Rb25 Head Stud Thread Pitch/size

[iruvyouskyrine]

As title states, anyone know the thread pitch/size for RB25 head studs/bolts? Need to get the correct tap to clean out the holes.

[scotty nm35]

M11 standard i'm pretty sure (from ARP), no idea on the pitch though. I had to buy one for the VQ as they run the same M11 thread on the head bolts.

Make sure you get a bottoming tap.

[iruvyouskyrine]

Yeah right that's odd. Best place to get a tap scotty? Blackwoods etc or online?

[White GTS-T]

Just be aware that a tap will 'cut' a new thread, whereas a thread chaser will 'clean' the thread.

[White GTS-T]

Chase kit for reference.

[iruvyouskyrine]

Oh nice! Will make sure that's what I get, thanks mate

[GTRPSI]

To be more exact its actually M11 X 1.5 (pitch) for RB25's and RB30's.

RB26's are M12 X 1.5 pitch.

Reason i know is because im about to convert a RB30 block to RB26 head bolt sizes tomorrow for fun.

Make sure you get the bottoming out tap so yo can reach the end of the threaded hole if cleaning threads, the next one back is the plug tap and will be short 3-5 turns from the bottom, the starter tap will be 5-8 turns short.

[scotty nm35]

Do you have the length Pete? I want to compare to the VQ bolts I have here. (Not that I really want to go cutting L19's down, but I will if I have to. )

[GTRPSI]

Im waiting on 12mm CA625+ studs to arrive and a i have a set of 11mm studs but the box is sealed and i dont want to open it as im selling them.

A stock RB26 head bolt with washer fitted is 99.91mm long from under the washer head to the very end of the bolt including the threaded section that enters the block.

Remove the washer and from under the bolt head to the end of the threads its 102.72 mm.

Washer is 3.10mm thick exactly. (so im a few 0.00mm out somewhere)

Threaded section entering the block from the lengths above is around 27.5mm.

From there you will just need to add what you need to protrude out of the head to get the nut full on when working out stud lengths.

[GTRPSI]

Do you have the length Pete? I want to compare to the VQ bolts I have here. (Not that I really want to go cutting L19's down, but I will if I have to. )

I was just down at Barrys and he gave me a set of RB26 ARP2000 stud kit to measure up as im still waiting for my studs to arrive.

Complete length of the whole stud is 124.37mm end to end.

Threaded section that enters the block is 23mm

74.27mm un-threaded shaft length.

Threaded section that nuts go on is 27.1mm.

So 23mm into block, 74.27mm shaft length, 27.1mm threaded for nuts and washer=124.37mm total length.

Hope that helps you.

[scotty nm35]

The VQ bolt is 120mm from under the washer to the tip of the thread, so the length would be perfect, but it has an M11 x 1.25 pitch, so if the RB25/30 is 1.5mm pitch that won't work unfortunately.

[GTRPSI]

Are you sure its 1.25 pitch into the block? It would provide real torque when tightening down.

Whats the final torque on them? A lot less than 100ft/lb?

ARP's studs for 25's and 26's are 1.5 pitch into the block but (i think) 1.25 on the heads nut face end. (Much finer)

[scotty nm35]

Yep, I was measuring the stock VQ25det head bolts, so it's the thread into the block. I can't remember the nm figures, but 76nm stock and 96nm for the L19's is stuck in my head for some reason, unless it was actually ft/lb figures.