Quote:
Originally Posted by rusted and busted
The long bolts go under the valve cover and the short are by the exhaust manifold (if you have a '99 the short ones are a stud with a nut. As far as I know all 2.2's have the torque limit bolts so don't worry about the bolt specs because you have to buy new hardware from a parts store.
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Thanks for this info.
So according to this, one only has to buy 5 replacement bolts,
since the front ones are not bolts at all, but studs.
If this is so, it seems doubtful that the front studs/nuts are actually
"torque-limit" bolts. They would probably be ordinary steel.
Here is something I found on a Q&A site:
Quote:
very vehicle uses head bolts to fasten the cylinder heads to the head gasket of its engine. In order for head bolts to work correctly, they must be torqued in a specific sequence and to their required foot-pound measurement. If head bolts are not torqued properly, they can potentially cause crucial damage within the engine. Basic Specifications
- Every engine has its own, distinct specifications. The cylinder pressure that exists in the engine directly correlates to the amount of torque that's needed to hold the cylinder heads in constant contact with the engine block. The amount of torque a cylinder bolt requires for a head bolt is determined by dividing the total number of bolts by the cylinder pressure that's produced in the engine's combustion chambers. For instance, for an engine that produces 2,200 pounds of pressure with four head bolts in the engine, each bolt must be torqued at 550 foot-pounds.
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If the above explanation is accurate, we can not only understand the principle behind the bolt-tightening,
but also calculate how to double-check the figures,
and even understand that one can and should "over-tighten"
in principle, to safely counter opposing forces.
The main idea then, is:
(1) Tighten them enough to counter the explosive pressure against the head.
(2) Tighten them evenly, to prevent distortion and leaks.
From this understanding, we can see that one can probably "over-tighten" a smidgen without harm (specs for bolts, threads, and casting should have safety margins),
while "under-tightening" would be disastrous,
and uneven tightening would be just as bad.
If it is indeed possible for some bolts (or nuts) to loosen from vibrations etc., then evenness of tightening (load spread) has already failed, and the motor is simply waiting for a catastrophic gasket-failure.
So, it seems advisable on this count, to tighten all four front nuts/studs to 43 ft/lbs, plus one quarter-turn at least, as per original specs. Then at least one side of the head has its torque evenly distributed and should not become warped.
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On another Q&A board, I found this post:
Quote:
While removing the intake and exhaust manifolds, the studs came out.:-0
I think I have specs on how many foot pounds to tighten the nuts that
go on those studs (holding those manifolds in place).
But when I install the studs into my new heads, how tight should I tighten the studs themselves?
I figure they're probably listed in inch-pounds so
should I just kinda tighten them gently, or does the torque matter on those studs?
thanks
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This user asks a good question. If studs do tend to unscrew (because of siezed nuts),
how should they be re-installed?
To get the frozen nut off, one should have other nuts handy,
so you can use two of them (and maybe a plate of sheet-metal)
as a way to grip the stud-shaft without damaging the threads.
This seems like the best practice.
Once the old nut is off (using wax, heat, or penetrating oil etc.),
you have to re-install the stud/shaft.
There should be no "torque-value" per se, as this writer thinks,
because the "torque" is set between the stud and the nut. It doesn't belong to either piece alone.
What matters is that the stud/shaft be deep enough into the cast-iron block (or aluminium head)
so that the threads can't pull out or be damaged when the nut is tightened.
A good look at the original position of the nut should indicate how far the stud must be threaded into block.
However, one should double-check the remaining height against another properly seated stud.
The thread should be oiled and/or probably sealed with some special gunk,
in case the threaded hole is all the way through.
I read about this once in another thread on doing cylinder-heads.
I'll try to find that reference.
Once the shaft is re-threaded into position
(try using the extra two lock-nuts I described above, to screw it in),
and the gasket and head are restored on the block,
you can worry about 'torque'.
I would guess that these studs would be ordinary steel,
since they are not usually replaced, but are part of the block.
Only the inside-bolts are easily removable,
and would be expected to be the special softer type.
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On the other hand, if you have already had a leak,
This suggests serious damage to the gasket.
Simply tightening down the head might be a big mistake,
because if the gasket was worn, lost material, or got damaged,
or if some foreign deposits wedged into the crack (dried soot, coolant-residue),
then maybe putting the 'right torque' on all nuts and bolts will actually bend the head around the deposit or the missing pieces, twisting its shape.
One small question remains as to your own vehicle (see other thread):
What if one of the cylinders has a lower compression because there is still an internal problem (say caused by above)?
This would suggest that its only a matter of time before a small hole gets bigger, and you are back where you were again,
only this time with a bent head (from tightening without replacing gasket).
Just my thoughts...