MA70 Fastener / Bolt Specifications / Head Bolts & Studs

cre · 04-23-2012, 07:52 AM

I checked to see if ARP updated their online library to include the fasteners for the MKIII head (which they FINALLY HAVE!!) and they've made a couple changes to the product line.

The rated spec for their head bolts is now 90ft/lbs for head bolts which is the same as the studs when installed with a LOW friction coefficient lubricant (molybdenum or better). Also of note is that while both types of fasteners formerly required ISO size tooling/sockets (which a lot of people didn't realize anyway) the studs formerly used 9/16" 12 point nuts but now use 14mm (very close in size but different nonetheless) and the bolts are 1/2" (I can't find anything about that changing)... A lot of people had a miserable time in the past trying to use 13mm sockets.... I really think the last set of bolts I installed were actually 13mm though, so ARP may have gone fully metric.

If you have an older kit which specifies the lower torque spec I recommend you stick with what the included instructions say. I would not torque OEM bolts to 90ft/lbs, but rather ARP's former recommendation of 75ft/lbs.

As I'm going to copy this to the fastener FAQ thread I'll add that the bore and thread is 12mm x 1.25.

04-23-2012, 07:52 AM	#3
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	I checked to see if ARP updated their online library to include the fasteners for the MKIII head (which they FINALLY HAVE!!) and they've made a couple changes to the product line. The rated spec for their head bolts is now 90ft/lbs for head bolts which is the same as the studs when installed with a LOW friction coefficient lubricant (molybdenum or better). Also of note is that while both types of fasteners formerly required ISO size tooling/sockets (which a lot of people didn't realize anyway) the studs formerly used 9/16" 12 point nuts but now use 14mm (very close in size but different nonetheless) and the bolts are 1/2" (I can't find anything about that changing)... A lot of people had a miserable time in the past trying to use 13mm sockets.... I really think the last set of bolts I installed were actually 13mm though, so ARP may have gone fully metric. If you have an older kit which specifies the lower torque spec I recommend you stick with what the included instructions say. I would not torque OEM bolts to 90ft/lbs, but rather ARP's former recommendation of 75ft/lbs. As I'm going to copy this to the fastener FAQ thread I'll add that the bore and thread is 12mm x 1.25. __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar ---> Last edited by cre; 04-23-2012 at 07:57 AM.