Head gasket instructions

[CAMB01]

You'll see what kind of surface it already has, so IF it needs to be made flat again or to refinish a spot/s where the combustion gas has eroded the metal, just cut it the minimum with that same surface finish.
Forget the crack/pressure testing. It hasn't SERIOUSLY overheated & melted plug wires, so if the gasket looks bad that's what it is. It's only SOP to run up a bill$$.
Hardness testing seems to be for some sort of Australian old wives tale, forget that too.
The head bolts are re-usable, they are not TTY one use bolts but the do happen use the torque-angle method for tightening. I would re-torque the head after a dozen or more heat cycles and then you cannot use the factory torque-angle method on the already compressed gasket.

What are you smoking over in Florida?

[RS13]

Forget the crack/pressure testing. It hasn't SERIOUSLY overheated & melted plug wires, so if the gasket looks bad that's what it is. It's only SOP to run up a bill$$.
Hardness testing seems to be for some sort of Australian old wives tale, forget that too.

Wut? Got dodgy backyard mechanic much? If you're going to do a job, especially on your own car that you're using regularly, that money spent getting it tested might save you having to rip it all apart again in a weeks' time.

Hardness testing is as important as crack testing! If you've overheated your engine badly, as aluminium can anneal itself at as low as 300 degrees celsius (depending on the alloying agent), you may well have softened the head, so if the option of getting it checked is there you'd be silly not to.

[MAGN1T]

That hardness testing is a new one.
Best thing is to pull it to bits & take a pic. That way you might have an idea of what needs doing. An engine reconditioner will always skim the head. If it still leaks when it's back together it'll be because you didn't skim the block.

Steve

[CAMB01]

Steve hardness testing has been around for a long time, i started motor machining back in 2003 and had been around for a while since then.

[pc]

The head bolts are re-usable, they are not TTY one use bolts but the do happen use the torque-angle method for tightening. I would re-torque the head after a dozen or more heat cycles and then you cannot use the factory torque-angle method on the already compressed gasket.

I'm fairly sure that a torque-angle method means that the bolts are torque-to-yeild.

[frost]

Steve hardness testing has been around for a long time, i started motor machining back in 2003 and had been around for a while since then.

hardness testing is a must for diesel engines, not really petrol correct?

[MAGN1T]

I think it's just another item to add to the bullshit list when it comes to dealing with the motor trade in NZ.

Well if you take into consideration that the combustion chamber gets to EGT temp but the water jaket doesnt then what are you going to test for hardness ?

There's obiously a gradient in temp from the combustion chamber to the water jacket. So any theory is BS.

Steve

[allencr]

I'd happily learn something & apologize to all if anyone can find anything anywhere, some reputable tech about testing aluminum automotive heads for hardness, except the BS in downunder forums and in head rebuilding sites that use very high heat to decarbonize & clean them.
Also, ..... wouldn't know a TTY bolt if it was up his ....

[CAMB01]

Steve maybe you should go ask your son about some education on hardness testing cylinder heads.

[touge_ae101]

had to replace the head on my old rb20det as the headgasket was replaced by a backyard mechanic and was slammed back together and starting leaking again. found out the head ended up warping after a while. got the hardness test done and was way out of spec so had to get another one. 500bux later...

it makes sense that the head itself needs to be structurally strong enough to withhold the pressures of the combustion inside the engine, and hardness is a way of testing its mechanical properties to ensure it doesn't warp out of its desired shape.

[frost]

As it turns out most automotive cylinder heads are hardened to what is known as a T6 hardness. This hardening process is done shortly after the part is cast and serves to relieve casting stresses and to create a more uniform metallurgical structure. The T6 hardening process involves heating the casting to 1000F for about 6 hours and then quenching the part in water for a few seconds. Next the part is 'aged' in an oven at about 320F for around 5 hours and then allowed to cool to ambient temperature. The result is a part that has a Rockwell hardness on the 'B' scale of around 84-88 and a nice dense and uniform metallurgical structure.
# The solution - keep it cool!

Sounds simple but that's the truth. Again the only reasonable method to achieve cooler cylinder head temperatures is to use some form of water cooling. Water cooling solves all of the problems described above. A water cooled engine's cylinder head is usually kept to around 200F, well below the critical temperature of 320F above which a T6 heat treatment is destroyed. Furthermore a T6 heat treated cylinder head will retain pressed in valve seats substantially better reducing the possibility of one coming loose and the resulting catastrophic results. A water cooled cylinder head also has far less temperature differential across the cylinder head during operation further reducing the thermal stress.

from http://www.liquidcooledairpower.com/lc-topendheat.shtml

and from other reading,
it seems after repeated skimming of the head surface, it takes away from the hardened outer layers, thus more susceptible to bowing, cracking and loss of surface hardness,

[MAGN1T]

Repeated skimming makes it too thin and too weak. The roof of the combustion chamber lifts under pressure and unseals the gasket. So if you were serious you'd do a "deflection " test. It's been well documented in books ever since Fords first OHV V8 50 plus years ago. That's with cast iron heads, modern 4V aluminium heads being the same but better design due to the sparkplug in the middle giving more support.
Nobody seems to know how to read books these days.

Of course if you've cooked it several times then the head will be the least of your worries because the rings might have overheated, lost tension and you'll find it smokes badly when back together.

Steve

[Adamal]

Take a look inside the oil cap for any sort of coffee coloured gunk. Also check the radiator coolant to see if theres anything similar to that in there.

It'll help to see if the water and oil are getting mixed up

[Mr Revhead]

Stuck in a rut old men.
Old ways are not always bad ways, but they are also not always good ways.

[iOnic]

Is it at all possible that things have changed in the past half a century? Surely not...

[RS13]

Callum, due to the amount of incorrect information in this thread, I would disregard pretty much everything, take the head off, ring your local cylinder head specialists and see what they offer, and get your prices as well.

[pc]

The head bolts are re-usable, they are not TTY one use bolts but the do happen use the torque-angle method for tightening. I would re-torque the head after a dozen or more heat cycles and then you cannot use the factory torque-angle method on the already compressed gasket.

I'm fairly sure that a torque-angle method means that the bolts are torque-to-yeild.

Oops, other way round.
Here's an article that explains it reasonably well. http://www.engineproblem.com.au/torque.htm

[loudstealthGT-Four]

Callum, due to the amount of incorrect information in this thread, I would disregard pretty much everything, take the head off, ring your local cylinder head specialists and see what they offer, and get your prices as well.

best advice on this entire thread

[DFECTED]

I'm fairly sure that a torque-angle method means that the bolts are torque-to-yeild.

Yip, you arent ment to but I have reused them on many motors

Steve maybe you should go ask your son about some education on hardness testing cylinder heads.

LOL. I have seen many alloy heads go soft and a few continue to blow headgaskets because they are soft. They go soft around the exhaust valves and between the cylinders on the surface. On the worst case scenarios after a head has been skimmed you can see the softer parts are a cloudy colour when the rest is shiney.

Some manufacturers are more prone to going soft as they use a cheaper alloy material

Repeated skimming makes it too thin and too weak. The roof of the combustion chamber lifts under pressure and unseals the gasket. So if you were serious you'd do a "deflection " test. It's been well documented in books ever since Fords first OHV V8 50 plus years ago. That's with cast iron heads, modern 4V aluminium heads being the same but better design due to the sparkplug in the middle giving more support.
Nobody seems to know how to read books these days.


Steve

We skim more than 2mm off faclon 6cyl standard stocks to bring them up to 10:1 compression, these are 2 valves per cylinder and the sparkplug in the side, they run flat out for seasons with no issues. A typical head skim will remove around .1mm

Take a look inside the oil cap for any sort of coffee coloured gunk. Also check the radiator coolant to see if theres anything similar to that in there.

It'll help to see if the water and oil are getting mixed up

Milkyness under the oil filler cap doesnt really mean much as condensation builds over night, whats more important is if its on the dipstick or in the radiator

[Flannelman]

How to remove a head - 20V ...

1. Drain radiator, remove heater hoses and radiator hoses
2. Remove timing belt
3. Remove plenum
4. Remove wiring to oil pressure, A/C, VVT solenoid, injectors, Knock sensor, Idle control, distributor, temp sensors, and earth off the head
5. Unbolt supports from block to under throttle bodies
6. Unbolt coolant tube off back of head. Release hose off back of water pump and twist tube away from head
7. Remove rocker cover and intake camshaft. (Need to be removed to get to the head bolts)
8. Unbolt head

Did I miss anything?