Exhaust Manifold Studs Screwed Up

  • #1

    Exhaust Manifold Studs Screwed Up

    Hey guys,

    Just started working on my VG30ET and I pulled of the exhaust manifolds to find a pretty nasty setup. Seems that the studs holding the manifolds to the block are totally screwed up in some places--different lengths, absent in some places, etc. I attached some pictures.

    The first picture shows the driver's side manifold while attached. On one end, there isn't even a stud with nut, there's just a bolt jammed in there. You can also see one nut with like half a dozen washers below it. The second picture shows the damaged port on the block that the stud should have gone into, but instead held a bolt. A few of the other holes on the block are also screwed up.

    That bolt and damage to the block worries me, have a feeling it can't be easily fixed? The other side is pretty bad as well--one stud snapped off with all different lengths of studs in various ports.

    This is my first time rebuilding an engine, so I'm not sure if this is OK or not. Seems pretty precarious to me.
    View of the exhaust manifold (I know the valve cover is off, had to remove that to get engine out). Closer view of that messed up port on the block.
    2 Photos
    Last edited by Kihnspiracy; 02-14-2017, 04:27 PM.
  • #2
    Thread chasing:

    Remove all studs/bolts and chuck them in the garbage, Get a quality M8X1.25 thread tap, you want a "plug tap".
    Use it to clean up the threaded stud holes.
    Flush the threaded holes of debris with an air gun or lubricant and see what the threads look like with a LED light.
    Hopefully they're OK.

    The one with the stud broklen off, It looks like someone tried to drill it out and failed.
    1. Rotate the engine stand so that it is facing upward and use some PB Blaster to soak it overnight, or for a good long while. Sometimes these are actually loose in the head and only held in by some gunk in the threads, the PB blaster will help solvent that.
    2. If you have a center punch, use it to make an indentation in the top of the stud. This gives you a place for the next step and helps break loose the broken part.
    3. Use one of these or these to remove the stud. They work extremely well.
    tl;dr:

    https://www.youtube.com/watch?v=rNgpDYGcMsU


    You will want a replacement set of cast exhaust washers. They're thick to spread the clamping load and not degrade.
    I get mine from other VG30 engines at the Pick-n-pull.
    Exhaust studs can be purchased here. They are M8x1.25mm x 30mm
    Last edited by Z_Karma; 02-12-2017, 11:20 AM.


    84 AE/Shiro #683/Shiro #820/84 Turbo
  • #3
    Originally posted by Z_Karma View Post
    Thread chasing:

    Remove all studs/bolts and chuck them in the garbage, Get a quality M8X1.25 thread tap, you want a "plug tap".
    Use it to clean up the threaded stud holes.
    Flush the threaded holes of debris with an air gun or lubricant and see what the threads look like with a LED light.
    Hopefully they're OK.

    The one with the stud broklen off, It looks like someone tried to drill it out and failed.
    1. Rotate the engine stand so that it is facing upward and use some PB Blaster to soak it overnight, or for a good long while. Sometimes these are actually loose in the head and only held in by some gunk in the threads, the PB blaster will help solvent that.
    2. If you have a center punch, use it to make an indentation in the top of the stud. This gives you a place for the next step and helps break loose the broken part.
    3. Use one of these or these to remove the stud. They work extremely well.
    tl;dr:

    https://www.youtube.com/watch?v=rNgpDYGcMsU


    You will want a replacement set of cast exhaust washers. They're thick to spread the clamping load and not degrade.
    I get mine from other VG30 engines at the Pick-n-pull.
    Exhaust studs can be purchased here. They are M8x1.25mm x 30mm
    Sweet, thanks for the information!! Really appreciate it.

    What do you think I should do about the damage on the hole where the bolt went in? The second photo shows the damaged hole. There was an oversized bolt stuck in there when I pulled the manifold off, a stud will not screw back in and its too big for the proper tap.

  • #4
    You could try a Heli coil kit:

    http://www.oreillyauto.com/site/c/detail/HEL0/55468.oap



    84 AE/Shiro #683/Shiro #820/84 Turbo
  • #5
    Originally posted by Z_Karma View Post
    You could try a Heli coil kit:

    http://www.oreillyauto.com/site/c/detail/HEL0/55468.oap
    Prefect, thanks!
  • #6
    When putting back together it is highly recommended to buy a ARP exhaust stud kit for a LS1. They are the proper thread size for the VG30 heads and will not break. You must have some 12-point sockets for the ARP nuts. Use plenty of anti-sieze.

    1986 300ZX Turbo…sold
    1990 Skyline GT-R…new money pit
    2014 Juke Nismo RS 6-speed…daily
  • #7
    Every time i look a ARP pricing, my wallet lets out a whimper.

    I plan to go the budget route from McMaster-Carr on my next build.
    1 1 pack 93245A149 Nonmarring Flat Point Socket Set Screw, Alloy Steel, M8 Size, 30mm Length, 1.25mm Pitch, packs of 25 $9.41 pack 9.41
    2 1 pack 93162A320 Blue-Dyed Steel Oversized Washer for M8 Screw Size, 9 mm ID, 17 mm OD, packs of 50 10.67 pack 10.67
    3 1 pack 90716A102 High-Strength Steel Serrated Flange Locknut, Class 10, M8 x 1.25 mm Thread, packs of 50 11.23 pack 11.23
    Total: 31.31

    M8 Set screw is Rockwell C45 (206,000 psi tensile strength)
    M8 washer is Rockwell C38 (176,000 psi tensile strength)
    M8 flanged nut is grade 10

    Optionally, you could go with 316 stainless steel and sacrifice tensile strength for corrosion resistance
    1 2 packs 92605A152 Nonmarring Flat Point Set Screw, 18-8 Stainless Steel, M8 Size, 30mm Length, 1.25mm Pitch, packs of 10 $7.10 pack 14.20
    2 12 each 93849A105 18-8 Stainless Steel Oversized Washer for M8 Screw Size, 8.4 mm ID, 16 mm OD 1.17 pack 14.04
    3 2 packs 92773A102 316 Stainless Steel Serrated Flange Locknut, Super-Corrosion-Resistant, M8 x 1.25 mm Thread, packs of 10 5.41 pack 10.82
    Total 39.06

    M8 SS Set screw is Rockwell B80 (73,000 psi tensile strength)
    M8 SS washer is Rockwell B83 (78,000 psi tensile strength)
    M8 SS flanged nut is not specified


    Without doing any of the above research, i blindly used ACE hardware SS M8X1.25X25 hex head bolts, stock washers and copper anti-seize on my 84T build and have had to re-tighten them only once in 15 years.

    I've learned s bit about fasteners since then and i plan on replacing them with the higher strength McMaster option above when i service it later this summer.
    Last edited by Z_Karma; 02-16-2017, 04:18 PM.


    84 AE/Shiro #683/Shiro #820/84 Turbo