Upgraded 1UZ Head Studs

[6BOOST]

Hey guys, I know lextreme sell the head stud kits for the 1UZ, not trying to outdo them at all, but have found another option for forced induction guys that would like some extra head clamping over the standard 10mm bolts. In my opinion, I'm suprised more people don't have issues with head sealing, as the heads are very big, wide and flat, pretty large bore, and small(for its size) 10mm head studs.

For those that don't know, teh factory head bolts are 10x1.5mm thread. The bolts I'm fitting to mine are RB25 nissan 6 cylinder studs. They are actually 11x1.5mm, all that is needed is to fit them is run a 9.5mm drill through the factory holes, and retap with an 11mm tap. As teh thread pitch is teh same, whats left of the original thread will guide the tap into its new home at 11mm, and yes, I'm a machinist by trade, have done this on other applications before. It would also pay to run an 11.5mm drill through the head to give alittle clearance on the studs. Length is spot on, and if 2 people get together, you could purchase 3 sets and share/split the extra set to get enough studs. Cheap, and slight upgrade to head clamping for minimal effort.

Cheers...........................6BOOST

 

[1ndecent]

Sterling idea, 6BOOST!

 

[ozvenom]

very interesting!!

will have to look further into that maybe we can buy them together i have trade accts and may be able to get the price down even further.
question Are the rb25 bolts torque to yeald or reusable??
I have used the 1uz bolts but you realy only get one go at reusing them and i have never realy felt that they were fully torqued down .If you have ever torqued a head down and had a bolt go weak right at the end you would know what i mean.
I am interested you can pm me if you like chances are we may know each other.
Regards oz

 

[6BOOST]

I'm not using standard RB25 head bolts but RB25 ARP head studs. These are completely reusable, I'd prob change them after 6-8 head removals though just to be safe, but they are not torque to yield. I think with ARP moly lube they recommend about 70ft/lb of torque compared to 10mm ARP studs at about 60(stock diameter. I have 1 set here, if you would like a set yourself, we can purchase another 2 sets, 1 for yourself, and go halves in the second box and have a full set each.

We also do know each other, I purchased a rear sump off you about 6 weeks ago for a 1UZ and am putting it in a Series 3 RX7, I had the engine in teh back of a white hilux and got your details of the guys at Asian Auto just around the corner. I'll get around to bringing the front sump back one of these days:tongue2:.

I've also figured out a way of tapping them dead straight on a assembled engine. I'm going to silver solder/braze the 11mm tap to a 12mm rod, set it up in the lathe and get it true, then machine the complete shank down so the whole thing runs true. Then just drop it through each head bolt hole with the head bolted on, the head will hold it true, then remove the head after each one and suck out any swarf or metal. Sounds bit entailed, but can't think of any way to tap it dead true with the heads off unless you use a machining table, then you can't do it to an assembled engine. Happy to lend you the tool when I'm done, I bought the tap last week

If you'd like to chat, pm me your number(lost the one I Had) and I'll give you a call.

Cheers...........................6BOOST

 

[turboteener]

I have to ask, why you beleive the 10mm head stud can't handle the HP level you are shooting for? I know of many boosted engines making 200hp per cylinder that don't have a problem with a 10mm head stud.

 

[6BOOST]

Firstly, its not a factor of outright believing the 10mm studs won't handle the power, its the fact we can't buy the kit here in australia, we have to order it from lextreme. Secondly, its about 50% dearer to purchase a set of lextreme studs than if 2 of us purchase 3 sets and share the second set. Lastly, I don't know of ANY 1UZ's making 1600hp, there is rail in wa making 1400ish, and it has 1/2" head studs. The 1UZ has big wide flat heads, with only 4 bolts per cylinder and large spaces between bolt holes, clamping force is low on the 1UZ, and stretched bolts and blown head gaskets are semi common, I know of 3 people that have done it, you simply can't compare the head clamping ability of 1 engine to a completely different engine.

While it would be far simpler for me to buy a set of lextreme studs, and I will use some of his main studs in the future, I have a set of RB25 ones already left from another engine we didn't use them on, and I have a 11mm tap, so its pretty cheap, simple and straightforward for me.

6BOOST

 

[turboteener]

Oh, OK. Sometimes I forget you guys down under can't get lots of the stuff we can.

 

[Lextreme II]

11 mm is a great upgrade. Here in American we have a kit for 7/16". However, either way you still need to drill and tap and that is alot of work. I think machine shop charge around $300-$400 for the process. Secondly, dont forget you will need to open up the heads too (holes from 10mm to 11 mm) Please see www.lextreme.com/allgo.html for 7/16" stud upgrade.

 

[dweinhart]

Sorry, I know this is back from the dead but noone has 2zzge studs. I am going to try the RB25s but ARP list two part numbers. Can anyone verify the correct one?

Head Stud Kit

Nissan 2.5L RB25, 6-cylinder
Kit #: 202-4309​

Specifications
Socket Size(s)	5/8 12pt, 3/16 Allen​

or

Head Stud Kit

Nissan RB20, RB20DET, RB25, RB25DET
Kit #: 202-4301​

Specifications
Socket Size(s)	1/2 12pt, 3/16 Allen​

 

[Zuffen]

I would think the 2nd set are the ones to get.

They list the DET engine and that tells me they will see more compression than a standard RB.

 

[dweinhart]

but are the length and thread correct is the question.....

 

[dweinhart]

so the dimensions of the 1uz head bolts are M10 x 1.5 x 110m with a tensile strength of about 180,000.. I am going to try to find a manufacturer to provide some thing similar. In the meantime the ARP 674-1011 M12 x 1.5 x 100m are chromoly 8740 and although they aren't studs would probably be a cheap upgrade if bolt holes are enlarged. Do you think the 10m shorter will make a difference since they are wider?

 

[dweinhart]

M10-1.5 x 110mm Socket Head Cap Screw Grade 12.9 | K.L. Jack

www.kljack.com

These are industrial grade bolts rated 12.9 instead of oem 10.9 with a M10 x 1.5 x 110m
Min. Yield Strength (MPa): 1,100
Min. Tensile Strength (MPa): 1,220

Not quite ARP but definitely a step up over stock bolts and only cost $30 + shipping for 25 of them.
If anyone can give me the length of their ARP studs I would much appreciate it

 

[dweinhart]

Also found these. You will need 3 and then cut to size. 170,000 tensile strength but no hex cap

https://www.grainger.com/product/FABORY-Fully-Threaded-Rod-25DL67

I have taken the plunge . I purchased 3 meters and matching 12.9 nuts. I will let you know how long they last.

 

[dweinhart]

UPDATE: Industrial Grade bolts rated 12.9 are still weaker than automotive grade 10.9. Do NOT buy

 

[blinkerfluid]

UPDATE: Industrial Grade bolts rated 12.9 are still weaker than automotive grade 10.9. Do NOT buy

Thank you good sir!