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Engine Specific Info and Questions => IDI Engine => Topic started by: hamradio on March 08, 2011, 11:32:59 am
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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.
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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.
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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.
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I have no idea but why not give it a shot? :-\
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aaaand I just got offered two more AAZ shortblocks.
I'll do this up.
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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.
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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...
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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.
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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.
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hi hammy.
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I'm in for results. Eventually will be looking for studs for my TDI, at some point.
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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?
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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.
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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
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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 ???...
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How did it work out using generic bolts? What did you use? Mcmaster? Part no.s? A question for TheMan53, you say that you sell some bolts, where can I get them. I need headbolts for my AAZ. Thanks, Paolo.
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How did it work out using generic bolts? What did you use? Mcmaster? Part no.s? A question for TheMan53, you say that you sell some bolts, where can I get them. I need headbolts for my AAZ. Thanks, Paolo.
you can get factory bolts for $0.99 at the parts store.
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An update on my buddies '84 I mentioned earlier
the head gasket failed to hold combustion chamber gasses where they belong. ;D
He had about 3,000 miles on it and was running 18-20 psi max, I put his new pump on from Giles thats set up for 30 psi and 5,500rpm....
it was foolish of me to not dial the boost back since its running factory manifolds. anyway it lasted about a day...
Pulled the head off and couldn't find where it had been leaking(normally it pretty obvious in my experience) I actually wrote down the length this time around and i torqued them to 125ftlbs with 15w-40. Im gonna limit boost to 20 psi and report back when he's got some miles on it.
They are Holo-Krome 12.9 socket head cap screws 12mmX1.75 and measure 4.71in under the head. That comes to 119.63mm. Washer thickness is .125in.
Measured an original stretch bolt and it was 4.53in under the head 115.06mm.
I consider it a success regardless of whether the head gasket went. I think with higher power levels ARP headstuds are definitely the way to go and have used them in the past with good results. Hope this helps.
Aaron
P.S.
Thanks to theman53 for makin me go back and look at my shop notes. I had the length wrong. Hope it didn't mess anyone up. It's updated with the new length.
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Any more info on this from people? I'm getting ready to drop the $250 on some arp studs but I can't help but thinking there has to be a cheaper way. Plan on running 25+psi so stretch bolts arnt the answer... Would love to hear if anyone was able to run standard high grade bolts long term without issue?
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Summit has them for under 200 and 10 shipping, I don't know if these are the ones or not...
http://www.summitracing.com/parts/arp-204-4706/overview/
I used unbrako bolts in the bottom end of my build and so far so good. I wouldn't use bolts on the head if I was going to go for big gains, I would used studs and there is no cheap route there.
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Personally used head studs from Raceware; very nice units. :) http://raceware-fasteners.com/ They are very specific about what fits, however, I don't know their current prices.
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http://www.amazon.com/ARP-2044706-Diesel-Volkswagen-Engine/dp/B007FH8WNS
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Guys, I agree with those in favor of the ARP (or any) stud over a bolt - in any application - and every engine I build gets studs. Never had a head gasket failure with the studs. Can't say the same for bolts...
Even NA builds I perform get studs because they're so reliable and consistent.
Bolts are fasteners (provide force/retention from one direction).
Studs are clamps (providing clamping force/retention from two directions).
Just by nature of their design, you can run the highest grade bolt you can find, and never approach the clamping forces of a lower grade stud. It's simple physics.
The only pitfall I can share is the studs DO require re-torqueing at intervals to properly "set" them. After the 3rd re-torque of my ARP studs, they retain >98% of their torque values, which means they vary by <2% across all studs - for the entire life-cycle of that engine. Every studded engine where I've observed head gasket failures was the result of the builder/owner ignoring the re-torqueing requirements from the mfg and failure to 'set' the studs as recommended.
They're more pricey, but bolt performance will NEVER match stud performance, and you truly pay for what you get - or don't get...
If you're after max power, or just plain max reliability and consistency, you can't beat studs.
Just my 2 cents.
Southernman
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The retorque is something I do differently as I use and old gasket and torque them 3 times. Then I go in with the new gasket and do the real torque. After machining most all metals need this, unless you can cryo treat them.
Raceware has had some issues. Rabbit Jockey had some and IIRC so did crazy andy where the stud stripped. I think they used to be great, but now might have some bad batches.
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Just by nature of their design, you can run the highest grade bolt you can find, and never approach the clamping forces of a lower grade stud. It's simple physics.
I'm a big fan of studs, but that's not physics.
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Just by nature of their design, you can run the highest grade bolt you can find, and never approach the clamping forces of a lower grade stud. It's simple physics.
I'm a big fan of studs, but that's not physics.
And your point is...?
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A bolt can maintain the same amount of clamping force of a stud. The idea that it can't is superstition or imagination, not physics.
The benefits of the head studs are that they are reusable, cause less stress on the block threads, and have a fine thread on the outside and so apply a greater clamping force for a given twisting force. The greater clamping force is from the finer thread pitch, not the fact that they are studs vs. bolts.