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3/8 Off-set Dowel Pins

Discussion in 'Early CJ5 and CJ6 Tech' started by tripilio, Feb 27, 2020.

  1. Feb 27, 2020
    tripilio

    tripilio Proud American!

    Miami
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    Where can I get a set of 3/8 off-set dowel pins? My bellhousing is off by 20 thousands TIR. That is after installing the dowel bolts and torquing the bellhousing to the block. Do the bolts have an orientation when installing them? Thanks!
     
    Last edited: Feb 27, 2020
  2. Feb 27, 2020
    tripilio

    tripilio Proud American!

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    BTW, I'm mating aT90 to an F134.
     
  3. Feb 27, 2020
    Tom_Hartz

    Tom_Hartz Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Summit racing maybe?
     
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  4. Feb 27, 2020
    tripilio

    tripilio Proud American!

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    I guess I could call them. The do not list anything 3/8 on their page, at least that I could find.
     
  5. Feb 28, 2020
    tripilio

    tripilio Proud American!

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  6. Feb 28, 2020
    Rich M.

    Rich M. Shoe salesman 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    20thou is a crap ton. I'd mark the housing up and take it to a shop with the bearing retainer. A T90 could probably deal with 10 but that's on the upper end. You may want to try a different bellhousing too. F bellhousings are not scarce at all.
     
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  7. Feb 28, 2020
    MikeON

    MikeON New Member

    Lucinda PA
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    This is what I did. Two and a half years later it is still running well. Smooth, quiet, and stays in gear.
     
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  8. Feb 28, 2020
    tripilio

    tripilio Proud American!

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    I know! That is a great idea. Do you remember the actual measurement of the bolts? If you reamed at 7/16 you must have made the bolts undersized to have a slip fit, right?
     
  9. Feb 28, 2020
    duffer

    duffer Rodent Power

    Bozeman, MT
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    Are the pins actually 0.375"? Chevy uses .316 dowels for their gen I small block heads and Moroso has offset versions in .015 and .030.

    https://www.summitracing.com/search/product-line/moroso-offset-cylinder-head-dowels/part-type/cylinder-head-dowel-pins/make/chevrolet/engine-size/5-7l-350/engine-family/chevy-small-block-gen-i?autoview=SKU&keyword=offset dowel pins&sortby=BestKeywordMatch&sortorder=Ascending
    ARP has tight fitting bolts that may not need any machine work. But like others stated, I would just use another bellhousing. The closest thing Summit has is their offset sbc head dowels but those are just 0.316" IIRC.
     
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  10. Feb 29, 2020
    MikeON

    MikeON New Member

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    I turned a little at a time off the bolts and tried them in the reamed holes until they were a very light tap fit. Turned between centers so they could be removed from lathe and put back in with perfect alignment. I made them a little long, then cut some off the threaded end, which is why no center holes showing on that end in the picture. I think they ended up right on 7/16" (.4375). Then threaded with standard 7/16" fine thread. I chose this route over offset dowels because the dowels provide no clamping force between the engine and bell housing.
     
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  11. Feb 29, 2020
    CHUGALUG

    CHUGALUG Member

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    The two bottom bolts on a 2A or 3A or newer bell housing have to be exactly .375" D that is why these bolts are originally a special shouldered bolt. This is where the alignment comes from. The shorter bolts used with the 2A bellhousing (starter bushing in bell housing) are available the long ones (used with a 3A bellhousing enclosed nose starter) can only be found used and are super hard to find. A replacement can be made using .375" O1 Drill rod (you can buy 12" off ebay) cut the rod and thread both ends it will be a tap fit (small hammer) it has to be this tight to work properly.

    If you have .020" off set something is junk.
     
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  12. Mar 2, 2020
    duffer

    duffer Rodent Power

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    Those ARP bolts I mentioned above do have a 0.375" diameter grip length for their 3/8". I have become a real believer in ARP's collection. IMO, the best fasteners you can purchase off-the-shelf.
     
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  13. Mar 5, 2020
    tripilio

    tripilio Proud American!

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    Finally, I decided to make my own off-set dowel pins. I will try them soon to see if they work. I could not find anything on any supplier on 3/8 so I decided to fabricate them myself. After several (bad) ideas and tries, I came up with this. I turned them below .375, so it will give me a loose slip fit and will slide and rotate freely. Since my TIR is about 0.020 I made the off-set about 10. I don't know if this is going to be too much. If anything I can always modify them to a different off-set number. Let's see...
    20200305_135605(0)_copy_774x1032[1].jpg
     
  14. Mar 5, 2020
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    That's very clever. I realize the whole assembly slides into a 3/8" hole, but I must admit it reminded me of this classic:

    [​IMG]
     
  15. Mar 5, 2020
    tripilio

    tripilio Proud American!

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  16. Mar 6, 2020
    tripilio

    tripilio Proud American!

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    Update: I had to modify the off-set bolts since they had no way to be installed. Fireball, you were right, it was like the first bolt from your list!

    20200306_160914_copy_774x1032.jpg
     
  17. Mar 6, 2020
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Hah! Nice work on these though. It looks like your offset is 0.100 and not 0.010? Seems big.
     
  18. Mar 6, 2020
    tripilio

    tripilio Proud American!

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    :confused: I'll double check. I had to re-set them a few times to achieve parallelism and maybe I missed a zero or two. Looking at them again it does seem like a lot. As I'm getting older I realize I cannot carry two jobs and two sets of measures in my head at the same time anymore . I did those at work while working on something else. Oh, well!:crazy:
     
  19. Mar 6, 2020
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    In the last couple of months, I can't tell you how many times I've measured for a piece of trim, walked 20ft to the room where the chop saw is and completely blanked on the measurement.

    Working full time, having 2 puppies and trying to remodel a house all that the same time.....
     
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  20. Mar 10, 2020
    tripilio

    tripilio Proud American!

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    You, sr were absolutely wrong! Of course it was not 0.100... it was 0.120!:rofl:
    I will work on it to make it 0.010. Would that be enough to correct a 20 thousands TIR?
     
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