WTF is this noise, and why is it happening??

Discussion in 'Classic Mustang Specific Tech' started by woodsnake, Dec 17, 2011.


  1. woodsnake

    woodsnake Active Member

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  2. Noobz347

    Noobz347 Stangnet Facilities Maint Tech... Er... Janitor Admin Dude

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    Sounds like a rocker tapping the valve cover.
     
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  3. chepsk8

    chepsk8 Founding Member

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    Agreed. If the Cobra valve covers you have are the standard ones, they will not clear the roller rockers, and they'll hit the oil and pcv baffles. I had the same issue issue with my aluminum covers with the GT-40 heads, so I machined the baffle mounts higher up so there was clearance. Quick way to tell is check for the location of the noise with a stethoscope or the screwdriver trick, and/or quickly run the car with the valve covers off or raised up 1/4". No noise, bingo. Also look for impacts on the underside of the valve covers.

    Dan
     
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  4. woodsnake

    woodsnake Active Member

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  5. Noobz347

    Noobz347 Stangnet Facilities Maint Tech... Er... Janitor Admin Dude

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    You changed the heads and got this noise afterward. Got it (unless I'm not understanding correctly).

    --so--

    --and--



    It still sounds like a rocker tapping on the valve cover whether it's the result of larger roller rockers that chepsk8 mentions above or a fulcrum bolt loose, or stud that's either broke or stretched, or not screwed down all the way or whatever. Pull the valve covers and check.
     
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  6. woodsnake

    woodsnake Active Member

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    I will pull the valve covers and confirm, but in person the noise is coming out of the rear carburetor.
     
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  7. Noobz347

    Noobz347 Stangnet Facilities Maint Tech... Er... Janitor Admin Dude

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    Could very well be but we don't get the directional sense from the video that you get being in front of it. Can only tell you what it sounds like. I do hope though, that the problem is as simple as rocker tap.
     
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  8. chepsk8

    chepsk8 Founding Member

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    If not, a bent valve or something equally ugly...
     
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  9. dennis112

    dennis112 Active Member

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    Did you consider that the head swap might require a different length pushrod?
     
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  10. Noobz347

    Noobz347 Stangnet Facilities Maint Tech... Er... Janitor Admin Dude

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    I thought about that too. The sound clip sounds like a single tap though vs. multiple. :shrug: Who knows though... might be a possibility.
     
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  11. jcode68

    jcode68 Active Member

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    Sounds familiar! Definately rocker. On mine, the rocker lock nut had backed all the way off and the rocker was flopping around. Sounds like a couple of marbles under the valve cover. Don't run the engine anymore until you pop the cover and have a look. Need to make sure the lock nuts are torqued properly so they don't back off.
     
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  12. 68dustin

    68dustin Member

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    not to sound like u dont know what ur doin, but were all tools accounted for?? didnt leave anything under the intake in the valley?? ive seen it happen before, so just a thought?
     
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  13. woodsnake

    woodsnake Active Member

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    No tools left over, we did check. I bought the heads several years ago, and just got around to installing them a few weeks ago. I took them to the machine shop, and ordered/installed the right springs for the cam that I already had in the motor. I don't know what happened between the 2nd video I posted, VS the first one. The engine is fresh, it only has about two and a half thousand miles on it. It is the Performer RPM cam, .496/.520 for lift specs. The Edelbrock dual quad package, on a .030 over 289 block. I had to learn the hard way about push rod length, springs, installed height, etc...I drove the car to my buddy's house with a garage, and we took the iron heads off. I had the machine shop verify that the springs I had that came with the heads were either good, or not. They said no, so I had them install springs that met the installed height/rate requirement. The overall height was maintained, so no PR change was in order. I re-verified the valve stem tip before we buttoned up the motor, and put it back together. In person, it sounds like it is backfiring up through the carb, there is only slight roller rocker noise coming from under the valve covers.
     
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  14. 68dustin

    68dustin Member

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    did u check the piston to valave clearance?
     
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  15. woodsnake

    woodsnake Active Member

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    Yes, I did. The Edelbrock heads have bigger valves, so we verified clearance.
     
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  16. palerider94

    palerider94 Member

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    my money is on rocker hitting valve cover as already mentioned.
     
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  17. woodsnake

    woodsnake Active Member

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    Wouldn't that make a more consistent noise?
     
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  18. bikefreak600

    bikefreak600 Member

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    if the rocker is loose and bouncing around it could randomly hit. my brother unknowingly dropped a washer down his intake one and started the motor, it made it into a cylinder and bounced around. sounded like the whole motor fell apart lol
     
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  19. pabear89

    pabear89 Active Member

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  20. azduffee

    azduffee New Member

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    It's possible you have a valve hanging/sticking in the guide. The valve guide clearances on new Edelbrock heads are always a bit tight and I hone them to size. Just another idea. The FIRST thing I would do is remove the valve cover and inspect things like many have suggested.
     
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