It appears I stretched some ARP head studs...

[BigBeans]

I put a new head on my car not too long ago. Everything was spotless, torqued in sequence to 86lbs with ARP Moly lube, decked block and head, cometic 1.6mm MLS, and a set of standard ARPs that i reused.


About 2,500 miles later, i was going up a steep hill wide open at 7600rpm in 4th gear (a lot of load on the engine), running 30psi, when i had what appeared to be a head gasket failure. I had to baby the car a few miles to get to an area where it was safe to stop and wait for a tow. At first the coolant temp starting rising quickly, and then started dropping again right before i parked it.

There was no significant knock so i didn't know what happened, but based on the coolant in the exhaust, intake runners, engine bay, and incredible cloud of smoke, it was pretty obvious.

I tore it down today and the head gasket looked like new. There's literally not a mark on this thing, and no signs of detonation anywhere.

At this point i decided to measure the studs for stretch. I can't find the spec for stud length anywhere on this site, ARPs site, or any of the common vendor sites. All i could think to do is measure them against the new L19s i bought to replace them. I would assume the length should be the same for standard studs and L19s, but i'm not positive.

The results were, on average, .006 longer for my used standard studs. The L19s were all 4.302-4.303, while my standards were all about 4.308.


The motor has low mileage but was built several years ago, and the studs haven't seen much above 32psi or torqued too tight, so i'm very surprised to see this. They were reused once, and retorqued after the motor was heat cycled based on Cometic's instructions.

I have two questions:

First, are standard ARPs the same length as L19s, and what is the spec?

Assuming they are the same, my second question is, has anyone seen these stretch at such a low power level?

My street tune is 30psi with a safe tune, about 52-53 lbs/min and i doubt it makes more than 430-440whp on this tune.

HKS gasket, L19s, and a few other goodies are going in...time to make more power.

 

[SpawnedX]

Killer of quality parts! L19s are the same length, ARP sells a different version for shorter studs.

 

[BigBeans]

Killer of quality parts! L19s are the same length, ARP sells a different version for shorter studs.

Thanks for the confirmation.

I don't abuse my car by doing stupid things, but i definitely enjoy having the hammer down regularly.

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[DSMopar]

As an aftermarket automotive engineer I can tell you with almost complete certainty the tolerance on the length of those studs is probably larger than .006".... further more, I seriously doubt that motor could generate the pressure/force to stretch those studs.

 

[sniver]

Another concern might be your torque wrench. Is is a quality item from a reputable vendor? Or is it 15yrs or and never calibrated.

From what I have gathered arps only deform in overtightening situations, and that if they do lift to blow under tons of boost, they don't deform. That's what a couple local builders opinions are.

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[Burnett03]

I doubt you stretched the studs. However I believe you overtightened them.

 

[white92talontsi]

I doubt you stretched the studs. However I believe you overtightened them.

He did stretch the stud's.
He did over-tighten them.

 

[BigBeans]

As an aftermarket automotive engineer I can tell you with almost complete certainty the tolerance on the length of those studs is probably larger than .006".... further more, I seriously doubt that motor could generate the pressure/force to stretch those studs.

Well, i measured 4 new studs and all were within .001. I measured 4 old ones and they were within .001 also, except they were about .005-.006 longer.

If i cracked the head or block, i'd have coolant in 1 cylinder, not all 4, so it had to be a head sealing issue because there's coolant everywhere. All over the engine bay, in all 4 intake runners, and throughout the exhaust.

The head gasket is completely perfect, and there are no signs of detonation anywhere.

The head was retorqued after i ran 25 psi for a week or so. Then i turned it up experimented at around 32 and settled at 30. I don't know the whp, but it could spin all 4 to 60+mph.

I made 370awhp on 25psi with 7* timing because the guy who tuned it pulled all the timing based on 0.4 counts of phantom knock. First log i did on the street i could tell it was phantom knock, i added 5* of timing and turned up the boost 5psi and reached the real knock threshold. I don't think the car would be making much more than the mid 400s, but who knows, it definitely got a lot faster.

Another concern might be your torque wrench. Is is a quality item from a reputable vendor? Or is it 15yrs or and never calibrated.

From what I have gathered arps only deform in overtightening situations, and that if they do lift to blow under tons of boost, they don't deform. That's what a couple local builders opinions are.

Sent from my Droid

I definitely think the TQ wrench could be an issue.

The ratcheting mechanism in mine started acting up a few weeks prior, so i borrowed one from a friend.

It was a Snap-On click type, but i don't know its age or when accuracy was last checked. Probably a long time ago because he's not in the business anymore.

 

[DSMopar]

Well, i measured 4 new studs and all were within .001. I measured 4 old ones and they were within .001 also, except they were about .005-.006 longer.

And? that just means the blanks they used to produce that batch were .005-.006" longer. Furthermore if you 'lift' a head at WOT, you're going to blow the head gasket. Keep searching for the problem.

 

[BigBeans]

And? that just means the blanks they used to produce that batch were .005-.006" longer. Furthermore if you 'lift' a head at WOT, you're going to blow the head gasket. Keep searching for the problem.

I just had a 40 minute phone call with an excellent tech guy at ARP.

We went over EVERY detail of the install, retorque, usage, and failure.

What he told me was, the comparison to the L19s is not valid because their batches vary by a few thousandths. He said the cost to make the manufacturing any more consistent than it already is would price them out of the market. Makes sense.

After reviewing every detail, he said it's highly unlikely that this failure was due to over-torquing the studs.

He thinks cylinder pressure exceeded the capacity of the studs. What he basically said was, if the motor got slight detonation, combined with the combustion pressures of a high boost engine, it's possible that it could overcome the studs without damaging anything else. If the detonation was brief, the engine could show no symptoms but the brief pressure spike could be too much for the studs. Maybe that's what happened, maybe it was some other factor. At this point i don't think i'll ever know.

I'm just going to put the new gasket and L19s in, and assuming no problems arise i'll retune it with meth, bump up the timing, and hopefully that's the end of it.

The one thing he did say, which seems way off, is the torque spec for L19s with ARPs Ultra Torque Lube, is 130ft/lbs. That seems way too high for our engines.

What are people torquing L19s to?

A buddy is bringing me a freshly calibrated Snap-On Digi, so we can eliminate that variable. I'm going to test it against the other Tq wrench and see if the first one i used is miscalibrated.

 

[DSMopar]

What he told me was, the comparison to the L19s is not valid because their batches vary by a few thousandths. He said the cost to make the manufacturing any more consistent than it already is would price them out of the market. Makes sense.

Holy shit what a concept!

Maybe that's what happened, maybe it was some other factor. At this point i don't think i'll ever know.

No, you did not lift the heads briefly and spew a bunch of coolant everywhere... you either cracked something or blew the headgasket. Keep in mind not every blown headgasket is extremely obvious.

 

[BigBeans]

One quick thing to note, this isn't an ARP bashing thread. I've bought ARP fasteners several times, their customer service is excellent and i will continue to buy their products whenever i can.

Holy shit what a concept!

I don't work in fastener manufacturing. Until i spoke with someone who did, i had no idea what the expected variance between batches was.

I said in the opening post that the only reason i resorted to measuring them against a new set was because i can't find a spec for length...according to your last thread you couldn't even find a spec for torque, Mr. Smartass.

No, you did not lift the heads briefly and spew a bunch of coolant everywhere... you either cracked something or blew the headgasket. Keep in mind not every blown headgasket is extremely obvious.

The ARP tech guy knew the power output of the car, and said even slight detonation could stretch these studs at this power level. Do you really expect me to take your opinion over his?

Let's think logically for a minute. As i already posted, there's coolant residue in all 4 intake runners. That means a crack is basically impossible, and the head gasket would have had to leak across the entire length of the engine. I'm not sure how that could happen with adequate clamping force...

 

[sniver]

I have two tips;

Get it back together, and watch it boost along happily, sounds like you have a decent setup. I'm curious to see if there are any differences between the torque wrenches.

And two, its better to ignore morons/smartasses/trolls than it is to acknowledge them. They want conflict, so pretend like they are invisible, it eats them alive.

 

[twicks69]

I have my L19's torqued to 115 ft/lbs. 30/60/90/110/115 torque sequence. I did have two L19's stretch during installation once, and ARP replaced them free of charge Next Day Air.

I did torque-check my head studs two times after installation after several heat-cycles.

I was also using ARP ultra-torque assembly lube and a Mitsubishi MLS head gasket. Holds my current peak of 52psi no problems.

 

[BigBeans]

I have my L19's torqued to 115 ft/lbs. 30/60/90/110/115 torque sequence. I did have two L19's stretch during installation once, and ARP replaced them free of charge Next Day Air.

I did torque-check my head studs two times after installation after several heat-cycles.

I was also using ARP ultra-torque assembly lube and a Mitsubishi MLS head gasket. Holds my current peak of 52psi no problems.

Thanks.

I'm going to try the HKS "Stopper" 1.6mm. We'll see if it's worth the premium price tag. I tend to think i paid for the name...

I'm not sure if i should go as tight as 115. Ultra Torque requires a bit more than Moly, but 115 is A LOT of torque. On race fuel and meth, my setup is probably capable of an absolute max about 200whp below your posted dyno numbers, so if i can go a little lower and avoid the problems associated with those very high torque specs, i'd prefer to do so.

Any thoughts or recommendations?

 

[twicks69]

Don't even waste your money on the HKS gasket. Get the block deck nice and clean, have a fresh decked head checked for flatness, install a new/clean Mitsubishi OEM MLS head gasket, L19's with ultra-torque lube and at least 100 lb/ft torque. They are made to handle it.

Thanks.

I'm going to try the HKS "Stopper" 1.6mm. We'll see if it's worth the premium price tag. I tend to think i paid for the name...

I'm not sure if i should go as tight as 115. Ultra Torque requires a bit more than Moly, but 115 is A LOT of torque. On race fuel and meth, my setup is probably capable of an absolute max about 200whp below your dyno numbers, so if i can go a little lower and avoid the problems associated with those very high torque specs, i'd prefer to do so.

Any thoughts or recommendations?

 

[BigBeans]

Don't even waste your money on the HKS gasket. Get the block deck nice and clean, have a fresh decked head checked for flatness, install a new/clean Mitsubishi OEM MLS head gasket, L19's with ultra-torque lube and at least 100 lb/ft torque. They are made to handle it.

The block will be spotless, and the head was resurfaced a few thousand miles ago but i'll take it to a machine shop to be sure it's still flat.

I already have the HKS so i might as well put 105lbs on it and hope for the best.

This is why we cant have nice things...

Not sure what you mean?

 

[sniver]

Not sure what you mean?

I think he's talking about the cult like following of specific products, and the shunning of anything else. no?

 

[twicks69]

If you got it, run it. I was just saying that the MLS gasket with L19's is more than proven in our application.

The HKS piece is a very nice head gasket, just over double what a MLS head gasket costs from Mitsu.

 

[Rob10_99]

Are you sure it wasn't knock that killed the headgasket?

 

[twicks69]

Could have easily been from heat soak causing knock, or the head lifted. If it was under load for extended time both issues would be possible factors in the coolant passing the head gasket and entering the combustion chamber. It happens.

 

[BigBeans]

Could have easily been from heat soak causing knock, or the head lifted. If it was under load for extended time both issues would be possible factors in the coolant passing the head gasket and entering the combustion chamber. It happens.

It was a very high load situation, i'd been having a little fun so the motor was hotter than usual, and would have been more likely to pick up a bit of knock than usual.

At this point, the only thing i can really do is upgrade the components, run a cooler t-stat, and tune a little less aggressively next time so the car won't have any issues taking boost in longer durations/abnormally high load situations.

 

[twicks69]

Sounds like a smart gameplan. What thermostat did you have in the car when this happened? Did you have any datalogging capabilities to see your actual coolant temperature?

 

[BigBeans]

Sounds like a smart gameplan. What thermostat did you have in the car when this happened? Did you have any datalogging capabilities to see your actual coolant temperature?

The current thermostat has been in the car since i bought it a couple years ago. I'm pretty sure it's an OEM t-stat.

My coolant temps are usually around 200 at cruise, 210ish if i'm really on the throttle on the street, and i've had it up to 220 on the dyno. I was not logging when this happened, unfortunately.

I have a 170* going in with the new stuff, so i'm hoping things will stay under 185 in most situations. It's got a Fluidyne Al radiator which seems to keep temps stable, but at a higher plateau than i'd like with the old T-stat.

 

[twicks69]

Are you still running ethylene glycol-based anti-freeze or are you running water with Water Wetter and a small amount of anti-freeze?

The 170-degree T-Stat will definitely help.