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Thread: 3.0 Tapping Noise

  1. #21
    Senior Member
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    So...found the source of the noise.

    12E6ACA8-11DF-47AD-8B33-F881992C55D8.jpg
    7822EFC4-F7AD-4188-B201-6D1CF9C61BA2.jpg

    Crappy Fel Pro exhaust gasket didn't work too well. #4 was the worst and it makes sense as most noise was from that area.

    New DMCH gaskets coming Wednesday. Bought from them as I needed a new bowden cable and a pretty DMC sticker to go on 3.0 cover.

    Maybe Josh Bengston could answer this? Should I add more manifold studs, or is it fine with the 2 for each cylinder?
    Early 81 5spd conversion- DMCH Ground Effects, Double Din, Custom Instrument Cluster, QA1 Suspension, 3.0 PRV with MS3

  2. #22
    DMC Timeless's Avatar
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    Good news it's not a more significant issue. For over 10 years I never had issues with FelPro gaskets at my shop although, they could be made with subpar quality now. (i.e. China)
    ~LXA~
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  3. #23
    President, DeLorean Industries
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    We recommend four to a cylinder. Glad you found the issue!
    www.deloreanindustries.com Every Detail Matters

  4. #24
    LS Swapper Josh's Avatar
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    if your flanges are flat, there is no reason to have more than two studs per cylinder. You can install more studs to try and flatten out a warped flange, but it really should be milled down which can be done by most machine shops. I would check it with a straight edge before you throw on new gaskets.

    Having four studs a cylinder is not common practice with other engines, it gives more failure points (rusted/snapped studs) and makes it more difficult to install the headers.

    Supercharged 5.3L LS4 + Porsche 6spd
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  5. #25
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    Aaaaand spoke too soon. Put new gaskets and noise is still there.


    Maybe it's oil coming past rings making that noise? Or just valve train?

    I'm about to to give up, put some serious miles and see if it blows or eats a cam.
    Early 81 5spd conversion- DMCH Ground Effects, Double Din, Custom Instrument Cluster, QA1 Suspension, 3.0 PRV with MS3

  6. #26
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    Also, for Josh B.

    I started it without cats connected and no vibrations at all. Very smooth. Hook cats and tighten band clamps and vibration returns.
    Early 81 5spd conversion- DMCH Ground Effects, Double Din, Custom Instrument Cluster, QA1 Suspension, 3.0 PRV with MS3

  7. #27
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    I?m hearing most of the noise where all the tubes meet at collector. Going to check with vacuum cleaner and soapy water when it cools down.
    Early 81 5spd conversion- DMCH Ground Effects, Double Din, Custom Instrument Cluster, QA1 Suspension, 3.0 PRV with MS3

  8. #28
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    Unhappy

    So even with brand new gaskets, it still leaks! Anybody have an idea how this can be fixed?
    Early 81 5spd conversion- DMCH Ground Effects, Double Din, Custom Instrument Cluster, QA1 Suspension, 3.0 PRV with MS3

  9. #29
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    Header is warped about .018 of an inch

    Going to call DPI tomorrow to see best course of action.
    Early 81 5spd conversion- DMCH Ground Effects, Double Din, Custom Instrument Cluster, QA1 Suspension, 3.0 PRV with MS3

  10. #30
    President, DeLorean Industries
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    We would run the flange across our surface grinder, fuse dress the ports and pressure test on our platen fixture. These are the final steps of making a header in-house. The warpage of .018 on a flange would be considered nominal. It is not much and would draw closed against a quality gasket and two prepped surfaces. Is there is any pitting on the cylinder head port sealing areas? Four bolt flanges are the aftermarket header manufacturer’s ideal situation. The idea of being able to secure a port in such a fashion gives unbelievable levels of excitement in the aftermarket industry. While an OEM manifold may work fine with two points, the thermal expansion characteristics of a flange with .065 wall tubing moving under heat loads are very different by contrast. Headers bolted opposite each other exhibit a pringle event during various engine loads. This can be visualized by setting a pringle chip on a flat surface. Regardless of how the chip faces, the two edges contacting the surface represent the flange bolted point. The two perpendicular edges not contacting represent the section of the flange not held around the port. This is a solid visual representation of how the joints function under various heat loads over cycled application use. Not having clamping force evenly spread around the sealing joint is an issue.

    Edit:
    Also, just saw the above video after logging in. That is a very low-quality single-layer exhaust gasket. Would recommend using a better gasket. Where is that from?
    Last edited by Delorean Industries; 01-26-2023 at 07:44 AM.
    www.deloreanindustries.com Every Detail Matters

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