240_to_miata

iTrader: (2)

Are the ARP rod bolts on the M-tuned rods torque to yield? If so can they still be reused? Is there a bolt elongation spec?

Thanks

g_reichow

iTrader: (2)

ARP's website mentions that their bolts are reusable but should be replaced when they have permanently stretched.

To quote ARP's page at : ARP-bolts.com | ARP - World-leading Fastener Technology

" As a rule of thumb, if you measure a fastener and it is .0005˝ (or more) longer than its original length it has been compromised and must be replaced."

Savington

iTrader: (31)

If you didn't measure the free length before installation, you need to replace them.

evilrome0

iTrader: (3)

generally if you used them only once you can reuse them, but always measure first. you can also get a reference from arp for their factory length.

240_to_miata

iTrader: (2)

Thanks guys. I'll let my machine shop measure and decide. They may even have new arp studs on hand.

Savington

iTrader: (31)

ARP is very good, but they aren't this good. I typically see a variance of at least ~.005" from bolt to bolt for length, which is enough to make any published reference length worthless for the OP's usage.

If the bolts don't return to within .0005" (that's half a thousandth) of their original free length, they're scrap.

astroboy

iTrader: (18)

IMO if your not sure if you should reuse them you probably shouldn't. Goes with the cheap insurance thing.

psiturbo

iTrader: (1)

Sorry to revive, found the ARP part number 118-6401, for replacement stock rods.

For H-Beam forged, ARP part number 200-6209.

Let me edit a little bit; the sheet is for the hi performance, not M-tuned.

Here is a link for the M-Tuned fasteners.

ARP 2000 5/8 1.6

Found this other site, 2000 ARP torque specs

Just in case the attachment does not work.

Savington

iTrader: (31)

The M-Tuned/SCAT/Eagle/Manley bolts are 1.500" UHL, not 1.600. We have them in stock, $70/set.

psiturbo

iTrader: (1)

Info obtained by Emilio 949Racing.

I will check then, I have not torqued them yet.

Ian

iTrader: (2)

Meh. I just kept torquing the ARPs headstuds down by 5ft/lbs on my old DSM until the head stopped leaking. Who cares if they were at 100ft/lbs, they held 25 psi + just fine on a daily basis.

It's probably best to replace, but I think you can get by if you're willing to accept the risks.

Savington

iTrader: (31)

Torquing ARP head studs past 80ft.lbs on a Miata head is a great way to crack the head.

psiturbo

iTrader: (1)

The digital caliper and the bolt hole thru template states they are 3/8...

The bolt head stamp is ARP 2000 -16.

Savington

iTrader: (31)

SCAT must be using a different rod bolt, then. I just measured a BNIB Manley rod bolt (ARP2000) at 1.500" UHL.