Head stud torque and aluminum blocks

[go302]

Just spoke with the man John Mihovits to get some input on my build and talked about overbore and torque specs. Anyway, I remember some people here having issues with head studs on their aluminum blocks. He torques his down to 85 ft*lb on aluminum blocks, not 100 like arp states. Just passing this along so everyone can stop cracking their block and distorting it all to shit!

 

[702GT]

Is that using ARP Ultra-torque lube? I've read some of his posts on other forums regarding torque specs on ARP head studs. I still haven't come to a conclusion for myself on the matter. What about those running an iron block/aluminum head? 85 ft/lbs or 100 ft/lbs? 15 ft/lbs can make a world of difference in clamping force.

 

[go302]

using arp lube. Didn't talk about iron blocks. But said he was running 11:1 compression 65 psi at 85ft*lb using arp lube.

 

[thump_rrr]

JDM recommends 70 ft/lbs using ARP Ultra-torque lube.

 

[swflastang05]

100 ft/lbs works fine if you do it correctly. You must make sure there's sufficient clearance b/w the bottom of the stud threads and the head and you cannot allow the stud to turn as you torque it down. This is done without using ARP lube on the bottom of the washers. I learned this the hard way but it works.

EDIT: You must also not allow the studs to bottom out

 

[05moneypit]

I went to 85lb with ARP lube on the advice of another mod motor builder after ruining at least two engines at 100lb. Using an iron block now, two years of racing and have blown as much as 25lb of boost in it with 10.5:1 CR and no issues.

 

[go302]

100 ft/lbs works fine if you do it correctly. You must make sure there's sufficient clearance b/w the bottom of the stud threads and the head and you cannot allow the stud to turn as you torque it down. This is done without using ARP lube on the bottom of the washers. I learned this the hard way but it works.

EDIT: You must also not allow the studs to bottom out

One of the reasons he stated that 100 was too much for aluminum blocks was due to it distorting the mains. I wouldn't go past 85 after talking to John. I used 100 on my first motor with no ill effects but a few main bearings had some abnormal discoloration on the edges. Were the head studs the cause? idk

 

[go302]

I went to 85lb with ARP lube on the advice of another mod motor builder after ruining at least two engines at 100lb. Using an iron block now, two years of racing and have blown as much as 25lb of boost in it with 10.5:1 CR and no issues.

85 seems to be the magic #

 

[loots06]

Could the same be used for TTY hardware?

 

[weather man]

[PHOTOB][/PHOTOB]

Could the same be used for TTY hardware?

No! Follow the manual for Ford TTY bolts.

 

[05stroker]

I'll keep my fingers crossed, I have always done 100 Ft LB with oil and the studs not bottomed out in the block.

 

[05moneypit]

I'll keep my fingers crossed, I have always done 100 Ft LB with oil and the studs not bottomed out in the block.

100lb with oil is probably about the same as 85lb with moly. Oil is higher friction than moly.

 

[702GT]

100 ft/lbs works fine if you do it correctly. You must make sure there's sufficient clearance b/w the bottom of the stud threads and the head and you cannot allow the stud to turn as you torque it down. This is done without using ARP lube on the bottom of the washers. I learned this the hard way but it works.

EDIT: You must also not allow the studs to bottom out

Do you apply lube to the stud after you've seated the washer to achieve this or are you lubing just the nut threads? I've always seen a few studs turn when torqueing heads down on the initial torque sequence. This is applying lube to the stud and then dropping the washers on them. After the initial sequence they don't turn, but I always back them out 2 rotations from bottom-out.

 

[Dubstep Shep]

So my question in, why does ARP specify 100 ft-lbs if it isn't ideal?

 

[s8v4o]

So my question in, why does ARP specify 100 ft-lbs if it isn't ideal?

It may be ideal, for the stud anyway. I'm guessing that it may be the same part number for iron and aluminum engines but I don't know for sure.

 

[Dubstep Shep]

It may be ideal, for the stud anyway. I'm guessing that it may be the same part number for iron and aluminum engines but I don't know for sure.

I'd buy that.

I've been looking at how to increase the head clamping force. I've been considering going to a larger stud size but I'm not sure if that would help.

 

[swflastang05]

Do you apply lube to the stud after you've seated the washer to achieve this or are you lubing just the nut threads? I've always seen a few studs turn when torqueing heads down on the initial torque sequence. This is applying lube to the stud and then dropping the washers on them. After the initial sequence they don't turn, but I always back them out 2 rotations from bottom-out.

I use just a very small amount of oil on the lower stud threads, maybe a couple drops max. Then ARP lube on the top threads, bottom & inside the nut and top only of the washer, making sure the surface of the head where the washer seats is super clean as well as the bottom of the washer. I'm talking brake cleaner spray clean! There still may be a couple studs that turn a bit when you bring them to max torque, but not enough to cause any problems, especially when you back them out a couple turns, like you stated. I was one of the dumb asses that cracked my previous block in three places by doing this incorrectly in the past, a tough and expensive lesson learned, one that I will never forget, but the above procedure works. I have tons of respect for Mihovetz too, I just learned from another source.

 

[05moneypit]

This is mine from a couple years ago. I did a thread here on it but it is worth revisiting. I was so curious as to what went wrong that I took the block to work and cut it in half through the bolt hole where the crack was.

The stud can not bottom out in the bottom of the hole because there are not enough threads on the stud, it will bottom out on the top of the hole first. The second picture shows the crack is below the stud. Literally what happens when it is over torqued is you pull the block apart.

I agree with what swflastang05 says about not using lube on the bottom of the washer and believe that would make a difference. However when I talked to Al in tech at ARP he said to use lube on both sides of the washer.

I used a different brand of moly lube that we have at work (Molykote GN paste) and according to ARP that was the issue because it is much more slippery than ARP moly lube. I have used the Molykote for many years without a problem on many other engines.

Like I said earlier, I went with 85lb and ARP lube at the advice of another engine guy. Is that the correct torque? No but it has worked for two years and countless passes.

 

[go302]

Good info here. Money pit, what is your entire procedure for head stud installation?

 

[Dubstep Shep]

Moenypit, do you have any more pics of how your block cracked?

I'm wondering if it's the torque or the clamp load that's causing the blocks to deform.