Jun head studs

[Super_Dude]

Does anyone know the tensile strengh of the jun head studs? I'm using rb25 head studs with my rb30 and Im concerned standard arp studs arent going to hold up.

If any of our vendors have a relationship with jun, it would be awesome if could find out. I will buy a set if they are stronger than arps.

[NismoS-tune]

Last I checked while shopping, ARP headstuds were used without issue on 1000hp engines like yours. Have you tried the special ARP studs?

[Super_Dude]

1000hp drag cars. 700whp track cars can have issues. The hi octane r34 blew a headgasket at superlap and they switched to l19 studs. They are running 12mm rb26 studs so l19's are cheaper. Rb25 l19s would be custom made and cost $1200+.

I dont want to switch to 12mm studs because i think it would be trading one problem for another. So tougher 11mm studs it will be.

[333]

I vas under the impression that jun studs were arp.

[Super_Dude]

They probably are just resold/marked up standard arp's. They are 3x the price of arps so they might be higher end stuff. I'm not expecting them to be l19 but there is lots of grades they could be.

[333]

super dude I will check with a buddy that has a set of jun studs and I will compare them with the set of arp's thaat I have.

[jdms13rhd]

I vas under the impression that jun studs were arp.

yeah, I was too. I know they brand their head gaskets from cosworth. Also their rods. I dont buy jun.

Im sure, with a proper gasket and a flat polished deck, you wont have issues with arp studs. If you went 12mm studs the head would need to be modified as well. Im not even sure it can be done? Plus, you can buy another gasket for a lot less than buying fancy custom studs. Id rather have a back up head gasket since it is a rare shot to loose one from stretching an ARP stud.

[Super_Dude]

It's a 26 head so m12 would work just fine. It's the rb30 block that doesnt like the big studs.

About just having a backup gasket. I would rather just solve the problem than fix it repeadly. Worse case scenario, I drive to event after paying my entry fee, blow the head gasket, have to get a tow home, payed for an event I didnt race at. Then I could be out more money than just buying studs in the first place

[jdms13rhd]

It's a 26 head so m12 would work just fine. It's the rb30 block that doesnt like the big studs.

About just having a backup gasket. I would rather just solve the problem than fix it repeadly. Worse case scenario, I drive to event after paying my entry fee, blow the head gasket, have to get a tow home, payed for an event I didnt race at. Then I could be out more money than just buying studs in the first place

Ahhh. I read wrong above. I only looked up and read the part that said using rb25 head.

With RB26 head and RB30 i drill and tap the block to suit 12mm studs. Everyone does and its safe to do so. No different than rb26. same 86mm bore anyways. plus, there is an extra 40lbs of iron on the top of a RB30. They're a stronger block. Should cost around $120 for a machinist to do so.

I've used rb26 head on rb30's before and if you DID use rb20/25 studs, they are 10mm and the block to head dowels are smaller on rb20/25. Not sure how the head will center itself on the block properly as there would only be those 10mm bolts.

Anyways, I just never done a 26 head with the smaller bolts. You should read up if any other guys have done that safely before you go and spend money on the wrong bolts. But from what I get and have done, I'd suit the block for the head always. Same with the restrictors as well!

[NismoS-tune]

If I ever go RB30, the 12mm studs would be a must (some guys even use 12mm on the 26 bottom end. Hopefully, that's not the case and my next project engine in a 302R rather than a small displacement engine

[Super_Dude]

Rob recommends and uses 11mm rb25 studs in all his motors. His reasoning is the deck of the rb30 isnt as thick as a 26. The extra clamping force may distort the deck of the block. Also, you can't properly drill 11mm to 12mm because the threads won't be complete.

[JNS Performance]

L19's will not be over $1000, I currently have sets of the RB26 L19s for $600. If you would like me to check I can contact them and get pricing on a set.

Not sure what the setup is with Skylines as I have never checked but I know alot of the Supra guys tap to use 1/2" headstuds. Some even get 1/2 L19 studs which have been proven on numerous 1500hp 2J's. Maybe check out that route?

[Super_Dude]

They already make rb26 l19's and they arent one offs. Rb25 would have to be custom one offs. Im talking to arp about other materials but the biggest cost is because they are only making one set.

If you can get better pricing that would be awesome. I would gladly pay extra for the piece of mind.

But back to the original topic, does anyone know the tensile strengh of the jun studs? Does anyone even know if jun has someone that speaks english there? Then i could just email them

[jdms13rhd]

Rob recommends and uses 11mm rb25 studs in all his motors. His reasoning is the deck of the rb30 isnt as thick as a 26. The extra clamping force may distort the deck of the block. Also, you can't properly drill 11mm to 12mm because the threads won't be complete.

Yeah, I heard rips use the 11mm's. But so many other builders using the 26 studs with no problems. You can chase the threads as they are the same pitch. I guess either way it would be fine. I never heard of a block warping or a stud ripping out before. I only see people say that could be an issue with 26 studs, but never seen evidence of it. I just figured since the 26 bolts are thicker/stronger and easily available that it was an option for you.

But if your in contact with Robbie, just ask him what studs he is using as he has the fastest rb30's and advocates 11mm studs. I never heard of them pulling or warping a block either, but maybe I havnt looked hard enough. I suppose its all a possibility, but they are iron blocks. Maybe the weakness is from the water jacket/frost plug cavity being lower on the 30 but I dont see it causing issues as hundreds of rb30's have been suited with 12mm with 26 head, and with that many, you would think you can find at least one picture or one thread on that it causing damage.

[DreadedFist]

My general rule of thumb is that if Jun is selling something for $3,000, everyone else is selling the same thing for $1,000. And if Jun is selling something for $3,000, it's probably made by Cosworth and then tripled in price.