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Dodge 270 Hemi vibration

Discussion in 'The Hokey Ass Message Board' started by da dodge brother, Mar 17, 2011.

  1. da dodge brother
    Joined: Apr 2, 2010
    Posts: 386

    da dodge brother
    Member
    from wisconsin

    Now this might get a little long so bear with me on this. Some years back I purchashed a 1955 Dodge with the 270 Hemi. It was a fairly low milage car, 36,000, but I figured to freshen it up anyway. Opened it up and things looked pretty good. No problems at all. But to be safe we did a .010 on the crank and a bore job just to true thing up. From there on it was all the normal stuff, rings, bearings, valve job, etc. Now this was never intended to be a stock vehicle so we updated the drive train with a 1985 Mopar rear and a 904 trans. The adapter was from Wilcap. Got everything buttoned up and on the road. VIBRATION?? Checked everything out. found absolutely NO obvious problems. Now to explain this point. This vibration comes on with the car in NUETRAL or PARK. It does not have to be in motion. After checking things through we decided to tear it down and go through it again. This time we did a complete balance job, bought a special harmonic balancer from Hot Heads Hemi, went through all the componenets again and this time backed it up with a brand new 727 tranny with overdrive. Also installed a new torque converter from a 318 mopar. The engine was now internally balanced and this model converter has no balance weights on it. On the road again and the vibration is still there. All you have to do is bring the idle up to about 1150 and it starts to come on. It never really gets to be a real bad vibration but it one of those seat of the pants feel. You know just when you 40 MPH. Now I have put many miles on it with this problem and have driven it 70 - 75 mph. on the highway on long trips. So far no problems but that vibration is there. Checked everything underneath to see if the exhaust was rubbing or anything. No problems there. Any ideas are more than welcome. So far this vibration has not caused any problems but you get the feeling that eventually it will. Thanks for any suggestions...[​IMG][​IMG][​IMG]
     
  2. shmoozo
    Joined: Aug 14, 2007
    Posts: 672

    shmoozo
    Member
    from Media, PA

    My first thought (which may not be a good one, but I'll offer it anyway) is that perhaps something inside the engine isn't balanced properly. Maybe the pistons or rods aren't all the same weights or something.

    But wait to see what others offer as suggestions and thoughts before tearing it all apart to weigh the engine's internals to see if that's it.
     
  3. da dodge brother
    Joined: Apr 2, 2010
    Posts: 386

    da dodge brother
    Member
    from wisconsin

    I thought of that but here's the crazy point. That vibration seems to be the same now as it was before the balance job. I did forget to mention that it is a harmonic type of vibration not a steady teeth shattering type.
     
  4. Andy
    Joined: Nov 17, 2002
    Posts: 4,692

    Andy
    Member

    Maybe something with the water pump or gen/alt. Might remove the belt and see if better.
     

  5. 73RR
    Joined: Jan 29, 2007
    Posts: 6,545

    73RR
    Member

    Some 'zero' balance converters actually have weights on them to get to 'zero'...
    I'd be looking at the converter.

    .
     
  6. da dodge brother
    Joined: Apr 2, 2010
    Posts: 386

    da dodge brother
    Member
    from wisconsin

    Thanks for the tips. Here's where we're at. Removed all belts from water pump, alternater, etc. No difference. Had a stock dual point set up. Thought maybe some misfiring between the points or just plain old distributor. Replaced that with a electronic distributor setup. Now don't go thinking I'm just plain nuts here but this vibration is the same as when I had the old 904 trans. in with the other torque converter. But that was before the balance job. Now after the balance job I have a new 727 trans. w/overdrive and a different torque converter and same vibration. And like I said, it's a harmonic vibration, not a steady pounding type. One other thing. It changes as the engine warms up. It's worse when cold at start up and as the engine warms up to operating temp. the vibration lessons but is still there...
     
  7. 1948plymouth
    Joined: Feb 22, 2011
    Posts: 109

    1948plymouth
    Member
    from Minnesota

    Are the motor and trans mounts in really good shape?
     
  8. Andy
    Joined: Nov 17, 2002
    Posts: 4,692

    Andy
    Member

    dead cylinder? Pull plug wires one at a time and see if pulling one makes no difference. Maybe a bad cam?
     
  9. desocoupe
    Joined: Apr 22, 2010
    Posts: 31

    desocoupe
    Member
    from iowa

    I agree check the mounts it almost sounds like something isnt tight or the bushings are bad.Could it be a rocker/valve/ lifter vibration? I take it the engine doesnt miss,or anything out of the ordinary, some times the simplest stuff we overlook is the problem. Having the problem in park and not at idle is a real pisser. I look forward to the answer it sounds like my luck.
     
  10. These are tough, but with a little time it can be worked out.
    1. harmonic balancer - have you checked the index to TDC AND comparied it to another one
    2. flex plate- was it on the crank when it was balanced, have you checked it for cracks.
    Since you have changed converters and the vibration is in neutral and park it is somewhere in or on the engine.
     
  11. da dodge brother
    Joined: Apr 2, 2010
    Posts: 386

    da dodge brother
    Member
    from wisconsin

    OK - All new front engine motor mount and all new tranny mounts. Engine purrs like a kitten. Really runs out sweet. No missing at all,even compression across the board. All wiring is new. The harmonic balancer is the new design from Hot Heads Hemi that they produce specifically for this set up. Flexplate was new from Wilcap and when used the second time was balanced with the crank and checked for any cracks. I will be getting the car out of storage soon and will be checking things out for the summer runs. Like I've stated before I have put a lot of miles on this car with this problem and to date nothing has shown up that would help pinpoint where this problem is. I wish it would (be careful what you wish for) because than I could fix the situation. One far out idea that came across in a few BS sessions this winter. I am running dual exhausts with steel pack mufflers. Does anybody think that the harmonics could be from the mufflers resonating??? The vibration does change,for the better,as the engine warms up. Just a thought... I hope nobody out there thinks I'm BS'n you guys. This problem has been with this car no matter what I've done with it. One way or another I will fix this thing. Dynamite is NOT an option ......
     
  12. Andy
    Joined: Nov 17, 2002
    Posts: 4,692

    Andy
    Member

    Do you have another carb you can try?
     
  13. da dodge brother
    Joined: Apr 2, 2010
    Posts: 386

    da dodge brother
    Member
    from wisconsin

    Switched carbs twice already. Used a couple of different types ... Strombergs and Holly's
     
  14. Could it be the oil pump? I ask because you say its less when it warms up. Warm oil flows easier than cold oil.

    I dont know if a worn oil pump will cause a vibration, but since you balanced all the other rotating parts, what else is inside the engine that would be effected by warmed up oil?
     
  15. Are the mufflers or exhaust system bolded directley to the frame or body or are they hung off of rubber?I had a resonating vibration on my 36 coupe with a 440 in it and I had the exhaust mounted a little to ridged to the body.I hung it off the frame with the rubber mounts and she was all better.Another thought on my bros 33 ford coupe we got a bad converter from tci and it rattled the car pretty good.We were able disconnect the converter from the flexplate and start the car and it was smooth,so we knew the converter was the problem.Not sure if you can do that with your setup I think the converter has the starter ring gear welded on it so that probably won't work for you.
    Joe
     
  16. Just my two cents, but MOPAR liked to use flex plates that had weights vice the converter. Since the flex plate was used when when rotating assembly was balanced, I am not sure what the deal could be. The last time I experienced the same sort of issue, it was caused by a mis-matched flex plate.
     
  17. 73RR
    Joined: Jan 29, 2007
    Posts: 6,545

    73RR
    Member


    ...I'd like to see a photo of that!!

    .
     
  18. Next; Loosen the engine and trans mount through bolts, any changes?
    I have run across a few vehicles that had a strange vibration due to
    the exhaust, yes, you could get it from either internal muffler or from a
    grounded hanger or strap.
    How close are the header primary pipes to the starter or frame??
    NOTE: Just because someting is "NEW" does not mean its NOT defective!
     
  19. gonejunking
    Joined: Sep 15, 2008
    Posts: 50

    gonejunking
    Member
    from NW USA

    I would look at the back of the crank. Is it trued 90deg to the crank centerline?
    I worked at a Plymouth dealer in the early 70's, had one with just a tad off crank face.

    Just my 2c
    Jeffrey
     
  20. da dodge brother
    Joined: Apr 2, 2010
    Posts: 386

    da dodge brother
    Member
    from wisconsin

    OK. First off thank you everyone for your replies. I'm getting a few ideas. On the exhaust, we do have good clearence and the system is rubber mounted. I was wondering if the harmonics could be resonating from the mufflers up through the floorboards. And the starter gear is welded to the converter. (If I disconnect the converter think I can use a rope on the front pulley to give her a pull-- like starting a lawn mower ???)
     
  21. hemiphil
    Joined: May 6, 2010
    Posts: 25

    hemiphil
    Member
    from australia

    :) Hi from downunder, has the torque convertor got weights welded to to it? that could be source of vibration, you should balance convertor with crank, flexplate and all rotating parts.:)
     
  22. Get the torque converter spun in a lathe and check if the snout that engages the sprag isn't bent out of true. We encountered this in a race car a few years ago and believe me it vibrated the converter bolts loose also make sure your planetary shaft isn't bent. Rob.
     

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