Technical Question about re-torquing cylinder heads.

I have just got done doing a roadside (Beaver Dam, WI.) head gasket change. This after the left side let go about a month ago.
So both are now done.
The factory does not have a recommendation to retorque, nor do they specify to Not retorque.
Soooo, should I??
I think it would be prudent, so the question really is:
Do you simply pull on the torque wrench while the engine is cold, or do you loosen each bolt and then retorque it. Further, do you loosen all then retorque, or one at a time??
Lastly, does it matter the composition of the head gasket (it's composite), or if the head and/or the whole engine is aluminum??

Thanks, because I have never known the answer to this question.

Cosmo

 

retorquing head bolts went out of style about 40-50 years ago, didn't it? I've never done it, after the first engine I overhauled in 1975.

 

If a newer car with "use once" head bolts, I'm not sure if I would.
Old style (or good quality) full strength head bolts, I always run one heat cycle, let the engine sit overnight and retorque.
Cheap insurance..!

Mike

 

Use a non hardening sealer on the headbolts and retorque after motor has been up to temp and completely cooled off. I went many years without retorque. One spring I fired up the motor and had a leaky gasket. When I redid the gaskets I retorqued them at no extra cost to me....

 

This is a question that never seems to get answered...

 

Do you simply pull on the torque wrench while the engine is cold, or do you loosen each bolt and then retorque it.


I have never loosened bolts to re-torque... I simply re-run the proper torque sequence, after a heat and cool down. . . Has always worked for me, but I am not an expert . . .

Lynn W

 

Re-torques (whether cylinder heads, or anything else) are just making sure the fasteners haven't loosened. Set the wrench to the minimum torque specified within the range, and torque slowly and evenly till it clicks (or reaches the specified value on the scale). That is, in the tightening direction.

If you were to loosen the fastener and then re-tighten, the retorque requirement would never end!

Check for any movement of the fastener, there shouldn't be any. If it does move, you could try torquing everything to the maximum value within the range, and check again after the proper interval. Usually there will be no movement, or very little, if the proper sequence and hardware was used to begin with.

 

To seal an engine up right you run it under a load at 2500 rpm for a half an hour or so, re-torque the head bolts when it is hot then back together and see where your timing is etc

Then you are ready to blast it and make some good numbers

DND

 

I fired up my 301 SB Chev for the first time after I built it 33 years ago and the new head gaskets (composite items) started weeping coolant along the lower edge, I re torqued them by loosening and torqueing the head bolts one at a time in the recommended order, they have now resealed. So yes they can loose tension but that depends on what type of gasket you have. JW

 

What does timing have to do with cyl. Head torque??
So if you check the torque when hot and they cool the torque changes to a lesser number generally. Or am I reading this wrong, never heard of checking torque when hot.
Well of course I usually deal with under head valve engines that require a re torque at least 3 times minimum when stone cold. As we know real engines don't have valve covers. Ha Ha .

 

Only if it's a flathead. HRP

 

I have never re-torqued a head gasket unless it was a shim gasket.

 

ya them shim ones ... e specially if -n- ya stacked em...

 

Re-torquing the heads was standard procedure when I worked on diesel engines in heavy equipment. It would be done right away after getting the engine up to temperature, checking for and correcting any leaks or anything else that needed attention. Putting the engine through a full round of performance tests, checking high idle, low idle, stall speeds, turbo boost pressures, blow-by, oil pressures, maybe even fuel pressure in some cases (depending on make/model of engine). When all of that is done we'd shut it down and while still hot we would re-torque the heads. Each bolt, one at a time, backing off about half a turn then back down to specified torque. I've always done it on every gas engine I've built too, it's just the way I was trained.

 

The head gaskets we get today are compressible as most of them are composite type gaskets. If you torque them down run the motor and then loosen them (even one at a time) you loose that compression. That is a bad thing. I personally don't believe there is any reason in the world to "RE-Torque" a head gasket once it is installed correctly, but if you feel like you just have to do this do not loosen the head bolts so that you can retighten them, that just doesn't seem to make much sense.

 

Well, if you've ever done it you'd find that you almost always pick up a few more degrees of rotation before reaching full torque. If you don't loosen the bolt that won't happen. Don't like it, don't do it, that's fine. But there is "sense" to the procedure.

 

No it still doesn't make any sense, if you torqued the head bolts to a correct and specific torque setting and then by loosening them you get more rotation ( your words) it would seem to me that you also have changed something, and altered the original torque setting.

 

Utilizing studs vice bolts and some of the newer anti-siezes helps improve the confidence in single time torquing. The ARP ultra anti-sieze improved a consistent stretch on rod bolts, so I believe the same for clamping head studs. I think this is ARP's selling points....... being directed for use by TF teams and short turn arounds.

 

No, you haven't changed anything or altered the original torque; there is settling and mating of the surfaces that occurs in the initial operation after assembly that results in a loss of torque. The re-torque is performed to get that tension (stretch) back on the bolt.

 

This is ARP's current recommendation:

Do I need to re-torque my head bolts or studs?
If you follow the ARP installation instructions, there should be no need to do a re-torque. However, it may be necessary under certain circumstances if the gasket manufacturer’s instructions require it, particularly if a fire ring has been installed. ARP recommends not doing a re-torque on a hot engine.

They (ARP) use to recommend torquing fasteners 3 times to diminish the effect of friction on the fastener working surface when reading torque values. Their "ultra" brand supposedly reduces
that friction.

 

I know with the torque to yield head bolts which is likely not what you are referring to or even using while working on this engine, they are a one time use bolt that stretch and you throw them away for a new set if you take it apart again. In my opinion, they are just another throw away item like most of the new stuff out there and is why I tend to lean towards old anything with an engine.

I worked in a machine shop for 5 years and also did maintenence on anything that came in through the doors. We would fire up an rebuilt engine and go through the tuning, looking for leaks, etc first. It was a standard practice that we did of checking bolt torque on what was accessible such as intake manifold bolts, water neck bolts as the gaskets seem to compress once heated up through a heat cycle. We never took the valve covers back off to retorque head bolts except for a 70 Buick 350 that was leaking coolant out between the driver's head and block. The gaskets we used were the blue felpro or Rol gaskets which are mostly composite type now. In my own opinion, most of your gaskets now won't require retorque if you put it back together correctly. It's too costly to have to take apart an engine to retorque a gasket as part of the procedure for repair. Gaskets have improved over the years and unless it's leaking, I wouldn't go through the effort to retorque it. Just my thoughts on that.

If you do check the torque, I would not back off the bolts. I would check the torque with the torque wrench to see if they move and if they click at the specified torque, move on to the next one. Now I did come across some head bolts that using liquid Teflon pipe sealer is a must in some applications. Coolant or oil seeping up between the bolt threads and block would weep out by the head of the bolt which the pipe sealer stopped. Most of the new stuff now almost has to be minimal for error proof by others doing repairs on it. Now putting a thin layer of silicone on these new gaskets with the oring built into the plastic gasket flange is a recipe for disaster but that is another story. I don't claim to know all. Just saying what I have come across.

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Retorque during a hot condition is not going to produce the same results as assembly when it's cold during the repair. When you take apart whatever you are working on, do you want to work on it when it's hot at 210*? Most likely not as you probably don't want to burn yourself or deal with hot parts. Retorque when it's cold would be the more logical time to do the procedure. Heat changes dimensions in different materials.

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if you're putting aluminum heads on a flathead, retorque several times...

 

Just retorque to specs after the first warm up. You can do it while it's warm or cold on a flathead. Never loosen them to retorque them unless you absolutely have to do so. Personally, I let the heads and motor cool down and then retorque.

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Let's make sure we're talking out of the same dictionary, even if the original post is a specific type of fastener, many modern designs use "torque to yield" bolts, these are one-time-use only (technically) that are torqued to a specific value, and then tightened further, not with a torque wrench but a certain angle or number of degrees. If you want to get fancy, the bolt is stretched to the center of its modulus of elasticity. The short answer is, don't fuck with it. At the very least, don't loosen it.

Other fasteners use embedded nylon plugs, have deformed threads, or use additional safety devices like Loctite. These should never be loosened either.

Maybe "retorques" is a misleading term. It's properly a torque check.

 

A bit old thread but still good subject...
This applies to cars with cast iron heads/block and reusable head bolts. I wouldn't retorque a "stretch bolt".

FelPro says retorque isn't necessary, but I do it. I've read to crack the bolt loose, then retorque - note where the wrench starts and how much extra you get. You can try retorque without backing off (to see if they're REAL loose), but if you don't crack bolt loose first, there's 'sticktion' and it won't retorque properly or at all. Do one at a time - about 1/16" turn (to crack loose) shouldn't affect so much (like causing head to warp). I always did this cold. Last time I got maybe 1/8 turn on each bolt - this on '67 Pontiac 400 with 95 ft lbs torque, std FelPro blue gaskets after cleaning bolt holes with a tap, wire brushing bolts, and with a drop of oil on threads. I use a clicker type torque wrench in 20 ft lb increments (checking it against beam wrench, because I still don't trust clickers so much), then do final torque with beam torque wrench.

Last night I checked head bolts on a '72 Pontiac 400 (same gasket type/prep as above) while still warm after running it the first time, and it broke loose at about 65 ft lbs. (yikes!) - on 2 bolts... I didn't retorque these, but will check again when it's cold. When warm, things change... bolts lengthen, bolt holes expand (though so does the bolt, but there must be an expansion difference between bolt steel and cast iron).

Ah.. just saw this - guy also said to lube the underside of bolt head (which I've never done but will in future). He says to retorque cast iron heads warm, but aluminum cold.
http://www.aa1car.com/library/ic697.htm

 

ran a blown 509 Donavon had head gaskets weeping called a friend (an old time engine builder), he said put a fuse around the perimeter of the head gasket ( copper) . the fuse was sewing thread laid down and held in place with grease or coppercote. never had to retorque all season. ran 19 lbs of boost with 11 to 1 compression

 

Yes! There is a certain amount of "loosening" that happens when the "sandwich" in motor is heated the first time, necessitating a re-torque, especially with studs.

Some motors can't be re-torqued if the mechanic didn't use a non-hardening thread sealant, as in the case of SBC & BBC.

Also, by loosening the bolt (or nut) a few degrees you overcome the stiction under the washer face of the nut or bolt on the re-torque and you get a more accurate squeeze on the gasket.

If you have blind holes, the threads should be lubricated and the washer face should be lubricated.

I like to re-torque head gaskets if I can.

 

Back in the early 80's, I had to replace the heads on a 400 small block and used one of those cheap rebuild kits that contained shim head gaskets and I was too cheap to buy the perma torq gaskets. Put the engine together and it ran great until the next day when I got up and tried to start it. Both head gaskets had leaked and it filled the cylinders with antifreeze and it hydro locked up. I pulled the heads and replaced the gaskets with the perma torq type and never had a problem again.

 

^^^^^^^^^^^^^^^Double Ditto w/Aluminum Heads^^^^^^^^^^^^^