Head Nut Torque - Hot of Cold

[Ron/IA]

In a current thread discussing head gasket repeatedly blowing; I have noticed most are doing re-torque when the engine is cool. However, on pages 289 and 375 of the service bulletin book, it states to re-torque when engine is thoroughly warm.

So, which way is correct? Since the service bulletins were written, has there been a reason to do the opposite (torque cold instead of warm)? Other printed information I have don't state one way or the other. In fact, some material I have don't even mention re-torqueing after initial installation (which I know better).

I may have started a long winded and opinionated thread, but I would really like to know.

Ron/IA

[ford3]

i torque mine after getting engine warmed up and then cooling down, after warming an engine every thing expands and streching the head bolts or studs, and compressing the head gasket, when engine cools every thing goes back like it was before the warming of engine, making every thing a little looser, so every thing needs to be tightend up so that why you retorque after running engine, to remove all play in bolts and gaskets

[Mike V. Florida]

You will find those that swear warm and those that swear cold. There is no one correct answer. (like which oil to use)

[CarlG]

Some just swear

[johnsor]

As Larry B. recommends, when retorqueing after cool down, back off nut 1/8 turn then retorque to spec.

[Dave in MN]

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I think the thread you are referring to was in regard to a Snyder Premium headgasket. The manufacturers instructions suggest cold. The following is from their instructions. But let me warn you...you better torque more often shortly after installing...

CAUTION!

BEFORE DRIVING VEHICLE

1. Warm engine up slowly for 15-20 minutes.
2. Let engine cool overnight, or until stone cold (6 hours minimum).
3. Retorque cylinder head to 55 foot pounds using correct torqueing sequence.

4. Repeat after 500 miles.

[Purdy Swoft]

After installation of the head with 55 ft. lbs. torque applied in sequence, I let the eng idle for 20 minutes, shut it down and retorque hot in sequence. The reason for this is because you lose so much torque after the first start up, you don't want to run the risk of water entering the combustion chambers. All other retorqueings are done cold. If you use grade 5 studs like I now use, it will usually require at least two or three more retorqueings until it holds 55 ft. lbs.

[MrTube]

Why does it loosen up? Is it because all of the studs stretch slightly as it warms up but don't return as it cools? If so, wouldn't doing it multiple times cool end up breaking the studs eventually?

I'm asking because I'm curious.

[Dave in MN]

Originally Posted by MrTube

Why does it loosen up? Is it because all of the studs stretch slightly as it warms up but don't return as it cools? If so, wouldn't doing it multiple times cool end up breaking the studs eventually?

I'm asking because I'm curious.

It is because the thickness of the head gasket is decreasing as it passes through the heat cycles...guys that try to treat the Snyder's Premium Silicone head gaskets like copper gaskets (less times torquing) have the failures. The silicone gaskets require a few extra sequences of torquing to seat the fire rings before you run the engine hard. I assume it is because the silicone beads that surround the wet holes "squish" ...spread out when the head and block get hot and lessen the torque on the bolts. The waterjacket openings may be sealed but the fire ring may not be clamped enough to retain the combustion forces if pushed hard. I dyno test my engines and need to torque the silicone head gasket 4 times before I can load them heavily.
Good Day!

[Ron/IA]

I thank everyone for their replies. I seems that re-torqueing when cold is the logical way. Also, I am reading you re-torque as many times as required to a point where torque is no longer needed (ie. head nuts just don't turn when torqued to spec). Also, to not heavily load the engine till you get to that torque point.

As is the case with most threads (I didn't say all), a solution has been made.

Ron/IA

[sconnors]

Just had my engine done by Al at the godevil garage and he said to torque them and I quote "stone cold" so that's good enough for me!

[BILL WILLIAMSON]

Used the modern gasket on Minerva, after a 30 minute run, only 1 nut took some tightening. Next morning when COLD, all the nuts took some tightening, Except for the one that took some tightening when it was HOT!
Y'all do what you want to, but I DON'T loosen them when re-torqueing! Bill W.
(I am the proud new owner of this Sunnen torque wrench!! SANTA CLAWS restored it, like NEW fur me & it's TOTALLY ACCURATE!)

[Mitch//pa]

dad you can take your own picture now lol

[Ron/IA]

I am glad there is evidence that cold re-torqueing does produce results.

Bill - you stated you do not to back off nuts when re-torqueing. Do you have a reason? There are "experts" in the field that say do so.

Ron/IA

[PC/SR]

FWIW an old article in Hot Rod magazine says to retorque aluminum head hot, cast iron heads cold. No explanation why. Personally, I torque a few times over a period of hours or overnight on installation, retorque hot after 20 minutes of initial running, then some more when cold and hot for the next few days. Hey, it only takes 10 minutes.

[BILL WILLIAMSON]

Originally Posted by Ron/IA

I am glad there is evidence that cold re-torqueing does produce results.

Bill - you stated you do not to back off nuts when re-torqueing. Do you have a reason? There are "experts" in the field that say do so.

Ron/IA

Well, Ron, I consider myself my own EXPURT from years of doing this crap.
Why loosen & let a part of the head "raise" up & "break" an area of "seal" & be back to where you were in the earlier part of the tightening process? Bill W.
(Establishing the "seal" is a "one shot" process!)

[Dave in MN]

Hey Bill I get what you are saying if you loosen them to much... but the amount most folks loosen them is just enough to break the static friction and then two dog hairs more...then without removing the socket from the nut...immediately back up to torque. When you hear that little "tick" as you are loosening them that is about all it takes. Follow the suggested nut sequence working from the center out.
Good Day Bill!

[Ron/IA]

Bill - What Dave said!

Ron/IA

[BILL WILLIAMSON]

Upon initial assembley, if the threads are smooth & clean & oiled lightly, there's NO need to break them loose to lessen so called static friction. If a nut moves at 55 # torque, it DID need tightening, if it didn't move at 55 # torque, then it DIDN'T need tightening. One of the MAIN reasons for torqueing is for UNIFORMITY.
Not trying to be a smart ass or argue the point, just trying to help some folks that may not know the whys & wherefores of torqueing. If some of you have different ways of doing it and it's worked well for you, JUST STICK WITH IT! Bill W. (I'm EASY, but not CHEAP!)

[Mike V. Florida]

Originally Posted by BILL WILLIAMSON

[B]if the threads are smooth & clean & oiled lightly,

Right! 80+ year old nuts and studs smooth and clean.

Every mechanic I have every spoken with say to loosen approx 1/8 turn and then tighten in one smooth move.