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Thread: 4BD1/T Head bolt quantity, source, PNs etc ??

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    rijidij's Avatar
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    4BD1/T Head bolt quantity, source, PNs etc ??

    I've been trying to source a set of head bolts for my 4BD1T so I can replace the head gasket, but it's proving a little difficult.
    My local (Non dealer) truck parts suppliers don't have them.
    My local Isuzu dealer can get them, but there's some confusion over the quantity. He says I need 12 x 115mm bolts PN 8943674380 (Superseded by PN 1090701011)
    But reading on AULRO it sounds like I might need 14 bolts of one length, and 4 bolts of another length. The dealer did have a separate PN for 4 x 102mm bolts PN 10900701001 (ex Japan).
    For such a common truck engine (even though they're getting on a bit) you'd think it would be pretty simple.
    From what I've read it seems the head bolts are the same for N/A or Turbo variants.
    So, I'm looking for some clarification as to what bolts I need because even the Isuzu dealer didn't know for sure.
    Has anyone sourced good quality head bolts in Australia recently, if so, where ?
    It would be great if someone has them in stock.

    Also, even though I'd prefer to get new bolts, is it ok to re-use the existing bolts ? I'm not sure if they're torque to yield, but the last step of the tightening process is a degree rather than a torque value, which makes me feel they shouldn't be re-used.

    Thanks for any help.

    Cheers, Murray
    '88 County Isuzu 4Bd1 Turbo Intercooled, '96 Defender 130 CC VNT
    '85 Isuzu 120 Trayback, '72 SIIA SWB Diesel Soft Top
    '56 SI Ute Cab


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    I had this conversation with KLR and for all applications they inspect and re-use.

    I saw your FB post and commented on the fact the manual only supplies 'new vs reused' torque values (2 step) for the NA ....and only one tightening sequence (2 step torque+ angle) for the turbo.

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    My Isuzu factory workshop manual for the NA 4BD1 shows 18 head bolts tightened in the usual spiral pattern. The bolts are to be tightened in three steps and the book expresses the torque values in kg-m. First step 6.0, second step 9.5, third step 11.5. Oiled threads. no mention of tightening by degrees or one use bolts.
    URSUSMAJOR

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    Quote Originally Posted by Bigbjorn View Post
    My Isuzu factory workshop manual for the NA 4BD1 shows 18 head bolts tightened in the usual spiral pattern. The bolts are to be tightened in three steps and the book expresses the torque values in kg-m. First step 6.0, second step 9.5, third step 11.5. Oiled threads. no mention of tightening by degrees or one use bolts.
    That is contrary to my manual that came on the 4bd1 disc in the shop.

    What year is your manual? Mine is 1986 onwards and IDE2140

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    Quote Originally Posted by BadCo. View Post
    That is contrary to my manual that came on the 4bd1 disc in the shop.

    What year is your manual? Mine is 1986 onwards and IDE2140
    Mine is IDE2050.

    I also have an industrial engine manual without a part no. It mentions tightening procedure for both laminated steel gasket, first step 7.0, second 9.0 +/- 0.5, third 90 degrees + 30 degrees. Steel asbestos sandwich gasket, first step 7.0, second (new bolt) 9.5 =/- 0.5, Reused bolt 11.5 +/- 0.5.

    IDE2050 was purchased from Brisbane Isuzu, the truck dealers, and the industrial one from Zenith Engineering, the industrial engine distributor.
    URSUSMAJOR

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    Quote Originally Posted by Bigbjorn View Post
    Mine is IDE2050.

    I also have an industrial engine manual without a part no. It mentions tightening procedure for both laminated steel gasket, first step 7.0, second 9.0 +/- 0.5, third 90 degrees + 30 degrees. Steel asbestos sandwich gasket, first step 7.0, second (new bolt) 9.5 =/- 0.5, Reused bolt 11.5 +/- 0.5.

    IDE2050 was purchased from Brisbane Isuzu, the truck dealers, and the industrial one from Zenith Engineering, the industrial engine distributor.
    Interesting! So who do we believe then? Maybe the IDE2050 is pre 86 motors...

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    It seems there have been a few different versions of manuals over the years,

    This is from one I downloaded.........

    Head-Bolt-Torque-1.jpg

    These are some others posted on Facebook discussions.............

    Head-Bolt-Torque-2.jpg

    Head-Bolt-Torque-5.jpg

    Head-Bolt-Torque-4.jpg

    This one is referring to 'Retensioning', so probably not relevant to this discussion

    Head-Bolt-Torque-3.jpg
    '88 County Isuzu 4Bd1 Turbo Intercooled, '96 Defender 130 CC VNT
    '85 Isuzu 120 Trayback, '72 SIIA SWB Diesel Soft Top
    '56 SI Ute Cab


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    Quote Originally Posted by 87County View Post
    Well, that's a different one again, only 30 degrees for the final step.
    '88 County Isuzu 4Bd1 Turbo Intercooled, '96 Defender 130 CC VNT
    '85 Isuzu 120 Trayback, '72 SIIA SWB Diesel Soft Top
    '56 SI Ute Cab


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    rijidij's Avatar
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    As suggested on another forum, this torque sequence, with new bolts (if I can get someone to supply the damn things) makes the most sense to me as I have a factory turbo engine running more than standard boost, nothing extreme, approximately 16-18psi Max (Factory is 13psi)
    And, by the way, the gasket I've ordered is a multi layered steel type.

    Head-Bolt-Torque-6.jpg
    '88 County Isuzu 4Bd1 Turbo Intercooled, '96 Defender 130 CC VNT
    '85 Isuzu 120 Trayback, '72 SIIA SWB Diesel Soft Top
    '56 SI Ute Cab


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