ARP head stud Qs

[brianZortiz]

I am going to buy some ARP head studs for my L28et. I was wondering if the ones for the L28 are the same for the L24 and L26? I am assuming they are but would like to be 100% sure. The other question is how many times can they be torqued down? The reason I ask is because I will be swapping out heads on L26 for know and wanted to use ARP once then if they work throw them on my L28et.

Brian

[BluDestiny]

They are the same. I believe the studs last a long time, and the nuts are what are replaceable? someone please correct me if I'm wrong.

 

For what it's worth, I haven't had to pull the head in my engine for over 25,000 miles.

[kaito]

I dont know the rules for the nuts but I have torqued mine twice. This was before the motor was even run though for mockup.

[Tony D]

I've run 275,000 miles without having to pull the head.

 

It's all in the instructions.

[Z Greek]

I just installed a set yesterday on an engine I am putting together for a Chumpcar. I was actually saving them for my 3.1 project, but the head bolts that were in the L28 looked like they had been at the bottom of the ocean for a week or so, so I broke out the arp's. Guess I'll have to get another set for the stroker! I also have them in the U20 in my roadster, and have never had a head gasket problem since using them (I had been plagued with head gasket issues prior to using them). One interesting note, the nuts on the arp studs I just installed on the L28 are 12 point 12mm. The nuts on the arp studs on my roadster are 12 point 1/2-inch. I fumbled around for awhile before I figured what they were. All of my metric sockets are 6 point, I had to borrow a 12mm 12 point socket to torque the head. FYI.

[Lazeum]

Regarding reuse, you can reuse it as many times as you'd like as long as you're 200% sure they haven't been overtorqued, not corroded & very clean (= no dirt).

Same goes for rod bolts or main bolt but for the cost of a set vs. cost of a rebuild, it is cheap insurance to replace them.

[brianZortiz]

Thanks Guys!!!

[Tony D]

Regarding reuse, you can reuse it as many times as you'd like as long as you're 200% sure they haven't been overtorqued, not corroded & very clean (= no dirt).

Same goes for rod bolts or main bolt but for the cost of a set vs. cost of a rebuild, it is cheap insurance to replace them.

 

I would say, categorically: NO!

 

Why? As explained previously, when using TORQUE as a quantifier of STRETCH/CLAMPING of a joint, you are inherently inaccurate. The breakdown of the TORQUE you see on your wrench is a DIRECT result of FRICTION on the fastener. Roughly broken down as 75% under-head, 15% Thread, and 10% clamping/stud elongation. You are basically looking that only 10% of the TORQUE you read is actually going to CLAMPING.

 

If you change the lubricant, you affect both thread and under-head friction. By decreasing this only 5% (each) you result in 20% of the torque you read now being used for stud/fastener elongation/clamping. THAT IS A 100% INCREASE IN CLAMPING FORCE! It IS a fixed-sum calculation, and is why proper lubrication is critical (note ARP spells out the lubricant to use...)

 

Similarly, a fastener with a nut that is new has specific frictional characteristics. The first time you use it, the threads are DEFORMED. This deformation is referred to as 'burnishing' (at best) and can result in a 2-3% decrease in thread friction. When you consider this fixed-sum equation, a 3% decrease in thread friction results in a 3% increase in clamping force and in effect that is REALLY a 30% increase in elongation or clamping force (13%/10%=1.30 or 30% higher!)

 

Add to this, I know ALL you guys are having your torque wrenches calibrated every 90 days and are within =/-1% of the reading on the scale (more likely 5% if you are lucky...so when you are that inaccurate added to the other items above...

 

For this reason ALONE you should not re-use fasteners. The studs have a much higher tensile than the original bolts, and are far more repeatable because IN HEAD FRICTION IS REMOVED FROM THE EQUATION. The ONLY friction you have to deal with is the Nut, Thread on the top side, and under-nut junction. This is CONTROLLABLE. One of the primary reasons heads (especially aluminum ones) suffer from poor gasket clamping is EMBEDMENT, meaning the stock bolts can cut into the heads and loose the pretension over time. Because the ARP uses hardened washers, substantial ones (as do the stock bolts) and a higher "less stretchy" alloy, they clamp and hold better because of higher initial clamping loads. What you eliminate is the variability of the block cast-iron threads being continually burnished, and due to the alloy in the stud it's threads do not deform. By design the NUT threads now deform, and is the ONLY variable in the process when used with the specified lubricant.

 

Re-use the nuts, introduce variability.

 

As for catagorically saying you can reuse rod bolts, I'm confident I will never do that. EVER. You do, you're on borrowed time. Insane. The ARP rod bolts are far superior for similar reasons as above. I would never re-use a Nissan Stretch-o-Plastic bolt on a rod...EVER. Good luck if you do.

 

I digress...

 

As previously mentioned: GO HERE TO LEARN ABOUT THIS SUBJECT!!!

Edited April 3, 2012 by Tony D

[Ben's Z]

Sorry to hijack. What if you want to plastigauge the rods and mains when re assembling? You wouldn't want to throw away your new arp fasteners just from checking bearing clearances would you? I was going to reuse the bolts for the rods and mains, and go with new OE or arp head bolts. Should I not reuse the old fasteners for the bottom end?

[Lazeum]

despite what Tony is saying, you'll be fine using twice your ARP hardware. You're not going to be close to yield point.

Be sure to always use some lube provided by ARP and follow their torque instructions.

 

(Tony, I'm using calibrated torque wrench while working on engine )