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Posted: Sat Dec 28, 2013 12:08 pm
by RSR 555
I've never retorqued EJ head bolts. I would recommend just use Hylomar on the gaskets and make sure both mating surfaces and clean and oil free.
Posted: Sat Dec 28, 2013 10:09 pm
by tony
torque to yield bolts can be identified by the shape of the threads. ordinary threads have a sharp edge, torque to yield bolts are rounded as is the thread on the hole, so ordinary bolts cannot be interchanged. this is explained on the packaging of the gasket. the racing hq guys have the heads off the hqs every 2 or 3 weeks and have no problem reusing them, but i would not retorque after a long time, only if i had just rebuilt the motor and run it in, or whatever the packaging recommends. also don't think torque to yield bolts can be retightened as they are already stretched, you risk breaking the bolt.
Posted: Mon Dec 30, 2013 1:08 pm
by RSR 555
Most of the performance engines I have built, I have used head studs so the heads can come on and off multiple times. I wouldn't use stretch bolts for race engines
Posted: Sat Jul 19, 2014 7:43 am
by tony90
tony wrote:torque to yield bolts can be identified by the shape of the threads. ordinary threads have a sharp edge, torque to yield bolts are rounded as is the thread on the hole, so ordinary bolts cannot be interchanged. this is explained on the packaging of the gasket. the racing hq guys have the heads off the hqs every 2 or 3 weeks and have no problem reusing them, but i would not retorque after a long time, only if i had just rebuilt the motor and run it in, or whatever the packaging recommends. also don't think torque to yield bolts can be retightened as they are already stretched, you risk breaking the bolt.
That's not right. Holdens 6 reds have 7/16 unc threaded bolts & are tensioned to 65-70 ft/lbs. All engines that I've seen with TTY bolts have std threads. Only one that I know of off hand that has different thread is one of the MAN Diesel engines has a buttress thread.
Posted: Thu Jan 05, 2017 3:16 pm
by dfoyl
(Bringing this back from the dead)
>DO NOT RE-TORQUE YOU HEAD BOLTS IN ANY EJ MOTOR! or you WILL have a head gasket failure.
>The bolts are what they call 'torque to yield' bolts or 'Stretch bolts' they are a one use bolt.
From reading elsewhere, this is only half correct. They are torque to yield bolts, but they will then retract when removed and can be re-torqued again. Supposedly "some" TTY bolts used by other manufacturers are single-use (example: Dodge RAM Magnum heads for the LA engine, which I have), but the Subaru ones can be re-used with no issues.
(Edit: Sorry, missed page 2 which does sort-of provide confirmation the Subaru TTY bolts can be re-used. I guess the point is that TTY re-use varies from brand to brand)
Posted: Thu Jan 05, 2017 7:31 pm
by Suby Spanner
The general rule is: If the bolts are tensioned, then turned X degrees, they are torque to yeild and should be replaced.
A few manufacturers give specs to measure the bolt for stretch, but this isn't fail proof either.
Twice I've had new bolts fail during torquing, and once many years ago reusing a set.
Is a wasted week end really worth the price of skimping on a few notes for a set of bolts? Not in my world. If there's aftermarket bolts available, I'm using them.
Posted: Fri Jan 06, 2017 8:00 pm
by El_Freddo
Nah re-use the old ones if not over heated. Do it after work on a Monday/Tuesday so it doesn't ruin your weekend!
The HGs and bolts that started this thread did me very well without being retorqued. I had run the engine at 120*C in soft sand at Robe, a few years later froze the blockat Hotham after not reading the new coolant bottle's label close enough. Two years later they gave up after having the AC re-gassed.
I reused those bolts with new HGs and all is well. I'd only do it on a set of bolts that I know have not been over heated. My work is my warranty - if it pops it's on me anyway so I'm happy to take the risk.
Cheers
Bennie