|Everyone seems to be getting caught up in this ARP 8740 vs 2000 deal that Scott posted.
While some of it has some merit, some of it is exaggerated.
"Do you have ARP2000 head studs in your VG engine? You may think you do but you likely do not if you bought them in the last 6 years or so from any Z specific vendors."
Actually the 300zx community has been using 8740 head studs for well over 18-19 years now. It is not a new thing. I ran 8740 studs in my car back in the late 90's and was making over 650 Rwhp at the time.
The ARP2000 bolts were not available from ARP until late in 2013. So all the vendors had to make our own kits using the 8740 bolts. But before ARP finally came out with the ARP2000 kit, everyone with big power had already moved to the L19 kits.(I will touch more on this later)
"The solution to this issue is well known amongst the VG engine builders. We would take the OEM washers and install them with the smaller ARP washers on top and then the nut. This would fix the dimple issue and spread the clamping surface out to an acceptable level. This is where I believe the issue started. Vendors wanted to offer a larger washer but ARP will not modify their kit to include the proper washers."
Hmmmm. This is not something I have ever done. Once the issue with the smaller washers was discovered, I moved to the larger ARP washers. I use the larger ARP washers in both the 8740 kits and the L19 Kits. This is not anything that is new. That has happened for ~5 years now at least.
I have actually taken apart motors with L19 head studs and OEM washers and found them cracked. I have never used OEM washers with ARP studs and strongly discourage it with any ARP Studs. I only recommend the ARP washers in the correct size.
Here is a picture of a cracked OEM washer after removing it from an ARP L19 stud
"Don't be fooled, some vendors actually list the ARP 2000 part number (202-4308) on their website, but when you receive the parts, they will not be in the ARP packaging with that part number on the box."
Not sure who he is talking about since all the vendors I see are not doing that. Unless someone changed recently. I have never claimed my standard ARP kit is ARP2000
"The following image is of the part numbers that all z32 vendors are using in their head stud kits."
This is a 100% false statement. I have used different part numbers for years now. So not ALL z32 vendors.
"Another issue that can sometimes come up is the topic of stud installation.
Some people like to install the studs and back them out a couple of turns to "allow room for expansion due to heat" This is not a good idea for two main reasons. "
Never heard of anyone doing this. Not sure where that info came from.
"The second reason is that on a chromoly 8740 stud, like most have been using, the studs are longer than the ARP2000 studs. This combined with backing the stud out too far will lead to the nut tightening past the end of the threads and can cause a fastener failure under heavy loads due to a lack of thread engagement by the nut."
This is a little bit of misinformation. The stud is longer but that is because it actually seats in the block deeper. If you look at the picture he posted and if you lined up where they level out in the block; you would see that they exactly the same from the block to the bottom of the threads.
See here: LaZy Link
Just push the ARP2000 stud to match the seat point on the bottom threads and the top threads would line up.
"You then want to fully insert the stud into the block and seat it down lightly but snug. In other words, make sure the stud goes fully in and is not stuck on a thread or debris. Then back the stud loose by just a hair to relieve tension."
Weird....just a minute ago we were told not to back it out. Now we are???? Per ARP the stud needs to be installed hand tight. I do NOT recommend backing it out at all. I recommend installing it hand tight and leaving it alone as per the ARP instructions.
" Now I know some of you are yelling at your screens right now saying, "Hey, what about using a better stud like an L19? Why all this talk about ARP2000's?"
Well, here is my answer to that. What I am about to say next has been discussed in great length with the engineers at ARP and they agree with my conclusions here.
If you are lifting a head with a true ARP2000 head stud then you have bigger issues than the hardware! "
This is a great point and I will come back to it in a minute
"Since many VG builders are torquing the L19's to 120 FT/Lb's successfully, there is no reason an ARP2000 can't be torqued to the same level. The ARP 2000 yield strength or the point in where the metal will stretch is 200,000 psi. L19 is 200,000 - 230,000 psi. Both will not reach yield until 125 Ft Lbs of torque or higher. The tensile strength or the point at which the bolt will break is higher on the L19, but both are still plenty high enough that if you ever broke one, it would be due to the engine operating out of an acceptable operating parameter! IE excessive head pressure or detonation etc."
This is somewhat true. The ARP2000 are 220,000 psi and the ARP L19 are 260,000 psi. The 8740 are roughly about 195,000-200,000 psi in the 12mm head stud size. So you only gain 10% by going to the ARP2000 over the 8740 studs but you gain 30% going to the L19 over the 8740 studs.
Here is where ARP lists this: LaZy Link Click on the "ARP Materials" Tab
I recommend going with the 8740 studs up to about 650-700Rwhp and L19 studs if shooting above that(and under ~1500rwhp). I personally don't see a need to chance ARP2000 for not much of an increase in strength. YMMV
"The next best choice for a head stud would be ARP Custom Age 625+ which has a higher yield and tensile strength than L19 and can be torqued much higher than both ARP2000 and L19. But increasing torque on the head studs past 120 Ft Lbs is a problem for the heads anyway as the washer size is not sufficient enough to spread the load out to a point where the aluminum head wont cave in or crack. So a higher tensile strength stud would not really be much benefit to the VG."
I agree and disagree with this statement. It is not the amount the stud can be torqued to but the strength of the stud to keep it from stretching. That is why many other platforms have moved to the L19 head studs over the ARP2000. Many Supra guys, 350z guys, 370z guys, EVO guys, Honda guys, etc... And of course now they have moved up to the 625+ for 1500rwhp+ builds.
"As you can see they show using the L19 for rod bolts and not head studs. This is because a rod bolt will seal the threads into the rods when torqued and this will protect them from moisture. The engineer even said that they have seen boat engines recovered from under water where the rod bolts had no rust/water damage because they were sealed. The same cannot be said for head/main studs. The picture above shows a statement where ARP says "This material is easily contaminated and subject to stress corrosion. It must be kept well-oiled and not exposed to moisture"
As said above, many other platforms have and still use L19 head studs with no problems at all. Until I see a failure using L19 studs, I will continue to recommend them for 650-700+ builds over the ARP2000's. If you are getting water in your oil, you have bigger problems. And until someone shows a failure on an L19 head stud, that will be my go to for big HP builds.
"So to summarize,
if you have a head stud that is stamped ARP, ARP then you have Chromoly 8740 studs. The kits that are being sold are recommending you torque the studs to 90 Ft Lbs. This is a problem as the 8740 studs will reach their yield at 83 Ft/Lbs. So if you torqued them to 90 as advertised, you have stretched the bolts past yield and have rolled or galled the threads on the studs. "
This statement is 100% false. The yield on the 8740 is about 110 ft/lbs. I have been torquing them down on my motors at 100-105 ft/lbs for 15+ years.
The VG30DE Head stud is 12mm. You can see from ARP's site that the 12mm 190,000 / 200,000 (PSI) 8740 studs can go to 112 ft/lbs and the 12mm 220,000 (PSI) ARP2000 studs can go to 125 ft/lbs
Look here: LaZy Link
"What is even more of a surprise to me is that with so many "experts" in our community, not one of them has discovered this issue before.......
Be careful who you trust your engine builds to, for things like this should be an eye opener for this community and a learning experience!"
Weird...I never got a call about this. I have known about the ARP since they were released at SEMA in 2013. I have just recommended the L19 since I didn't think the ARP2000 were enough of an upgrade from the 8740's. Again YMMV. I have actually sold several sets of the ARP2000 studs to customers that have asked for them.
So to summarize,
ARP 8740 studs are 195,000-200,000 psi and can be torqued to 100 ft/lbs to 105 ft/lbs without any issues. They are good for builds up to about 650-700 rwhp(depending on tuning of course).
ARP L19 studs have been used in builds up to about 1500 rwhp without any problems and no failures have been reported to date across multiple platforms.
Just FYI: This is in no way a dig at Scott from Zshack. I just wanted to bring some more info to light since I have received some questions about the differences.
Kyle "Grumpy Bear" Puckett
Import Parts Pro