Re-Torque Head Bolts?

[minuteman62-64]

Appears a number of you do this as part of annual maintenance. Seems like a good idea, but I'm not sure exactly how to do it. I think I read somewhere that if I come by every year and just tighten them to the torque spec I'll be increasing the actual torque on the bolts each year.

So, what's the process? Loosen one at a time and re-torque to spec? Remove, one at a time and apply appropriate stuff (my repair manual specifies Loctite A), then re-install and torque? Or, loosen or pull all and re-install and torque? Preceding recognizing that the torqueing is to be done in a prescribed sequence.

Appreciate any input.

 

[gm280]

I kind of doubt that many folks re-torque the head bolts on their engines on a yearly bases. I've heard that after an engine rebuild it is a good idea after an initial start up and cool down, but I don't see many if any folks doing that as a yearly maintenance schedule. And if the bolts are at torque, which I'd imagine they would be, re-torqueing them would merely be going over them in the proper sequence and making sure they were at proper torque. I don't see removing the bolts and reinstalling them and torqueing... But that IS just my opinion...

 

[Frank Acampora]

Well, remember that the head bolts are never re-torqued after they leave the factory! There are engines out there 30-40 years old which have never had the head(s) removed and never had the bolts re-torqued. This is not a required annual maintenance item!

If you have not removed the head and installed a new head gasket, leave it alone. This is a case where many do-gooders on the 'net simply make more work for themselves! to paraphrase your statement: "Sounds good, so why not do it?"

However, if a new head gasket is installed, then it is good practice to re-torque the head bolts after running for about 1/2 to 1 hour. Exception: OMC engines with O-ring sealed heads do not require re-torqueing. Once re-torqued after heating, it need never be done again. The reason for re-torquing is that the head gasket compresses during the first run when heated to operating temperature, loosening the bolts a tiny bit. If re-using an old head gasket, it is already compressed so there is no need to re-torque it after the first run.

To re-torque a new head gasket, loosen each bolt in the loosening/tightening pattern and torque to specifications in three steps. this prevents the head from warping.

 

[minuteman62-64]

OK, if it ain't broke, don't fix it. Makes sense to me.

 

[Sea Rider]

Will not speak for all engine brands, Tohatsu, Nissan, Merc, Mariner Service Manuals recommends a head torque to specs with torque wrench inmediately after break in period from new, we're talking about engines that uses traditional head gaskets. But few re torque, dealer should do it if owner sends engine in for first maintenance.

One thing that have found is that if you re torque head gasket at 10 or 200 worked hours the head bolts won't move a bit, seems that factory first installs all powerhead gaskets, retorques them to specs, then paints the entire unit, so bolts have lots of paing over them which maintains them paint welded against power head.

In this pasrticular case should back each bolt so to break the paint seal and then procede to re torque each bolt to specs following torque sequence specified for each block. With use, time and heat head gaskets tend to cede and if slight loose will see thin salty white lines formations adjacent to gasket specially if engine is used on salt water.

Usually re torque all my engines at 150-200 meterd worked hours and a head gasket change every 500 worked hours no matter if engine still runs top, Take advantage to decarbon whole combustion chamber, including cleaning block, head, water passages and thermo spot on as when factory delivered, engine cools much better and disipates heat faster, but that's me...

Happy Boating

 

[Faztbullet]

I would reread your manual as I don't know of any that recommend Loctite on head bolts.....If motor is a salty/brackish water leave em along as you can open a bigger can of worms.

 

[bilge rat jim]

Leave them alone. As you said, "if it aint broke.............".

 

[minuteman62-64]

I would reread your manual as I don't know of any that recommend Loctite on head bolts.....If motor is a salty/brackish water leave em along as you can open a bigger can of worms.

Clear as day, says "Loctite A." If the "A" is, in fact, equivalent to today's "Red", makes no sense at all. BTW, it's '82 Mariner, 30 HP.

 

[racerone]

Sorry mates,---It is a very good practice to re-torque the head bolts on an annual basis.----Never loctite them either !!---The problem is that the head bolt is steel.--------The head is aluminum.--The aluminum expands more than the steel bolt with heat.---This puts more pressure on the gasket each time the motor heats up.--Eventually the torque on the bolt is lost as gasket has been squeezed more.-----So do a re-torque on them each year !!!!!

 

[Sea Rider]

It's not only a ceding gasket re torque over time issue, it's all about avoiding corrotion and rust on both crankcase and head mating alum surfaces and metal rings detereoration in middle head gasket, much worst if engine is used on salt waters. All combustion chambers must be spot on sealed to achieve 100% perfect combustion for engine to run top. When OB's starts to use cooling green stuff as in cars, will be another story..

Happy Boating

 

[dingbat]

....

 

[Sea Rider]

If you already have a cylinder head with seepage issues specially if running on salt water, a head re torque won't fix the prroblem, there's already salt deposits sitting betweeen gasket and mating surfaces. A new head gasket would be the way to go for a 100% perfect combustion chamber seal. Anyway, open your Owner?s Manual to check if manufacturer reccommends a head gasket re torque for that particular HP brand engine.

Happy Boating

 

[UncleWillie]

The Head Bolt torque spec is commonly the same number as the "Torque to Yield" number.
What you are doing is tightening the bolt to the point that it starts to stretch.
It is as tight as it is going to get. It is a half turn from breaking.
In essence, it is now an extremely strong spring holding the head in place.
Ever notice that most head bolts have have threads one the end and a long skinny body with a big head?
That long body is meant to stretch.
If the Head expands and contracts a few thousandths as the temperature changes, the bolt stretches and retracts to follow the movement.
If you repeatedly te-torque the bolts, they will eventually break. Now you will have a problem!
If you need to loosen them for maintenance on the head, the bolts should be replaced and not be reused.
They may look perfect to the eye but they have been strained and are now a few 0.010's longer.

If it "Ain't" Broke......

 

[bruceb58]

There are two types of head bolts. Normal head bolts are never torqued past the yield point. You could get away with re torquing those if you know that is what you have. Torque to yield bolts are torqued past their elastic point and you would never want to re-torque those. In fact, torque to yield bolts are generally only used once.

http://www.acl.co.nz/wp-content/uplo...-Headbolts.pdf