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| Is it true? (Head Gasket Retorque) https://slantsix.org/forum/viewtopic.php?t=17836 |
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| Author: | skraecken [ Thu Jun 01, 2006 9:35 am ] |
| Post subject: | Is it true? (Head Gasket Retorque) |
I got my new headgasket today, (FelPro) it is marked "No retorque". Comments? Thanks |
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| Author: | Doctor Dodge [ Thu Jun 01, 2006 9:46 am ] |
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I always retorque the head after at least one "heat cycle", engine cooling down but not cold and before I do the final valve adjustment. DD |
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| Author: | skraecken [ Thu Jun 01, 2006 11:00 am ] |
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Ok Thanks. |
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| Author: | argentina-slantsixer [ Thu Jun 01, 2006 4:37 pm ] |
| Post subject: | |
Quote: I always retorque the head after at least one "heat cycle", engine cooling down but not cold and before I do the final valve adjustment.
.020" steel gasket would be the same procedure? I got me a set of ARP head and mains stud kit! I'm HAPPY DD  also since I'm taking the head out I'll be porting a little bit more there. Not OS valves Yet! |
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| Author: | Fireball [ Fri Jun 02, 2006 1:43 am ] |
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It is marked for "no-retorgue" for purpose, it is not needed. Just follow the manufacturers info. |
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| Author: | RossKinder [ Fri Jun 02, 2006 7:14 am ] |
| Post subject: | Re: Is it true? |
Quote: I got my new headgasket today, (FelPro) it is marked "No retorque".
I think that's a claim, not a requirement. I've retorqued them and get a lot less additional turn, but still some. There's a fine line between torquing and retorquing. Most people I know of work their way up to torque in steps anyway. Do you want 65 lbs or 64? How fine is the last round?
Comments? Thanks |
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| Author: | Doctor Dodge [ Fri Jun 02, 2006 7:37 am ] |
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A head gasket gets "crushed" hard during the first heat and cool down cycle The head bolts and their related contact points also go through a "strech and settle" process during the first heat cycle. As noted, the thicker composition gaskets (Fel Pro) have more "rebound" built into them so they don't need to be retorqued but if you check the torque after the first heat cycle, you will find that you lost some holding pressure. (usually about 3-5 ft.lbs.) I see a little less "give" with the steel shim type gasket but I still see some. One note is that I do my retorques after the first full heat cycle, and then when the engine is still slightly warm, not "dead cold". There is something different about the amount of torque force needed when the engine is warm vs cold, I find that a warm engine will take a little more "bolt turning" to get to the same torque force used on a "stone cold" engine. DD |
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| Author: | Fireball [ Fri Jun 02, 2006 10:09 am ] |
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Exactly, not needed, but won't hurt anything doing it, but hey who wants to do unnecessary wrenching  I think 3-5lbs accuracy is pretty much impossible to gain with normal tools. It also has a big difference are the threads lubed or not, if yes, with moly grease or normal oil etc. All these have a different input to the actual force. And with alu heads the thermal cycle seems to do more tricks than with iron one, due to better heat transfer in material.
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| Author: | emsvitil [ Fri Jun 02, 2006 3:59 pm ] |
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When you retorque, do you: A: Just retighten the bolt or B: Loosen, then retighten the bolt |
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| Author: | CStryker [ Fri Jun 02, 2006 5:32 pm ] |
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Everything I've ever seen in print says loosen and then retorque, though I've seen/heard of people just giving that little extra twist. Edit: Oh yeah... whatever you do, don't losen them with your torque wrench; that's a great way to throw of your calibration. If you go that route, use a breaker bar or ratchet to loosen a few turns, then use the torque wrench to retighten. |
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| Author: | Dart270 [ Mon Jun 05, 2006 7:12 pm ] |
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I would not loosen first for a modern composite gasket, just tighten up. Can't see any negative to adding twist later. FWIW, I've never had a head gasket problem, and have only bothered to retorque twice, thinking I might have had a gasket problem (didn't after dissassembly). I have r'n'red heads at least 30 times. Lou |
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| Author: | emsvitil [ Mon Jun 05, 2006 7:17 pm ] |
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The thing with torqing bolts and nuts is that once your fastener has stopped turning, it takes more torque to break it loose again. So you might not have enough torque, but don't know it because of the initial stiction. Plus after you've gone thru a heat cycle, the initial stick might be quite high. |
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| Author: | Doctor Dodge [ Tue Jun 06, 2006 9:03 am ] |
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Quote: The thing with torqing bolts and nuts is that once your fastener has stopped turning, it takes more torque to break it loose again. So you might not have enough torque, but don't know it because of the initial stiction. Plus after you've gone thru a heat cycle, the initial stick might be quite high.
This is a good observation and most likely the source of the "loosen", "break it loose" or "back-off and retorque" statements you sometimes see.I usually just tighten the bolt more to get to the listed torque setting but you do have to overcome the "set" the bolt (or nut) has taken in order to get fastener movement and a valid torque reading. Most of the time you go 10 - 20 ft.lbs over the reading you previously torqued at and you hear / feel a "crack" or "pop" as the fastener "cracks loose" and starts moving again. At that point of movement, your higher torque wrench reading drops to the actual torque and you apply additional twist as needed. I run into some bolts that don't "break loose" or "pop" after 10, 20, 30... ft.lbs over torque setting. With these I get out my breaker bar and crack the fastener in the counter-clockwise (loosen) direction, just enough to get movement. Once it "breaks loose", I go back to the torque wrench to apply the correct tightening torque. I do find some over tightened fasteners using this process. Torquing a fastenener is a "feel" and common sense thing, make a mental note on what your target torque setting feels like, no harm in torquing down a bolt in a 'practice part' just to get the "feel". Don't take for granted the torque settings published in non-FSM sources, when in doubt, double check with another source. If for any reason something does not feel right, stop and review the situation, don't 'keep twisting' the fastener. (I have discovered a number of bolts and / or threaded holes, ready to fail, just by paying close attention to how the torquing process "feels". DD |
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| Author: | emsvitil [ Tue Jun 06, 2006 4:14 pm ] |
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Side note on the click type torque wrenches......... Do not loosen the spring all the way when storing. Have just enough tension to keep the internal parts aligned. I found out about this the hard way. I had loosened the spring and stored the wrench. Next time I need it, I set the torque; then when tightening I hit the point of 'it should have clicked by now' and then got a loud snap. But it wasn't the torque wrench, the stud had snapped. It seems that the internal components of the torque wrench got twisted internally (because I stored it loose) and it wouldn't function correctly........ Fixed the wrench, and then it worked fine. Another safety precaution is that I'll do a low click setting before using the wrench to make sure the clicker is working........ |
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| Author: | MitchB [ Wed Jun 07, 2006 9:09 am ] |
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I installed my head using the Felpro gasket and then retorqued at the next oil change. I do believe I did get some additional turn on the nuts. I'm using ARP studs. You MUST back the bolts/nuts off a small amount - say 1/16 turn and then pull to torque spec. The static coeffecient of friction is greater than the sliding coeffecient, so if you just pull on the fastner without first backing off, you may not get any additional movement. Try this the next time you retorque. Mark the fastner's position. Pull with normal torque first and if there's no movement, back off 1/16 and then pull. If you lost any preload on the fastner, then you will see additional movement. Mitch |
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