Hey Guys been looking at this topic for a while now and I just wanted to clear something up ACL hasnt gone broke nor are they in liquidation the are still up and running and doing fine if you have any issue with thiere gaskets give them a call they were great when I had an issue with mine and as it turned out it was an issue with my head not the gasket at all

Jmac, The thought had crossed my mind to have stud kit installed.

You're right about the need to back off the bolts before retensioning. The torque needed to get them moving will exceed the torque needed to keep them moving and thus give potentially a false correct reading.

When I checked them I simply put the torque wrench on to see how tight they were and they moved as described ,no backing off first.

I doubt if there would be much oil getting past the threads on the oil feed head bolt to cause an hydraulic lock.The point is well made though.If you removed and then reinstalled the bolt then I agree that it would become an issue then as any oil around the bolt will go to the bottom of the stud hole.

Fandatstik, Interesting you should mention that. I am aware of that problem however have no experience of that with the the Dato engine. I wonder what temps would be needed to cause that on a Dato head? The temperature recorded is viewed by others as not as bad as it sounds.

If the head has softened I query if it can be re-heat treated or is it then just a fancy looking block of silver swiss cheese ?

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Hopefully the head hasn't gone soft/annealed (due to overheating) and caused this..

You're not alone on that one. What I'd maybe suggest is not doing them too many times. I used to do it 3 times, 4 max.

There's a bit of difference of opinion (and I honestly don't have anything I could put forward to favour one over the other) as to 'how' to retension them. This is a general - 'not specifically datto a series' comment mind you

Some people raise issuesthat if you loosen and re-tension the bolts (by just cracking them loose, one at a time, then retensioning, then moving to the next, loosening and re-tensioning, in the same order you'd tension them first time around) - that oil or other fluid could get under the bottom of the bolt and hyraulically 'lock' and stop the bolt going tighter, but it'll register on the torque wrench as being tight. SO they just go one by one, don't loosen any bolts, and just re-tension.

THe 'other' side raises the issue that the bolts can slightly 'seize' and need to be 'cracked' then re-tensioned, or that stickiness will otherwise just make the torque wrench read a high value, but the actual clamping force isn't as high as it could be.

Both have some relevance I guess. For whatever it's worth, I've done the 'loosen one, then re-tension' then move to the next one etc method on practically all motors.

I tend to run studs on anything that has to be re-tensioned a lot. That way the threads in the block won't wear out, they are only pulled once in a blue moon, if changing the head gasket altogether. SO that saves the threads in the block. It also means that you are only loosening the nuts at the top, not the stud, so you have no worries at all with the 'crack one loose, then retension' method. It also was a bit of a bonus on things like holden red motors, as they have bolts going into the water jackets, so you need to run sealer (instead of anti-seize lube) on the threads to prevent seepage past the threads - which is then a real pain when you have to re-tension them (and arguably the sealer also leads to slightly less consistent torque wrench readings for the same clamping force. But with nuts at the top, you can seal the threads in the block, and use anti-seize on the top threads/nuts.

For a streeter i wouldn't bother too much with studs, but they have a decent advantage with more competition oriented stuff.

Last night we checked the tension on the head bolts and that was quite surprising. All of them torqued down quite a lot. They all went down around 45-60 degrees to reach the manufactures spec of 45ft lb which is what I originally set them at when the motor was assembled. So much for monotorque!

We are going to pull the head off and fit a new gasket. We will also be checking the tension of the head bolts after every meeting from now on.

I have to confess that the idea of a single tensioning of the head bolts after fitting a cylinder head is something I have never been comfortable with generally. Even moreso on a race engine.

Thanks to all who responded. All useful stuff.

Jmac, I like your thinking about the use of stock type gaskets and the "relief valve" approach to them.

The motor we are running now has flat tops and .060 over bore so we are getting quite good compression now compared with our old motor which only had those standard dished jobbies. That motor was more a set and forget type setup that was reliable meeting after meeting. Now it is making more power so everything is a bit more stressed including the head gasket.Once Ive checked the valve lash we'll decide what to do but I'm about 95% convinced at this stage we will pull the head to make sure all is well.

It might handle that temp fine without mechanically seizing or blowing the head gasket (as DD says, if the cap held pressure and it therefore didn't allow steam pocket formation etc).

BUT - and this is a 'maybe' - presumably it is running a comp ratio/timing/cam duration (even if the cam was stock, there's still a max timing/cr you could run, so I'm trying to cover all bases here by saying that) that is closer to the detonation/pre-ignition threshold than a lot of street driven motors might be.

That would then be, relatively speaking, more sensitive to a rise in coolant temp above whatever it was tuned/setup to run at in race trim.

If the gasket is blown bad enough to affect the idle massively, it is at least likely you'll see bubbling in the radiator at idle (or whatever revs you can keep it going at) with the cap off. Sometimes they can just blow between cylinders and that won't see any coolant loss/contamination. Same deal with water in oil and or oil in water.

It's probably worth the time to pull the head and get it checked out if the usual tests (as mentioned in this thread) show nothing up.

It totally depends on the type of racing and so forth, but on a couple of mates cars, they've deliberately run stock head gaskets instead of copper ones, on the theory that they are fine to cope with normal pressures/usages, and will only blow (acting like a fuse of some sort) with abnormal combustion - too hot, detonation, preignition etc. Sure it meant they were replacing the gaskets every few race meets (this was entry level speedway racing, so whilst the combinations were pretty tightly regulated and modest, the amount of punishment the engines had to take was still higher than moat people could likely ever put them through on the street)

225F is not bad. The engine can run at that temperature all day if the radiator has a 15psi cap. As long as the water didn't boil out, it should cause no harm.

212F thermostats are very common.

Test gasket- oil in water water in oil? Or do co2 test in rad coolant.

225 not that bad if short time only. Might have detonated or similar

I realise this is resurrecting and old thread however it is still a relevant topic today.

Has anyone had recent experience with the Monotorque head gaskets?

We are using one on our Junior Sedan and suspect a failure after only 3 meetings. We experienced some overheating due to mud on the radiator core and reached about 225 deg.F ('ken hot!)

Now, we can't get it to idle properly. Changed carbs and no difference so that is eliminated from the range of possibilities. No vacuum leaks. On raising the RPM it runs smooth.Still investigating at this stage and need to eliminate valve lash as a possible problem. I am now inclined to the view that the head gasket is the source of the problem.

Any suggestions or comments?