Tighening head bolts

R

Ron

New Member
My car has a build date of 2000 and I presume it has a 4G93 engine (because its written on an identification plate) but as yet I haven't spotted it on the engine. Haven't had it long. Some work to do.

I haven’t yet removed the head, but reading though the manual on refitting I became puzzled in regard to tightening the head bolts. The book refers to 4G13/4G15 engines and 4G92/93 engines.

In the specs under torque specifications listed separately are the following:

4G13/4G15
Cylinder head bolts 73Nm (in sequence)

4G92/93
Cylinder head bolts
Step1: 75Nm (in sequence)
Step2: Loosen fully in reverse order
Step3: 20Nm (in sequence)
Step4: Turn 90 degrees additional (in sequence)
Step5: Turn 90 degrees additional (in sequence)

The book describes refitting the head by noting the following:
1. Tighten the bolts in several stages following the proper sequence to the specified torque.
2. Assemble the engine, start the engine and run to normal operating temperature.
3. Shut off the engine and re-torque the head bolts, unless the gasket manufacturers states otherwise.

With the 4G13/4G15 you worked the bolts up to 73Nm, warmed up the engine, and with the torque wrench still set to 73 you go over the bolts again. That’s straightforward. The bolts might turn. They might not.

However, with the 4G92/93 you have really no idea of what the final tension of head bolts are torqued to. After an initial pull down to 75Nm you back them off fully. Then you nip them up to 20, plus a quarter turn (that could well double the initial 20Nm). Who knows! Then another quarter turn (that could well put the actual tension up to 90Nm or more). No idea!

If they were left at that, I could understand it. But the thing is, after you warm the engine, what procedure do you adopt, and what do you set the torque wrench to? There’s no way you’d want to back them off again on a hot engine. And if you try for 75Nm who’s to say that is high enough after all these quarter turns.
 
*zombie post but for other viewers reference

It is because the 4g93 head bolts are torque to yield, meaning they are only ment to be used once and not reused/ retightend otherwise they can break. Thus the manual will not tell you a procedure that involves reusing the the bolts at original torque setting. I'm guessing they give you basic tourqueing procedure and let you decide exact amount based on bolts you use? Or am I rong?

Weather they can actually be reused or not I am not sure.
 
I've got a cyl head that will be refitted to a 98 lancer 1.5 engine (4G15) soon. (See link below) Reading the torque sequences is kind of interesting and in some ways archaic, if not confusing and on par with the cyl head tightening sequences of my 1942 WLA air cooled motor cycle (military workshop manual) where it's all done by 'feel' literally in the field...and I do mean field!

NOTE:
Below is the head torque tightening sequence taken from Ron's initial post above.
The initial torque figure given in Nm for a 4G15 engine (1.5 litre) is 49Nm or 36 ft lb, if using Imperial torque loading specs.

I've got a Warren & Brown torque wrench bought in my youth that I'll be using for the task and to also find out what torque the 2 extra 90° wrench turns apply.

I note that the bolts are specified torque to yield (i.e., simply put...a stretch bolt) The head bolts are being replaced with new as the engine had a severe over heat cycle (daughters will do that!) but I'll be reusing the conrod bolts as that end faired well.

As far as the conrod bolts go though...I'll use the WSM two stage method once on one rod to gain an accurate torque reading...back off and retorque to that figure. I'll then simply re-torque the other conrod bolts to that figure.

As part of the process though, I'll fit one complete rod with piston but minus the rings, then turn the crankshaft over several times to see if any bind is evident. Over torquing rod bolts is a bigger issue which can readily lead to seizure on a journal.

I'll be looking for a torque loading somewhere in the 30 - 35 lb ft range (41 - 48 Nm) which is pretty standard for a conrod torque across a broad range of engines (V8, 4 & 6 cyl) using similar conrod design.

All the threads/will be oiled (using engine oil) before torquing. Although torque to yield bolts, I'll use loctite threadlocker 272 as added insurance on the conrod nuts.

4G15 (1.5 litre)
Cylinder head bolts 49Nm initially (in sequence)

* It seems...unless I've missed something...that the initial torque sequence is done in one go. This is generally not good practice and I'll do it on 2 stages to minimize distortion on a freshly surfaced alloy head.

(From Ron's initial post...I've changed the Nm number to 49 to suit the 1.5 litre engine)
4G15
Cylinder head bolts
Step1: 49Nm (in sequence)
Step2: Loosen fully in reverse order
Step3: 20Nm (in sequence)
Step4: Turn 90 degrees additional (in sequence)
Step5: Turn 90 degrees additional (in sequence)

The book describes refitting the head by noting the following:
1. Tighten the bolts in several stages following the proper sequence to the specified torque.
2. Assemble the engine, start the engine and run to normal operating temperature.
3. Shut off the engine and re-torque the head bolts, unless the gasket manufacturers states otherwise.

With the 4G13/4G15 you worked the bolts up to 73Nm, warmed up the engine, and with the torque wrench still set to 73 you go over the bolts again. That’s straightforward. The bolts might turn. They might not.

http://www.auslancer.com/index.php?threads/overheated-lancer.10235/#post-233886

Note: In the last paragraph the torque loading for a 4G15 engine head bolt should be 49Nm not 73Nm.

This info will be followed up and cross posted to the above link.
 
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