Head bolt retorque - warm or cold?

[VTCDN]

Are we still talking about 2Fs here?

""Head bolt retorque - warm or cold?""
Was the question of this thread !!

I was just bring up Cold and the method of some manufacturers.

Hot is an impossible task to do a re-torque really , By the time your at the last bolts the temp has changed way to much, Plus I'm almost sure a bolt would of been pulled "necked"..

Better question would be !!! is How many who replace head gaskets because of overheating ever replace head bolts , Or on the second head gasket replacement because of leaking and overheating again EVER measure the length's of the bolts??

Bolts stretch as they get overheated under torque and NO longer can hold there tightness under stress(torque load).

Do what YOU want , But for some Manufacturing repair shops there is a re-torque service that you must comeback for to make sure the factory warranty will stay intact .Not all work , But say a replacement exhaust manifold gaskets needed it would get a re-torque after one heat cycle in the shop and another booked in later , And done cold.
3rd job this AM.




VT

 

[FJ40Jim]

Some gaskets require a retorque. Most new gaskets do not require a retorque. I recommend a retorque of both head & manifold gaskets to be safe.

From the F engine manual, page 2-5:
"General engine inspection"
1. Warm up engine to operating temperature (75-85C*).

2. Tighten the cylinder head bolts, manifold retaining nuts, and the valve rocker shaft support retaining nuts and bolts to specified torque.

3. adjust valves...
/endquote

Head bolts do not stretch because of overheating. If the head bolt is hot enough to reach the yield temperature of HSS, the entire engine is probably on fire.

Most new engine head bolts do stretch by design and should be replaced whenever removed.

Older 2F and F headbolts do not stretch by design and never need replacing, unless damaged. Note that new headbolts are only available from Toyota in the updated semi-stretch style, so if replacing headbolts on an early 2F or F, all bolts should be changed to the new style.

If the shop that does your machine work is recommending retorqueing 2F headbolts cold, then I recommend finding a more competent shop that can RTFM. If it is necessary to deal with a shop that recommends this, then ask them to note that in writing, so that any warranty issues that may come up can be dealt with on the basis of their recommendations that directly contradict the FSM procedure.

 

[Benjaman]

Some gaskets require a retorque. Most new gaskets do not require a retorque. I recommend a retorque of both head & manifold gaskets to be safe.

From the F engine manual, page 2-5:
"General engine inspection"
1. Warm up engine to operating temperature (75-85C*).

2. Tighten the cylinder head bolts, manifold retaining nuts, and the valve rocker shaft support retaining nuts and bolts to specified torque.

3. adjust valves...
/endquote

Head bolts do not stretch because of overheating. If the head bolt is hot enough to reach the yield temperature of HSS, the entire engine is probably on fire.

Most new engine head bolts do stretch by design and should be replaced whenever removed.

Older 2F and F headbolts do not stretch by design and never need replacing, unless damaged. Note that new headbolts are only available from Toyota in the updated semi-stretch style, so if replacing headbolts on an early 2F or F, all bolts should be changed to the new style.

If the shop that does your machine work is recommending retorqueing 2F headbolts cold, then I recommend finding a more competent shop that can RTFM. If it is necessary to deal with a shop that recommends this, then ask them to note that in writing, so that any warranty issues that may come up can be dealt with on the basis of their recommendations that directly contradict the FSM procedure.

Books can be wrong. I know at the factory that the heads are done cold.

I'll stick with cold, as it has not failed me yet. Did my first in 78, been doing them cold ever since. Machine shops have only confirmed it for me.

 

[Pighead]

Books CAN be wrong, agreed. I no longer adjust tappets to the book's gap, nor time by the book. We've had very lively discussions about the correct birf lube, book vs. just about everything else. But the book, and it's essential truths, has been around for a long time, and I have to trust that Toyota would have corrected any glaring omissions or errors by now. Sure, the heads were torqued cold at the factory. I torque mine cold on the engine stand but re-torque after the 30 minute run-in. Did the factory re-torque while warm? I do not know.
I'll stick with warm, as it has not failed me yet. I did my first in '87, been doing them warm ever since. The above posts only confirm it for me.

 

[FJ40Jim]

The reason for adjusting tork at operating temp is because a specific gasket crush load is desired under operating conditions.

I'll stop now. The information has been presented, do with it what you please.

 

[4wdx4]

I was speaking in general terms, as in all things being equal, a mechanic is (for the most part) someone that works on cars, and nothing in the way of training is mandatory. A Machinist will often require in excess of 3 years training.
A good machinist could build an engine from scratch, as a mechanic could only assemble the engine. I should know, as I'm a mechanic that works hand in hand with machinist at a local refinery.

As a former machinist and A current mechanic (15yrs) I always go by what the factory recommends. They designed it and produced it. They should know what they are talking about. I have built many engines and cylinder head jobs but not on cruiser so I would still go by the factory recommendations.

 

[cwwfj60]

this is good to know since I plan on a rebuild soon, wouldn't have ever thought to check on retorque.

 

[TobyB]

I actually have something constuctive to add to a rather... amusing... thread:

Head gaskets come with an instruction sheet. The sheet's written for the gasket you bought.
It'll tell you what to do. And some gaskets want significantly different treatment than others.

The gasket's developed to work with your particular engine, and the makers have a vested interest in it sealing.

So I tend to do what the instruction sheet says to do.... and it works.

As to the head bolts, yeah, measuring and inspecting them's not a bad idea, but with the exception of
torque- to- yield bolts used in modern aluminum head motors, head bolts don't change their properties
over time- yes, they stretch and shrink, but they do so elastically. So it's not particularly necessary to
replace them as a matter of course. It doesn't do any harm, but it's of limited benefit compared to something
necessary, like replacing gaskets...

fwiw,

t

 

[Hugh Heifer]

Older 2F and F headbolts do not stretch by design and never need replacing, unless damaged. Note that new headbolts are only available from Toyota in the updated semi-stretch style, so if replacing headbolts on an early 2F or F, all bolts should be changed to the new style..

Hey Jim, for the sake of tech, what year (if any since you say 'older' headbolts) did 2f bolts change making replacement a necessity? Or do you mean any of the original f or 2f bolts. How can one tell if they are the early one ones?

Also, do you recommend chasing the threads in the block before reinstallation of head bolts?

 

[FJ40Jim]

The headbolt change is undocumented. It occurs when the 2.5F comes out about 1/85. No F/2F/3F bolts are a must replace type.

Pictures show heavier 75-84 bolt and skinny 85-92 headbolt w/ indented head. The later bolt has a 1mm shallower head and 2mm longer working length.

Yes, all HB should be wirewheeled to remove carbon and all boltholes threadchased to remove carbon. Best to roll block upside down and blast holes w/ blowgun before beginning block assembly.

 

[Hugh Heifer]

Thanks for the quick response Jim

 

[TobyB]

Oh, poo, here I go with even more questions-

so I've been taught and told (mechanic, machinist, Carroll Smith, and BMW factory manuals)
that non TTY head bolts should be broken loose to be retorqued.
As in, back it off just enough to get the threads to turn freely, then re- click it.

Jim, does that reflect what you do?
Or do you just give a tug on 'em to make sure they're not statically loose?

thanks,

t

 

[FJ40Jim]

so I've been taught and told (mechanic, machinist, Carroll Smith, and BMW factory manuals)
that non TTY head bolts should be broken loose to be retorqued.
As in, back it off just enough to get the threads to turn freely, then re- click it.

This is a good procedure.

Or do you just give a tug on 'em to make sure they're not statically loose?

This is what I do.

 

[LAMBCRUSHER]

This is a good procedure.



This is what I do.

 

[Godwin]

2F at the root of this thread has many, many more miles on it and no head/head gasket issues.

 

[TobyB]

This is what I do.

Thank you, Jim!

t

 

[grant5127]

Never needs retorquing...

 

[OGBeno]

The headbolt change is undocumented. It occurs when the 2.5F comes out about 1/85. No F/2F/3F bolts are a must replace type.

Pictures show heavier 75-84 bolt and skinny 85-92 headbolt w/ indented head. The later bolt has a 1mm shallower head and 2mm longer working length.

Yes, all HB should be wirewheeled to remove carbon and all boltholes threadchased to remove carbon. Best to roll block upside down and blast holes w/ blowgun before beginning block assembly.

Very cool information here Jim. This is probably one of the first times I have seen an ostensive difference in the parts with no part number change.

As you well know, any time there is a supplier change, part update, part revision, or engineering change, usually the part is updated to reflect this in some manner--usually in the last 5 digits of the part number (very recent example, 7x/8x front axle felt wiper packs: last 5 digits changed from 60031 to 60032 when they changed the metal ring from that brass looking color, close split in the ring, to a wider split in the ring and black painted metal. Also, the metal seems to have gotten chintzier. )

There is indeed no way to get that earlier bolt it seems. The current part number goes back to 1/1975 with the introduction of the 2F.

 

[augirthedude]

My 1986 Toyota Land Cruiser manitenance procedure manual does not even mention re- tightening of the head bolts during a valve adjustment. However I do re-torque the cyl. head bolts by just pulling on them with the Torque wrench, I do not loosen the bolts after installation. if that was the case the FSM would instruct you to. IMO.

 

[augirthedude]

I used to proof Subaru of America FSM 's during the 70's and 80's translating Japanese English to American English . In the original edit from Japan there was quite a bit of phrasing that really did not make sense. SOA provided us with a car and the manuals and we went through every procedure in the manual taking notes and correcting the ambiguities in the manuals. The FSM's are a good reference , better than say a Haynes Manual but sometimes the manuals do not spellout every move you should make during a procedure. I have some old Harleys (60'S) and have FSM'S for these vehicles. These older manuals assumed that the tech knew what he was doing and were fairly vague. and refered to common shop practices . Happy motoring !