Bolts specifications

[falcon_ca]

Because I dont want to remove engine and tranny to pick-up samples and I need those bolts for my 4.9 project, I am looking for the specs (dimension grade etc...) for the Flywhell bolts (to the crank) and the pressure plate bolts (to the Flywheel).

Anybody have that ?

[aaron88]

My northstar flexplate bolts were 9.8 but what you use depends entirely on what tourquing procedure you are planning on using.  I would recommend using whatever bolt hardness your 4.9 flexplate came with and tourqu as per your 4.9 spec.  When in doubt have a look at another 4.9.
For the length, you have to take out the 4.9 flexplate bolts, measure the length, add the thickness of your flywheel mounting surface, then you’ll have your number.  Never trust someone else to give you the information that might save your life.  That thing is spinning right behind your back.

Aaron

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[falcon_ca]

Thanks Aaaron,

4.9 owners told me to go with V6 bolts for both, flywheel and pressure plate.

Most of the guys goes with their old bolts, and, as you mention, I dont want to havr something used spinning at 4000 Rpm so close to my back.

That is why I am looking for those specs.

I already found that Flywheels are M10x1x23 10.9 PC (GM 478576) and Pressure plate are M8x1.25x20 10.9 PZOR (GM 11508687) and the lock washer dimensions.

For my understanding, is there somebody who can translate those numbers and codes in size, leanght strenght ?

[dguy]

I already found that Flywheels are M10x1x23 10.9 PC (GM 478576) and Pressure plate are M8x1.25x20 10.9 PZOR (GM 11508687) and the lock washer dimensions.

For my understanding, is there somebody who can translate those numbers and codes in size, leanght strenght ?

M8 = 8mm diameter (the threaded area, not the bolt head!)
1.25 = thread pitch.
20 = 20mm thread length (not including the head)

Similarly, the M10x1x23 is 10mm diameter, 1.0 pitch, 23mm long.

[falcon_ca]

 

I beleive the 10.9 is the grade, but what are the "PC" and "PZOR" ?

[aaron88]

10.9 is a metric designation for the hardness of the bolt.  The higher the number the harder the steel in the bolt.  Hardness correlates directly and linearly with the strength of the bolt.  In this case 10.9 is common among very strong but still ductile bolts.

The M means metric, the number following is the nominal outside diameter of the thread.  The number following is the distance in millimeters between threads.  In this case one bolt has an extra fine (and rare thread) and the other has a standard course thread.  The last number is the length in millimeters.  The 10.9 is the hardness but doesn’t always follow the size, it may precede it.  Your other letters are specific to the manufactures and indicates the shape of the head.  I’m not sure exactly what these letters represent but your bolt heads will have a flange on them so that the contact surface with the face of the flywheel will be round.

Do not use washers or lockwashers.  Use a flanged bolt and thread locker.

Generally if your torquing procedure does not torque to yield (torque pass the plastic deformation of the bolt) then you may re-use your bolts (not in this case though because your existing bolts will be the wrong length).

I hope some of this helps.

Cheers,

Aaron

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[falcon_ca]

Thanks Aaron,

Very clear description.

About the lock washers, they are for the pressure plate to flywheel installation.

The flywheel to crank bolts, on th 4.9, are for a flexplate and, of course,  to short for a Flywheel.

I also plan to use "lock-tite" on every bolt.