Knock/rattle at lowish rpm. 455

Discussion in 'Street/strip 400/430/455' started by hunter7389, Jul 16, 2017.

  1. hunter7389

    hunter7389 Well-Known Member

    Hi folks, have a recently rebuilt 455 in a 69 skylark. Stockish compression and heads from what I know. Stock manifolds, a TA-212 can, and power timed points style dist with pertronix and coil. Last week I installed a complete Holley Sniper EFI, with the tanks inc tank, walbro in tank pump, and associated lines and filters. It's been running incredibly well, but it's not a race car. It's my daily driver. It's mostly been part throttle with an occasional trip up to 4krpm, just letting the efi learn.

    A couple days ago, it started making a rattle around 1500 rpm with light throttle in gear, I backed off right away. In park, it revs cleanly and quietly. There is 1/2 tank of Chevron 92 octane in the tank.

    While poking around, I found a Burbley noise, the mechanical fuel pump with no lines is doing that, just pushing air. Block off plate on the way. The valvetrain appears solid, no bent pushrods or loose springs, etc.

    Any ideas? Sorry for the long rambling post, I tried to get as much info as possible. Could the mechanical fuel pump arm be bouncing off the cam, now that there is no load (fuel) to be pushed?
     
  2. Mark Demko

    Mark Demko Well-Known Member

    Can you post a video?
     
  3. Stevem

    Stevem Well-Known Member

    So it sounds like this is a rebuild that was not done by you?
    If the only thing that changed was going from a Carb set up with no engine noise , to EFI and noise then I think you have your answer, it's part throttle lean, or your timing has changed.
     
  4. hunter7389

    hunter7389 Well-Known Member

    Right, it's was done, changed hands once more before I bought it. All appearances show it to be pretty stock. The car ran perfect through the first week of the efi, AFR remains on target, but ill recheck the timing to make sure it has not moved.
     
  5. hunter7389

    hunter7389 Well-Known Member

    Dialed the timing back a bit from 12/38, where it was running great, to 8/34, no change. I removed the fuel pump, which got rid of the burble, but the knock/rattle is still there, right around 1700rpm with any more than gentle throttle. The AFR is spot on with the sniper handheld monitor. Grr... Torque converter bolts are tight, flexplate is not cracked.
     
  6. hunter7389

    hunter7389 Well-Known Member

    Oil pressure remains the same, 15ish at idle hot, 25 just off idle
     
  7. hunter7389

    hunter7389 Well-Known Member

    Does it right at 1700rpm regardless of throttle position
     
  8. hunter7389

    hunter7389 Well-Known Member

    Just pulled the rocker shafts and pushrods (cam/pushrods/lifters all from TA PERF less than 100 miles ago). Everything looks great, no funny wear marks, bends or anything. Valve springs and retainers are all in good shape too. Started the engine with the valve covers off, all rockers are moving the way they should, and oil is flowing out of the pushrods like it should. Motor mounts are tight, and all accessories are securely mounted.

    Starting to not like the sounds of this...
     
  9. 8ad-f85

    8ad-f85 Well-Known Member

    How much vacuum advance?
    Is distributor beginning to stick or return slowly?
    The grease can dry out in the shaft
     
  10. Mark Demko

    Mark Demko Well-Known Member

    Rod bearing, or bearings.
     
  11. Stevem

    Stevem Well-Known Member

    Well I guess it time to pull the plug wires one by one to see if the noise goes away, if so I foresee some level of a rebuild in your near future!
    One quick check would be to see if your heat riser flap in your Exh Manifold is just flapping in the breeze due to its load spring missing in action.
     
  12. JoeBlog

    JoeBlog Platinum Level Contributor

    I had a friend who had his engine balanced and blueprinted. He assembled the engine in his garage after the machine shop got done with everything. After running the engine over the course of a few months - and it was a good running engine - the engine developed a light rattle like you're describing. One day, I helped him disconnect everything from the front of the engine and start it. The noise persisted. About a month later I ran into him again and asked about his engine noise. It turned out he'd installed the pistons in the wrong holes (not sure in what way) and the wrist pins were the culprit. You can figure out the fix from here...
     
  13. Ziggy

    Ziggy Well-Known Member

    Many years ago,I was a Buick dealer mechanic. I had a case with a V6 engine that had a very noticeable knock above idle. After fooling around for some time, we discovered that the cam was slapping back and forth against the face of the block. The fix was a thrust spring and bearing that pushed against the inside of the timing cover and held the cam against the block face. Buick made a running change in production to include the spring in later engines. Maybe this experience will be of some help in chasing your noise.
     
  14. 8ad-f85

    8ad-f85 Well-Known Member

    Time to use some sort of stethescope or dowel.
    Not that you would expect this but they are sensitive enough to discern piston skirt and ring land problems, bearings before they fully turn.
    Cut the oil filter.
    These noises are always concerning, best of luck.
     
  15. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Does it sound like ping? Just wondering whether it is tip in ping, like the FI isn't reacting fast enough and it is lean off idle.
     
    8ad-f85 likes this.
  16. hunter7389

    hunter7389 Well-Known Member

    Cut apart the oil filter...

    [​IMG]
     
  17. hunter7389

    hunter7389 Well-Known Member

    There is no exhaust flapper, TA downpipes from the mainfolds. Also the noise is regardless of throttle position, trying to creep up on 1700rpm nice and easy or fast. About to drain the oil through some cheesecloth
     
  18. hunter7389

    hunter7389 Well-Known Member

    Oil is relatively clean
     
  19. 69GS400s

    69GS400s ...my own amusement ride!

    stick a magnet on your oil filter jewelry
     
    8ad-f85 likes this.
  20. Stevem

    Stevem Well-Known Member

    Looks like parts from a lifter including some of the plunger round wire snap ring.
     

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