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Old 08-09-2008, 10:23 AM   #1
pieces
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Default Exhaust to engine stud torque?

Does anyone know the torque specs. for the studs going into the block at the exhaust header?
I can not find this anywhere- Service manual, Haynes, here, general search. As common as header swaps are, I thought this would be easy to find. Maybe current models have bolts instead of stud/nut combo? My car is pretty old (99).
Should I just torque the stud and nut to the same amount as I'm finding for the nut?
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Old 08-09-2008, 01:37 PM   #2
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Old 08-10-2008, 08:48 AM   #3
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^^^^
Really? Where's the stud torque in there? I only see the nut listed. I came across this link before, and just don't see them on there.
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Old 08-10-2008, 09:21 AM   #4
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Just put them in there until they are tight. Torque is WAY overrated, just put them in until tight and you will be find....it's an exhaust stud, not a critical component on the Space Shuttle. The only bolts on Subarus that really need torque are uppipe bolts, coil plugs, and injector rails....everything else, you use your head on.
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Old 08-10-2008, 10:42 PM   #5
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Cool, thanks.
I'll probably go 5-10 lb/ft more than the nut torque spec. on the studs. Seems like a reasonable value.

The torque based on feel is how my dad taught me.
Cars were different then- mostly iron. Aluminum makes me nervous.
I usually use the torque wrench on everything just so I don't over do it on anything. My dad was always a little overzealous- it's hard to loose that. Looking back I really wonder how he never managed to warp a rotor on the tire lugs. He really went off on those.
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Old 11-26-2008, 10:30 PM   #6
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Quote:
Originally Posted by Unabomber View Post
Just put them in there until they are tight. Torque is WAY overrated, just put them in until tight and you will be find....it's an exhaust stud, not a critical component on the Space Shuttle. The only bolts on Subarus that really need torque are uppipe bolts, coil plugs, and injector rails....everything else, you use your head on.

I don't agree. Its a pre-turbo connection so the correct torque is very important to not loose any pressure or vibrate loose into an exhaust leak. "Tight" can very vastly from your small guy to your muscle head. 40N.M is the correct torque.
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Old 11-27-2008, 12:10 AM   #7
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I absolutely think Unabomber is wrong on this one. Torque is very, very critical. Torque is a proxy used to specify the tension in the bolt. Too low and there's not enough frictional force to keep the bolt out of sheer. Too high, and you risk breaking the bolt, stripping the threads, or other consequences such as over-crushing a gasket.

BTW, the correct torque for the engine-to-exhaust studs is 22.4ftlbs.


God knows I've gotten way too familiar with that number in the last 4 days. Stupid headers!
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Old 11-27-2008, 01:14 AM   #8
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i have NO idea where the install torque is for the STUDS.....but for the NUTS...it is 28.9ft-lbs FOR THE TURBO ENGINE

STUDS are installed at the factory and usually not removed...if they DO turn into bolts, re-installing them from the same hole they came out of is critical!!!!!
Torque values in the FSM are for NEW hardware and I have found that using torque values from the FSM on these exhaust parts and used hardware results in leaks and undertorqued fasteners.
I usually increase torque by 10-15% if using used hardware with good results.
ALSO....it is important to snug up these parts like wheel studs are tightened and in steps....I usually get everything(exhaust components) EVENLY tight to 22-23ft-lbs and let it sit for 10 minutes and then final torque.

RE-torquing after seveal heat cycles is also a good idea.

the highest toeque value per the fsm for this section is 28.9ft-lbs....which is pretty low for fasteners of this size
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Old 11-27-2008, 01:47 AM   #9
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Quote:
Originally Posted by Unabomber View Post
Just put them in there until they are tight. Torque is WAY overrated, just put them in until tight and you will be find....it's an exhaust stud, not a critical component on the Space Shuttle. The only bolts on Subarus that really need torque are uppipe bolts, coil plugs, and injector rails....everything else, you use your head on.
Wait...injector rails? Are you talking about the 2 bolts on top that go into the tgv? Why does it matter if those are set at an exact torque? Not doubting you just asking because I recently installed injectors and just bolted them down tight, not at any spec.
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Old 11-27-2008, 04:11 AM   #10
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Quote:
Originally Posted by pDubs View Post
Wait...injector rails? Are you talking about the 2 bolts on top that go into the tgv? Why does it matter if those are set at an exact torque? Not doubting you just asking because I recently installed injectors and just bolted them down tight, not at any spec.
if they come loose....you MAY get fuel under 40+psi spraying around under the hood

bad juju
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