Arp Rb26 Head Studs (202-4207): Following Torquing Procedure Of Nisssan Or Arp?

[Behind Horizon]

Hello,

I bought some ARP head studs (202-4207) for my RB26. However I am a bit confused as I am not sure which torquing procedure I shall follow best.

The Nissan torquing procedure for head studs is:

1. Tigthen to 29NM
2. Tigthen to 108NM
3. Loosen to 0 NM
4. Tighten to 25-34 NM
5. Tigthen to 103-113NM

However the ARP manual states:

Following the manufacturers recommended torque sequence tighten the nuts in three equal steps to 105 ft lbs / 142 NM
with ARP ULTRA-TORQUE FASTENER ASSEMBLY LUBRICANT.

So should I use the Nissan torquing procedure but torque to 142NM instead of 103-113NM in step 5 or should I follow the ARP procedure (three equal steps to 142NM)?

Don't tell me to ask ARP regarding this case as I wrote them already two messages (one 10 days ago, another one 5 days ago) and no one bothered to reply to me.

So their customer service doesn't seem to know the solution.

Thanks!

[r33_racer]

If the engine was built from scratch, as in torque plate bored/honed with the studs at their ideal torque etc etc then I would use the arp tensions as they make the stud and know what torque is required to achieve proper stretch plus the machining was done to suit that tension.

However, if you are just putting some studs in your standard engine to replace the bolts for whatever reason then I would go no more then the standard torque. The problem you might have is the bores will be stressed in a different manner now and they will most likely go out of round (even if only slightly) with more torque pulling the head down harder.

[Adriano]

is the hread pitch on either end of the stud different, if so(i think they are)torquingto nissan specs with lubricant will increase the headgasket crush by about 50%

[scotty nm35]

I used ARP specs but I admit, my bore is floating so doesn't suffer from the 'out of round' associated with solid blocks. Clamp the sucker down tight was my motto, 96nm ftw.

[GTScotT]

I followed ARP specs on 2 motors I have used them on, but did tighten then slack off process for OEM gasket. No torque plate hone on either motor, one with MLS HG other with OEM crush type. Both motors since faultless.

I prefer the ARP method as the OEM method is intended for two things: to crush the gasket and then torque, and to allow bolts to stretch. The ARP studs stretch far less and are reusable, so the torque settings are not relevant and 3 steps is better for even torque when not expecting bolts to stretch. If you are using an MLS gasket the tighten then slack off process is also redundant as you don't need to crush the gasket before going for final torque.

In the case of using an OEM gasket go to 30/65/100nm, then loosen off and go 3 increments of 47nm. I wouldn't be afraid to go 3 increments of 50nm (50/100/150) to allow for tool slack.

If using an MLS probably stick to 4 increments of 47nm if you have good tools.

[Ben C34]

it's not just to crush the gasket the multi stage. It is to also seat the head of the bolt onto the surface below it, in order to get a more accurate torque reading. Can't remember the exact link, but it was from an unbrako catalogue (they make high tensile bolts)

[DCIEVE]

How do you figure the ARP's stretch less?

I would follow the ARP method as closely as possible including lube type etc. The relationship between pre-tension and torque is obviously very sensitive to friction but also things like tightening speed etc.

[Behind Horizon]

I will be using a Metal Head Gasket. I removed the head to seat the valves, the block will stay untouched. GtScotT, you mean three and not four increments of 47NM (3*47NM=142NM)?

Still there doesn't seem to be a consensus here regarding this matter...

is the hread pitch on either end of the stud different, if so(i think they are)torquingto nissan specs with lubricant will increase the headgasket crush by about 50%

The final torque recommended by Nissan is lower than the one by ARP. So how come that the head gasket will be crushed more?

[Ben C34]

What he is getting at (I think) is you need to think of clamping force and torque differently. a finer pitch thread will produce more clamp force at tge same torque setting as a coarser thread. just like if you dont lube up the bolt, it will lose alot to friction and produce far less clamping force.

[Ben C34]

Sorry, should have quotes adriano there

[GTScotT]

How do you figure the ARP's stretch less?

I'm just putting things into simple terms. The ARP's are not torque to yield like the stock bolts are, so the easiest way for me to have described WHY they take more torque to the OP was to say that they stretch less. While that may or may not be entirely accurate it is a reasonable way of thinking of it. ARP themselves describe stretch yield to be 5 thou as a rule of thumb, so if considering that as a base the ARPs must stretch less at a given torque, to take more torque than the stock torque to yield bolts and not exceed 5 thou.

Clearly I am not taking the metalurgy of the bolt or its elasticity into consideration as it is hardly important in answering OPs concerns.. The point is that the specs for torquing them are higher than stock and OP should not be concerned.

I will be using a Metal Head Gasket. I removed the head to seat the valves, the block will stay untouched. GtScotT, you mean three and not four increments of 47NM (3*47NM=142NM)?

Still there doesn't seem to be a consensus here regarding this matter...

Yes I do mean 3 increments of 47nm. So in the case of using a MLS HG I would sit the head onto the block and use the factory torque down order, 47, then 94, then 142nm. Double check the last increment and make sure you are pulling the tool towards you, slow. Do not push the tool away when torquing. Steady your body and use the motor and your strong arm to pull towards.

[DCIEVE]

I'm just putting things into simple terms. The ARP's are not torque to yield like the stock bolts are, so the easiest way for me to have described WHY they take more torque to the OP was to say that they stretch less. While that may or may not be entirely accurate it is a reasonable way of thinking of it. ARP themselves describe stretch yield to be 5 thou as a rule of thumb, so if considering that as a base the ARPs must stretch less at a given torque, to take more torque than the stock torque to yield bolts and not exceed 5 thou.

Clearly I am not taking the metalurgy of the bolt or its elasticity into consideration as it is hardly important in answering OPs concerns.. The point is that the specs for torquing them are higher than stock and OP should not be concerned.

Your comments about stretch to yield are very misleading. Broadly speaking the point of using higher grade fasteners is to increase pre-load. ARP are a very high grade fastener (up to 1500MPa UTS) so to hit the higher pre-load the torque is higher. Two bolts of differing grade will stretch the same amount for a given pre-load (assuming equivalent geometry), it's just that the higher grade fastener is capable of a higher pre-tension before you exceed the proof stress. A rule of thumb for stretch ignores the biggest factors driving elongation which are 1) length and 2) pre-load/stress.