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Re-torque head bolts?


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43 replies to this topic

#1 Snowman

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Posted 22 February 2004 - 01:34 AM

The FSM says to re-torque the head bolts after warming the engine up when you do HG's. I've heard mention of a special socket to reach the headbolts without taking off the cam cases. Do I need this, or can I just grind down a regular socket? Also, should I do this right away or wait a bit so the engine can go through several heat-up cool-down cycles? And finally, the FSM also says to turn the bolts back 60 degrees and re-oil them before torquing. What is the point in this and how on earth can the oil get down to the threads?

#2 RedLance

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Posted 22 February 2004 - 04:33 AM

I asked this same question about a month ago or so. The general consesus was, that with modern head gaskets you do not have to retorque them. My new gaskets even say right on the package that you don't have to retorque them.

As for the socket should you chose to retorque them anyway, I used a 3/8 drive socket, with a built in u-joint. Got it at sears. I had to also use a couple extensions, and another u-joint. It was a PITA...I ended up also having to loosen the engine mounts, and jack it up about 5 inches, so I could reach a couple of the bottom bolts. But it's doable...

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#3 baccaruda

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Posted 22 February 2004 - 04:46 AM

somebody said they just overtorque the bolts by 3-5 footpounds ( i think FP, not inchpounds) and "never look back", and have had good results. i'd get more info instead of trusting me though :P as i haven't put heads on an engine yet.

#4 asavage

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Posted 22 February 2004 - 01:01 PM

Originally posted by baccaruda
somebody said they just overtorque the bolts by 3-5 footpounds ( i think FP, not inchpounds) and "never look back"

Do you think they retorqued the engines at the factory when new? Nah.

My opinion: mfgrs put that retorque BS in the manual so that when something goes awry they can say, "did you retorque the heads? We told you to retorque the heads."

I'm not retorquing my EA82's heads. I don't know anybody who does (except Lance, I guess). On mine, the gasket surfaces are at least as clean as new, and the castings are now more stress-relieved than new through multiple heat/cool cycles. If it's not going to seal well with a single torque, retorquing wouldn't have helped. Not the official line, but that's my opinion.

Just my .02 (.03 CDN).

#5 Snowman

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Posted 22 February 2004 - 03:53 PM

Okay, this makes me feel a bit better, because I was NOT looking forward to having to jack up the engine and reach in there....

Has ANYBODY EVER heard of HG's blowing b/c of not re-torquing?

It sounds like a b**** to do this, but probably better than replacing the gaskets if they were to go out, so I just wanna make sure.

#6 subarurx

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Posted 22 February 2004 - 05:53 PM

hey guys

the answer to the oil is to allow the head studs to turn better when re-torquing them. just run it down a screw driver and onto the stud's head, and it will tighten better.

as for re-torqueing, I run a EA82T in my leone, which I use for rally's. I have had a terrible time keeping the headgaskets from blowing without re-torqueing at least once (we only run 14psi..so not heaps). also, we over torque them, the book says for the last one at 47, we go to 52 on the last re-torque, and hopefully that will keep em snug. have talked t all sorts of people, and the consensus is to re-torque once only, and some have said up to four times (OMG what **** job that would be...start up, heat up, cool down, cams boxes off, retourque x 4..)

that's my 2c worth.

simon

#7 asavage

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Posted 23 February 2004 - 01:16 AM

Originally posted by subarurx
the answer to the oil is to allow the head studs to turn better when re-torquing them. just run it down a screw driver and onto the stud's head, and it will tighten better.

Studs? Your EA82's got studs? How do you remove the heads with it in the chassis?

Drooling oil under the head of the bolt is best done upon initial assy. You don't want the friction of the bolt's head on the flat washer to influence the turning torque any more than absolutely necessary, but Fuji's 47 ft/lbs figure does factor in some resistance there. Is the turbo motor 47 too? I'd have though that they would have bumped it up a bit.

I use 50. No good reason. But I do tighten them up in three stages, and if I'm doing both sides, I do each stage on each side interleaved, ie 22 on left side, 22 on right side, then 38 on left etc.

as for re-torqueing, I run a EA82T in my leone, which I use for rally's. I have had a terrible time keeping the headgaskets from blowing without re-torqueing at least once (we only run 14psi..so not heaps). also, we over torque them, the book says for the last one at 47, we go to 52 on the last re-torque, and hopefully that will keep em snug. have talked t all sorts of people, and the consensus is to re-torque once only, and some have said up to four times (OMG what **** job that would be...start up, heat up, cool down, cams boxes off, retourque x 4..)

Turbo stuff is different, and for turbo duty, I could see the reasoning for going back and retorqueing . . . maybe! Better would be going to real copper o-ringed heads, but I'll let those who're racing them speak from experience -- Thanks for piping up, Simon!

#8 northguy

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Posted 23 February 2004 - 10:19 AM

Kelly, it's probably just an agreement between the parts manufacturers and the mechanics to make the process such a pain in the @ss that next time you'll pay the money to have a certified mechanis do it. And then, they will only say they did it and pocket the cash.:)

#9 NoahDL88

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Posted 23 February 2004 - 10:49 AM

the theory behind retorqueing is that after the gasket gets compressed it becomes loose again, and a retorque tightens it up again, it can only compress so much so it only needs one retorque, its not a bunch of hooie, its not a warranty voider, theres good science to this.

Oiling the threads puts the maximum torque to the head and not the threads, when torquing a bolt much of the force can be used to just turn it and not clamp it, if the threads are oiled more force is claming force and not turing force and you get a better seal.

#10 Snowman

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Posted 23 February 2004 - 01:00 PM

Okay, I guess I'll pull it in during class today and retorque it just to be safe. I gotta redo the T-belt timing so it's coming in anyway.

#11 Meeky Moose

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Posted 23 February 2004 - 01:12 PM

well scrapdaddytatum put an engine together for a guy awhile back.. overtorqued the head bolts by 3 or 4 lbs.. never retorqued.. cars been driven a good 5k overheated so bad it blew the radiator and hoses.. and guess what.. the headgaskets are still as good as new.. no leakage, nothing..

so if it can survive an overheat that bad, i'd say overtorque a little and forget about it..


did this on my acura too, everyone said don't reuse the bolts.. bah i said, i overtorqued them by 4lbs.. drove it 4k before it was wrecked.. no problem.. lady that bought it is still drivin it aboud.. i imagine she's put a good 4k on it as well...

just my .02

#12 Snowman

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Posted 23 February 2004 - 03:11 PM

Well, overtorquing isn't an option since the engine is already in the car and running:D

#13 Skip

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Posted 23 February 2004 - 03:30 PM

Snowman if you do care to do this here is a descrpition of the socket you requested (see Bill P's post)
retorque tool
Here is a a picture
.Hope this helps some

Posted Image

and the dimensions of the socket before mods

Posted Image

#14 asavage

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Posted 23 February 2004 - 09:05 PM

Originally posted by Skip
Snowman if you do care to do this here is a descrpition of the socket you requested (see Bill P's post)
retorque tool

Sheesh, now I have to supply isometric views and get a better camera just to keep up with the Jones -- er, Bills and Skips!

Obviously, this is the right tool for the folks that gots to retorque. Good job jumping in and providing this info, Skip.

(In that thread, I liked Tolerance2's implication that the intake manifold could crack during retorqueing, if it wasn't loosened! AHAHAHAHA! Just how much movement of the gasket do you think is going to occur by adding two or three ft/lbs!

Torque-to-yield head bolts, as mentioned in that thread RE the Acura, must be replaced for long term reliability. They are designed to provide only so much tension, and you torque them just slightly beyond this. Once stretched, if used again they will not reliably provide the same tension through multiple heat/cool cycles. Fortunately, the EA82 doesn't use torque-to-yield bolts.)

#15 robm

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Posted 23 February 2004 - 09:26 PM

It would be good to point out that torquing through a U-joint is a no-no. The U-joint will change the torque transmitted around the corner. It is a reasonably complex function of the angles involved, and the torque transmitted can vary form 0 - 100%. So don't do it, cut down the socket instead!

By the way, what size was that socket before it was cut? I.e., bolt head diameter. Also, how much of the cut-down depth of the socket is devoted to the square drive of the ratchet, and how much to the bolt head? It is getting to be garage sale season again, time to start looking for stuff like this.

#16 asavage

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Posted 23 February 2004 - 10:29 PM

Originally posted by robm
[B]It would be good to point out that torquing through a U-joint is a no-no. The U-joint will change the torque transmitted around the corner. It is a reasonably complex function of the angles involved, and the torque transmitted can vary form 0 - 100%.

I know! Torque through a constant velocity joint instead of a u-joint ;)

Seriously, for angles of deviation under 10°, I personally wouldn't have any problem with using a u-joint. The further deviation from parallel, the worse the problem.

By the way, what size was that socket before it was cut? I.e., bolt head diameter. Also, how much of the cut-down depth of the socket is devoted to the square drive of the ratchet, and how much to the bolt head?

17mm, I'd think.
The proportions of cut are described in Bill's post :

ground the working end down to considerably shorten it - leaving slightly less than the full bolt head height of inside grip length. Then I ground the other end (the end that the driver plugs into) shortening it a little, stopping just short of compromising the ball detents, and ground that end into a conical shape - around 30° chamfer (30° from the plane that's perpindicular to the drive axis) all around. This gave plenty of relief for the socket to clear under the valve train and fit nicely to the bolt heads with room to spare.



#17 grossgary

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Posted 03 January 2006 - 11:14 AM

does anyone know what happened to the picture of this retorque tool mentioned above? dimensions, instructions, etc?

#18 WJM

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Posted 03 January 2006 - 02:26 PM

SUBARU socket.

#19 grossgary

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Posted 03 January 2006 - 02:34 PM

hhhmmmm, i stopped in the local dealer and they couldn't locate it. said they'd try and call me back. been about a month, nothing.
got the part number?
i saw it posted in a thread before but can't find it right now.

#20 grossgary

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Posted 03 January 2006 - 02:38 PM

i got this but the thread never says EA81 or 82 or other:

Subaru Part Number: 499987200

i think that's an EA82, it doesn't say but i found an EA81 with a different part number, so i think it would have to be for an EA82.

i'll get a price sheet.

I myself am ordering a EA82 head bolt socket...its abuot $5 more to get it from tihs company than SUBARU...as subaru doest have ANY service tools anymore...they contract thru this company now it seems...

I'll get a price sheet hopefully.


did you ever get one will?

#21 Subarian

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Posted 03 January 2006 - 02:45 PM

So, Snowman, did you retorque? And how much of a pain was it?

I've built a lot of engines, Chevy, Olds, Ford, Toyota, and Subaru, and I've never retorqued. I've never had a HG fail, even on some fairly built (Olds and Chevy) engines. But I've never built a turbo or diesel engine, so those might need to be retorqued.

I guess the bottom line is that if it gives you peace of mind, it might be worth the effort.

#22 grossgary

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Posted 03 January 2006 - 02:47 PM

snowman, i dug up a really old thread so response may be sparse.

#23 Snowman

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Posted 03 January 2006 - 03:27 PM

So, Snowman, did you retorque? And how much of a pain was it?

I've built a lot of engines, Chevy, Olds, Ford, Toyota, and Subaru, and I've never retorqued. I've never had a HG fail, even on some fairly built (Olds and Chevy) engines. But I've never built a turbo or diesel engine, so those might need to be retorqued.

I guess the bottom line is that if it gives you peace of mind, it might be worth the effort.


I never did, and never had any problems in 20,000 of use. That's on a naturally aspirated, basically stock engine, which is not naturally prone to HG issues. If I was building a turbo motor that I knew was going to be run hard, I would definitely retorque the bolts to avoid any risk of blowing the gasket or damaging the heads.

#24 211

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Posted 03 January 2006 - 09:45 PM

If you really want a science to what a bolt is actually doing during and after you torque it here goes.

This is actual data taken from a test I did a while back at work. We strain gaged a set of transmission bellhousing bolt heads and torqued them to 28lbs/ft.
As you can see there is an immediate load placed on the bolt the second we begin to tighten it. Keep in mind the gages were placed on the head of the bolt not the shank; so if you can imagine, the shank of the bolt is wanting to pull through the head. In essence, the fastener is in tension, or stretched, when it’s installed. This stretch is called its “preload”,
...but everyone knows this much.


What you don’t see is once we’ve reached out desired torque value (in our case it was 28lbs/ft) there is a “yield”. This is shown in the data curve. 28lbs/ft was achieved just under 1100uS (microstrain), then immediately yields to 850uS. Also what you don’t see (and is not shown in this particular data file) is the “relaxation” that occurs over a period of time, in my case I recorded data on this load for 24 hrs and saw a relaxation of about 10-20uS (negligible in most all cases). You can see a little relaxation in the image below but not much, the time history on this data file is just over 8 min.


Posted Image



So, what’s proven is there is a yield, and a relaxation that occurs after the fastener has reached its torque value (commonly referred to as “bolt stretch”). This is the reason for re-torque.

However, does this mean it’s really necessary to pull your motor, remove the camblocks and retorque your heads? I don’t really think so. Here’s why. Regardless of bolt stretch or yield or whatever you want to call it, we've subjected the fastener and joint (gasket) to an excess clamping force, this “clamping force” is the torque value (determined by some engineer somewhere). In theory, the fastener will not see any additional load or yield as long as the force pulling the joint apart is less than the preload, not gunna see it by “warming up the motor”.You may however, see it by "NOT" warming up the motor! Like when the engine's cold and you peel away from your house late for work at 7:00am (but those are expansion-rate issues which cause warpage, not really where we're going here).

Along with the test we did, we also recorded a series of warm-up and cool down sessions; what we found was rock-solid strains across the board (no change among 12 gaged bolts). We then took the vehicle on the track to record durability events and found no change in bolt strains. When we did see strains from the track show through the bolt heads, were when we loosened them up to 12lbs/ft. But by then the transmission, in effect, was “dangling” from the fasteners.


Add to this, the composition in today’s gaskets have improved dramatically since the mid 80’s.

…plus, just to be ultra sure, I emailed FelPro and asked and they said their gaskets do NOT require a retorque :clap:

LOL, I guess I could've just said that and saved you all from that bit of bolt-load theory.


#25 WJM

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Posted 04 January 2006 - 12:49 AM

That is very interesting. Thanks.




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