75 Regal 350/4 with rattling rockers

Discussion in 'Small Block Tech' started by cheese chisel, Aug 29, 2017.

  1. Mark Demko

    Mark Demko Well-Known Member

    The rocker shaft bolts... DO NOT tighten one and move to the next, tighten each one a bit at a time, "walk" the shaft down.
     
    MrSony likes this.
  2. MrSony

    MrSony Well-Known Member

    Make sure the pushrods are actually seated properly in the little cups on the rockers. It gave me quite a start when i heard a few loud pops when the pushrods popped into place. The rocker shaft had to be tightened again. Should be able to spin the pushrods with your fingers on a bled down engine, which yours should be since I assume it hasn't been started.
     
  3. cheese chisel

    cheese chisel Member

    thanks, I put them back in with a little lithium grease and walked the rocker arms down snug - I've looked in the 1975 factory chassis service manual but I can't find the torque specs for the rocker arm bolts - this seems important
     
  4. MrSony

    MrSony Well-Known Member

    Haynes manual says 30ftlbs. But I'd say just tighten evenly with a 1/4 inch ratchet until snug. Maybe a drop of blue thread locker. Maybe.
     
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    [JP] likes this.
  6. Stevem

    Stevem Well-Known Member

    Just first make sure all the shaft hold down bolts thread into there hole nice and easy by hand with no oil on them then lube them up a bit with motor oil , then use the factory Torque spec to land them.
     
  7. MrSony

    MrSony Well-Known Member

    If you use cork vc gaskets (should get new gaskets), you can see when it starts to "squish". But just over hand tight with a nut driver would be fine enough. Criss-cross pattern.
     
  8. cheese chisel

    cheese chisel Member

    it went very well - everything's back together but it was too late in this neighborhood to start it tonight - I'll post results tomorrow :)
     
  9. cheese chisel

    cheese chisel Member

    okay it sounds better but the rattling is still there - at light throttle just before it upshifts I can still hear the pushrods and rockers rattling a little like a super-fast spray paint can being shaken - starting to sound like a worn cam maybe? - still runs smooth and strong
     
  10. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    Gently snug the valve cover bolts...those will shear off with little effort, especially for us muscle guys. I have to use 2 fingers to tighten them. haha
     
  11. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    Are you certain this isn't detonation/spark knock?

    It shouldn't be making that sound.

    As a side note, those later Buick 350's list the smaller Melling cam as the replacement for '75+, which have a super early IVC. Simply put, even with a static compression ratio as low as 7.5:1, those engines have a DCR which puts them well into 'plus' octane zone.

    Which type of fuel do you burn?

    Other than this, you should be checking out why your rockers were so loose, as others have suggested earlier that there may be come camshaft lobe issues.

    Even stock cams will wear out, especially original ones that didn't use the more modern hardening technology we have today, and with modern oils and/or too much time spent in-between oil changes, among other issues that may have caused it.
     
    Last edited: Sep 10, 2017
  12. cheese chisel

    cheese chisel Member

    I'm not sure about the spark knock, I guess it could be - I've been using 87 octane in it, I can try a tank of 91 next time but I filled up today so it will be a while

    does spark knock sound like a quiet, ultra-fast spray paint can? ... at what engine condition would I notice spark knock

    what's IVC and DCR?

    thanks
     
  13. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    Apologies for the jargon. IVC=intake valve closing. It's camshaft stuff. DCR=dynamic compression ratio, and regards camshaft relationship with piston location.

    Both IVC and DCR are related, and can affect the octane requirement of your engine, among other things.

    How long have you had the car? Has it done this the whole time or is it more recent?

    The more information you can provide, the better your questions can be addressed.

    Really bad spark knock can sound like that, yes.

    It can also be related to your ignition and timing.

    Can you post a video with good sound so that we may hear it when it happens?
     
  14. cheese chisel

    cheese chisel Member

    I've had it for about 5000 miles - it's gotten worse recently - it's always had low-mileage oil changes but they've always been longer than 3 months - it gets Castrol 20w50 with Lucas oil and occasionally Engine Restore, it seems to love both of them

    good idea about the video, I'll try to rig something up

    I tried checking the timing today before I restarted it and the timing marks are really hard to see - looks like the previous owner put a white paint park on the harmonic balancer and the timing cover and as far as that being accurate the timing is right on so I didn't mess with it yet

    both the coil and the ignition module look original 1975, I just replaced the plugs, wires, cap and rotor with the rocker arm stuff ... could something in the distributor like worn springs or the module or coil cause the type of ignition problem that would cause a noise like this but still have the engine make plenty of power and run smooth?

    it's 100% drivable as it is, I took it 100 miles to a old car roll in tonight and all I saw was smiles from old people ... it just sounds bad during certain throttle conditions
     
  15. sean Buick 76

    sean Buick 76 Buick Nut

    Sounds like either pre ignition or detonation.
     
  16. Stevem

    Stevem Well-Known Member

    X3 with the Ping and or detonation issue as this is not a rocker issue any more!
     
  17. alec296

    alec296 i need another buick

    Why are you running such thick oil? Unless your in the desert that's too thick, It will hide bearing problems until it's too late. Put a gauge on it and check the oil pressure hot.
    You could have a flexplate crack or torque converter going out. The noise happens as load come off for shift. Detontation would be more often after shift with less rpm and more load.
    If flexplate or converter is not problem, I would look at rod bearing wear with that heavy oil. Switch to 10w30 and see if noise gets worse
     
  18. cheese chisel

    cheese chisel Member

    WAIT autocorrect typo about the oil - I've always used Castrol GTX 10w30 in it - sorry about that, wouldn't use 20w50 in anything that I own

    this noise is harder to describe than I though it would be - if I rev it in the driveway I can hear the noise after the peak RPM just as it's coming down off of load - it's easier to hear when driving ... under load, the engine is smooth and the noise isn't there

    I've heard pinging a few times in my life and this doesn't really sound the same to me - not ruling it out at all though

    pinging to me sounds like the ball part in a shaken spray paint can - this rattling sounds more like the can part of shaking a spray paint can ... it also sounds eerily like what the pushrods/rockers sound like when the rocker arm bolts are loose and I wiggle them around - also, it feels like it's at the wrong load condition to be pinging - doesn't a ping happen under load?

    my feeling is maybe one or more cam lobes is worn and at certain load conditions the pushrods and rockers get floppy

    surprised about the flexplate or torque converter suggestion, that's interesting - can't say that that one makes sense to me with this noise, it definitely sounds like it's coming from the heads ... any description of what the flexplate/converter noise would sound like?

    I'm working on a way to record this while I'm driving
     
  19. alec296

    alec296 i need another buick

    If you have the flexplate with triangle shape holes it cracks commonly. Sometimes you have a slight noise just above idle on slight acceleration not in gear.And your describing a rattle just before a load change or just before the rpm drops. . Would not hurt to check the bolts for convertor and inspect flexplate.
     
  20. cheese chisel

    cheese chisel Member

    it seems like it's just after load change - and only from load to less-load
    partial-to-light load is where I notice it
     

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