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Bellhousing Bolts


webdawg1

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Anyone know right off the top of their head what the correct OEM bolt strength was/is for the bellhousing mounting bolts. (75 280Z , 4 speed manual) Got a couple on the bottom that look kind of rough so I thought I'd look around for suitable replacements. I know what size and thread pitch they are, (10mm x 1.5 x 60mm) just need the strength rating...

webdawg1

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Are you sure they are 1.5 pitch? I only ask because nearly all the 10mm bolts that I have encountered on the car are 1.25 pitch, same for the 12mm bolts.

These bolts will be exposed to the elements, so they either need to be stainless steel or plated/coated, eitherwise they will rust right up. Might as well buy Grade 8 bolts as well (which is the typical grade for automotive fasteners on our Zs).

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Yeah, I'm sure.... Believe it or not, I carry both SAE/Metric thread gages on my key chain and my trusty 4-way Sears pocket screwdriver. LOL When I'm at the house and working out in the garage I also use a bolt size gage I got from www.fastenal.com as well as the metric thread gage to verify the thread pitch and bolt/screw size.

webdawg1

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I concur. They are 10 mm x 1.5 x 60 mm in length. 65 mm long will also work if that's your closest choice. The most commonly found generic bolts are either 50 mm long (too short) or 75 mm which is too long and will bottom out before they get tight.

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Anyone have a good tech article on the OEM head bolt markings that were used when these cars were first put together? Or is there such an animal??? On one of the Bellhousing Bolts the head marking looks like 1 9. Or it could be 6 1 if you rotate it 180 degrees, but then the 1 does not look right...if you know what I mean....

webdawg1

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I just went out and checked, it looks like I re-used the factory bolts. If I remember I couldn't find bolts the right length.

Just a guess, but the "1 .9" marking could easily be a slightly worn "10.9", which is a metric strength class. (Equal to ANSI grade 8)

If I was going with after-market bolts I would use that grade. But is there a clearance problem with the head... I just don't remember.

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That would be kind of interesting to find out.... I've seen various markings on the bolts...mostly 4, 7 , and 9 1. And then some of them have no markings at all...From what I've found so far it appears to be standards related (JIS) Kind of like our SAE...but nothing about the bolt head markings...

webdawg1

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There is a chart on page 158 of Wick Humbles book, How to restore your Datsun Z-car, that lists the torque specs for the various size and grades of bolts used on the car. He states that the ISO grade is embossed on the bolt head.

FWIW

Todd

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