Grade 12.9 bolts in place of ARP studs.

[hamradio]

So, being the cheap bastard I am, I'm looking into getting some grade 12.9 bolts or studs from mcmaster-carr instead of buying ARP studs, for an AAZ.

I've got ARP studs in my 11mm 1.6, love them, but I have a damned hard time paying $120 for some bolts.  Mcmaster has grade 12.9 bolts in the appropriate size for roughly $2/ea.  Tensile strength of an ARP stud is reportedly 190,000 psi, min tensile strength for a 12.9 bolt is 174,000 psi.

I realize ARP has actual r&d into their product in order for it to perform properly in an automotive environment, but does anyone see anything glaringly wrong with using generic 12.9 bolts?  I can't imagine they'd be worse than OEM stretch bolts, or even the OEM non stretch in a 1.5 or early 1.6.

I got this idea from an e30 forum, where it seems popular to use generic bolts in place of OEM on turbo builds.

I'm pretty sure I'll give this a go.  If they fail, eh, I'm out a head gasket.  If they work, I've saved $100 and come across a cheap trick to do with my future diesels.

[Bugsy_malone 666]

Its funny, but I found a set of ARP bolts on ebay, high price as you say but they only list them at 180,00psi, but say they have been tested to 200,000psi!

What I would probably suggest is find your local stockist of gen vw parts, give them a call and ask if they know the rating of stock head bolts as presumably it should be written on them.

I'd go look at my bolts but the cars not really local enough for me to just look at right now to see if anything is written on the bolts.

You say about being cheap as well, surely a set of stock headbolts cant be that expensive? they are designed to do a job, how much extra stress is on them in you application?

You may find that ARP studs/bolts and stock head bolts also have slightly different qualities about them other than their tensile strength compared to stock bolts.

[hamradio]

I don't want to buy stock stretch bolts, as I'm planning on running 25-30 psi into an aaz.

I think that would be a good test to see if mcmaster bolts would hold up.

[rallydiesel]

I have no idea but why not give it a shot? 

[hamradio]

aaaand I just got offered two more AAZ shortblocks. 

I'll do this up.

[clarkrep]

Torquing them is a grey area. Can't really use what works for ARP studs because they have a different thread pitch on the upper part than the 12mm SHCS.
I'd be interested to know what you end up doing.

That being said,I did this three weeks ago on my buddy's 84 jetta TD. I had them left after I tore an engine apart(almost threw them away before I realized what they were) (:
I chased the threads in the block with a tap because I was a little paranoid of cracking the block. Good thing I did too because they were within a thread or so of bottoming! Torqued them to 90 ft lbs with 15w-40 engine oil and they have not caused any trouble in 1500 miles.

[maxfax]

Interesting idea indeed...  Although as said torquing would be a grey area..  Although there are charts in various repair and machining manuals that list torque specs as per the size and threads of the fastener.. That could be a good starting point...

[clarkrep]

Also, I ground the tap so it would cut threads as near the bottom as possible. I should have written down the length of them...sorry.
Its runnin 18-20 psi of boost with a t3 and a fiber gasket fyi.

[theman53]

The SPS Unbrako 12.9 that I sell works fine. I have some in my mains and they are holding. McMaster is the devil The unbrako is a better grade 12.9 10% more strength. Usually more expensive, but worth it to me.

[Digital K]

hi hammy.

[8v-of-fury]

I'm in for results. Eventually will be looking for studs for my TDI, at some point.

 

[mystery3]

I got this idea from an e30 forum, where it seems popular to use generic bolts in place of OEM on turbo builds.

e30tech I'm guessing?

[nathan_b]

my guess is less than 1/10 people need head studs... With a metal hg and a good block and head it IS no problem running 20lbs or more of boost.

[R.O.R-2.0]

So, being the cheap bastard I am, I'm looking into getting some grade 12.9 bolts or studs from mcmaster-carr instead of buying ARP studs, for an AAZ.

I've got ARP studs in my 11mm 1.6, love them, but I have a damned hard time paying $120 for some bolts.  Mcmaster has grade 12.9 bolts in the appropriate size for roughly $2/ea.  Tensile strength of an ARP stud is reportedly 190,000 psi, min tensile strength for a 12.9 bolt is 174,000 psi.

I realize ARP has actual r&d into their product in order for it to perform properly in an automotive environment, but does anyone see anything glaringly wrong with using generic 12.9 bolts?  I can't imagine they'd be worse than OEM stretch bolts, or even the OEM non stretch in a 1.5 or early 1.6.

I got this idea from an e30 forum, where it seems popular to use generic bolts in place of OEM on turbo builds.

I'm pretty sure I'll give this a go.  If they fail, eh, I'm out a head gasket.  If they work, I've saved $100 and come across a cheap trick to do with my future diesels.

1.5 head bolts are grade 12.9

[sdwarf36]

ARP bumped up their testile strength numbers across the board on all their studs. The ones we use in VW's went from 180,000 to 200,000 lbs. So a place may have old stock kicking around. If you have a package of moly thats white, its the older stock. If its blue (labeled ultra torque) its new stock. (also notice the torque went up-its a "firmer" moly.) I ordered 2 sets a couple of months apart-one came in old-the other new. Dunno how many Ford Cosworths get rebuilt a year ...