Head Studs

**ywgbandit** · 11-18-2014

I have been doing a lot of reading about head studs and I am more confused than educated!. From what I have read the ultimate option is the ARP 625's, but OMG they are over $1K...they should be the best and I can see if you are running some wild HP & boost. I am looking for reliability running the basic RaceMe that only has 3 tunes, 40hp Economy, 80hp Tow and 120hp Street. I am only using the 40hp & 80hp settings on a deleted engine that is stock otherwise. My question is this: Between the ARP 425's @ around $500 and the A-1 Extreme duty H-11 HD @ around $700. which is the better head stud? Is the A-1, H-11, HD worth the extra money?

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**DRD** · 11-18-2014

Originally Posted by ywgbandit

I have been doing a lot of reading about head studs and I am more confused than educated!. From what I have read the ultimate option is the ARP 625's, but OMG they are over $1K...they should be the best and I can see if you are running some wild HP & boost. I am looking for reliability running the basic RaceMe that only has 3 tunes, 40hp Economy, 80hp Tow and 120hp Street. I am only using the 40hp & 80hp settings on a deleted engine that is stock otherwise. My question is this: Between the ARP 425's @ around $500 and the A-1 Extreme duty H-11 HD @ around $700. which is the better head stud? Is the A-1, H-11, HD worth the extra money?

H11's are supposed to compare to 625's but that's just hear say on my part. I don't have any experience with them. I'm a bit old fashioned and I prefer ARP fasteners because they have been in that business successfully for many years. I think 425s are sufficient for your application but 425s are made of a material that does stretch a tad over time and I'd recommend a check on their torque after a period of time after the install. 625s are made of a super hard material and once your torque them, you can pretty much never have to worry about them stretching over time.

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**ywgbandit** · 11-18-2014

The H-11, HD are pretty much in between the 425's and 625's as far as tensile strength. They are not supposed to have as much stretch as the 425's. They will most likely be more critical for not exceeding the torque value as they are apparently made of a harder, more brittle material. I would think an advantage of this is not having to re-torque as frequently.

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**Wildkarrd RRD** · 11-18-2014

There's a thread on here from me pretty much doing the same research and asking the same questions... ended up going with arp 425's (2000, same thing) and having them over torqued per the ARP rep. (Iirc final torque was 165ft/lbs) they will stretch and flex which still means if something HAD to give, your head gasket will still pop but otherwise less chance of any other damage. The H11s I've heard are good studs, but since they won't stretch they'll snap then you gotta figure out how to get a broken stud out of your block

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**DRD** · 11-18-2014

I've got a set of 625s for myself that I'm going install before too long. They have the appearance of stainless steel but I don't what the actual alloy is. I know from other customers trucks, they don't rust...so they gotta have a high nickel content at least. That being said, they are very hard and have a high tensile strength. Under a straight pull, such as a head fastener application, they should be very very strong and should not break. Now if they were pulled upon with a heavy side load under torque, they may snap. ARP recommends 150 lbs of torque on 625s but says you can go 160 lbs at your own risk. I'm gonna go 153 lbs with mine because my torque wrench has a + - 3 lb error.

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**Wildkarrd RRD** · 11-18-2014

Originally Posted by Double R Diesel

I've got a set of 625s for myself that I'm going install before too long. They have the appearance of stainless steel but I don't what the actual alloy is. I know from other customers trucks, they don't rust...so they gotta have a high nickel content at least. That being said, they are very hard and have a high tensile strength. Under a straight pull, such as a head fastener application, they should be very very strong and should not break. Now if they were pulled upon with a heavy side load under torque, they may snap. ARP recommends 150 lbs of torque on 625s but says you can go 160 lbs at your own risk. I'm gonna go 153 lbs with mine because my torque wrench has a + - 3 lb error.

You'll strip out the block long before the studs break on a straight pull. The fun part and kicker to these studs (I found out anyway) is that they have a "recommended torque" a " you can torque" that you can get a hold of easily. Then the "mechanics torque" which is my way of saying a shop that happened to know one of the reps fairly well got the specs as far as what the shear point and where ARP themselves set the torque themselves at final testing. The figures listed with the studs are only right around 60-65% of where the stud can safely be and still have a cushion from shear

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**DRD** · 11-18-2014

Originally Posted by thewildkarrd@doublerdiesel

You'll strip out the block long before the studs break on a straight pull. The fun part and kicker to these studs (I found out anyway) is that they have a "recommended torque" a " you can torque" that you can get a hold of easily. Then the "mechanics torque" which is my way of saying a shop that happened to know one of the reps fairly well got the specs as far as what the shear point and where ARP themselves set the torque themselves at final testing. The figures listed with the studs are only right around 60-65% of where the stud can safely be and still have a cushion from shear

Good info Drew! What I'd like to know, and something few talk about, is what point with stud torque/clamping force would the studs themselves start to distort the cylinder? I know with the many high octane gassers I've built, you torque plate the block before honing the cylinders to get a round cylinder while the block is under head fastener torque load.

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**Wildkarrd RRD** · 11-18-2014

Let me see if I can get some numbers, or at least ask Parks if he can get them for me tomorrow.

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**ywgbandit** · 11-19-2014

I am going to go with the A1 Technologies, H-11 head studs, but not over torque them. They are made of a more brittle material, but in a tension load they should be less likely to take a permanent stretch. I don't want to risk stretching them past their recovery point and actually ending up with less clamping pressure. I will also do the 4 torque to full value cycles before the final torque to make sure the stud threads and washer surfaces are smooth as possible to eliminate the possibility of a skewed torque reading because of drag torque. This should give a very equal clamping load on each fastener and keep well within the stretch limits of the studs.

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