromic
    Member

    I'm not really knowledgable on these engines; originally they were marketed as 2.4L, in the sixties, they were called 2.5L, and are maybe more common? Are these really the same engine, and do they have the same balancer? When the FIA rules on displacement changes, many race cars were built using the smaller engine, I don't know if these were based on sleeved "big blocks", or bored "small blocks". If you can find a way to contact some vintage racers that run the small engines maybe they could give you some guidance.

    Is there any chance that you could cut down the balancer as required, and make a new pulley that would have enough additional mass to correct for the loss? Or machine a new balancer with equivalent mass, but designed for the required clearances? Or, if the pulley is a "bolt on", make a steel ring that bolts on under the pulley bolts. (Technically, to get identical damping, you must match the rotational moment of inertia, which means the added mass should be at the same distance from the crank centerline as the removed mass.

    I'm aware of a couple of shops in the USA that are involved in Jaguar racing applications; if you'ld like, I can call them or provide contact info. But I assume there are many more such shops in England.

    I am curous what your application is. I have an old 2.4 engine with triple Webers, which I plan to put in a "new" vintage race car (tube frame, Devin body).

    EDITED UPDATE - I just looked at a cutaway drawing; the pulley is bolted to the crankshaft side of the balancer, not the isolated side. Therefore increasing the pulley mass will of course not work.
     
    Last edited: Mar 3, 2019
  25. MAD MIKE
    Joined: Aug 1, 2009
    Posts: 317

    MAD MIKE
    Member
    from 94577

    There are several brands that make aftermarket dampers for engines. Some are good(ATI) some I wouldn't tell my worst enemy about(various 'power pulley' brands).
    Unless he gives you a specific brand name and reason why he's against it, I would take that advice with a bit of sand.
    It's a tuned damper. It needs to be sized correctly for a given engine size and power band.
    http://www.atiracing.com/products/dampers/101/index.htm
    http://www.atiracing.com/products/dampers/damper_dinan.htm

    The outer ring is the mass damper. This ring is bonded to the crank hub of the damper via a rubber ring/band that allows the outer ring to resonate and absorb/dissipate the harmonics that would otherwise damage the crankshaft and other rotating components of the engine. You would need to know the mass/weight of the damper ring itself, and how much the elastomer allows the outer ring to move.

    Similar problem with modifying the damper, as with attempting to resurface a dual mass flywheel, you need to secure the component you are actually going to machine not the hub. That rubber ring will allow the outer ring to deflect which will not allow for concentric machining of the hub. This may cause the ring to be offset and become an unwanted counter-weight, which would increase bending loads on the snout. This would increase as rpms increase. Not good. And the outer ring, being made out of cast iron, may not do well in being machined. It may crack and eventually explode, taking out whatever other components may be around it and damage the vehicle.

    Might want to contact ATI and see how much they might charge for a custom 2.4 damper. Just because it is not listed on their site doesn't mean they haven't had one made before.
    There are several engines that did not come from the factory with a damper. Usually low rev, low power engines. Oldsmobile 260 and 307'Y' engines didn't have dampers, as their cast cranks(self dampening) and low rpm capabilities didn't require any additional dampening requirements. I wouldn't be surprised that their multi-belt setups probably also aided in some limited additional dampening.
     
  26. lippy
    Joined: Sep 27, 2006
    Posts: 3,935

    lippy
    Member
    from Ks

    Every higher revving engine can benefit from a damper. I believe a wore out old damper is at times worse than no damper. Mad mike I believe has it right. And I bet when you chuck that ring up and spin it you will be amazed what that center hub does. Since you have an engine that a damper is hard to find for, you are going to I bet have to spring for a custom one. ATI, or maybe , possibly our old friends in Salina Ks, Innovators West. Lippy
     
  27. Desmodromic
    Joined: Sep 25, 2010
    Posts: 290

    Desmodromic
    Member

    I emailed several USA vintage Jaguar parts suppliers regarding availability of the damper, without much luck. One suggested as follows:

    "The damper C12037 (2.4 Sedan, MK1) is no longer available, you could try Jaguar Heaven in Stockton, CA 800-969-4524 or Jagnut in VA 540-743-4037 for a used one."
     
  28. chrisp
    Joined: Jan 27, 2007
    Posts: 734

    chrisp
    Member

    Thank you all for the answers and leads, I'm waiting for some answers to requests I made via e-mail.
    To understand better what I'm dealing with here:
    [​IMG]
    The one with the pulley is the 2.4, the black one a reproduction 4.2 and the rusty one a 3.8.
    [​IMG]
    Now you can see the build in clearance for the water pump.

    I disassemble an old 4.2 and the 2.4 I have. the 2.4 mass is 0.950kg (2.10lbs) lighter than the 4.2, and no the mass are not interchangeable.
    [​IMG]
    How the 2.4 fit on the engine
    [​IMG]
    How the 4.2 interfere
    [​IMG]
    When I was talking about machining it down, it was like this : holding it by it's mass and cutting down the mass
    [​IMG]
    That would give me the clearance I need and the modified mass would be just around 200g (7OZ) heavier than the original 2.4 damper mass.
    [​IMG]

    Now you made it perfectly clear that modifying the cast iron damper is a really bad idea, potentially dangerous.
    But the reproduction damper like the black one in the picture is a steel damper, so as long as I stay away from the rubber and don't put too much heat in it during the machining to preserve the bond, is it ok?
    Because I'm not too optimistic, for example the question I asked ATI is unanswered for a week now...
     

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