Newly skimmed and rebuilt head and block
New Payten gasket from SNG
Engine rebuilt, head torqued and checked at least 4 times 54 ft lbs
We ran the engine a few times for 10 mins or so out of the car. Third time we saw water weeping from head in particular (front) water pump end sides. Checked torque again and found most head nuts about 45 ft lbs. tightened back to 54 (and have always done in correct order)
Ran again and had water leak again.
Damn
Pulled head and found definitely leak but not into cylinders but out to sides of block but in particular water seemed to be creeping up the four head bolts that are longer for lifting eyes.
These are new head studs again from SNG
First thought is head not properly skimmed and intending to get checked but wondered if anyone had any other thoughts. I am wondering if the longer studs and lifting eyes have maybe meant not properly torqued or something.
Thanks all for any hints.
Glad I built a frame and started out of car.
First though that comes to mind is either the head or the block surfaces are not dead-on flat. If possible, return the head to the shop so it can be rechecked for flatness and warping. Also, did they do a dye penetrate Non-Destructive Exam to check for cracks in the head? Did they do that? Take the block too! That’s the only cure. Sprays and the like for head gaskets won’t help in your situation IMHO. Those two mating surfaces have to be dead-flat.
Something isn’t correct if the torque reduced that quickly. As has been advised start with a flatness test. How did you install the studs?
Is the payment gasket a composite one?
Just thought, please make sure the the head nuts are not bottoming out before they clamp the head. It’s easy not to put the correct washers and brackets in place and thus have a longer than required thread section.
The head nuts should be easy to start by hand and the thread should be lubed (oiled) to s sure correct torque is set.
I’m no expert - our experience was similar - machined and reassembled with new studs and composite gasket - leaked like a bast**d - head gasket replaced with metal - no probs.
Studs installed into block first and screwed down to head a limit of thread but not torqued at that point. Head on and had new chrome kit from SNG and used the d washers and standard in correct places.
Didn’t oil threads thought but hand screwed on ok. Basically new everything.
Not sure about payten gasket but again was new in kit from SNG. I am going to get a Cometic one for the next time though.
Real pain as didn’t skimp on parts and got recommended engine shop by a Jag expert.
It had been running fine for first few attempts so didn’t leak originally but then left for probably two months on stand whilst worked on car. About to throw into car and thought would give one last 20 min run and that’s when first leak happened and found torque had backed off.
Only change I made really was getting longer studs for lifting eyes and eyes from eBay.
Going to get head checked again and speak to shop to see what they say. Will update and thanks for help.
I am not sure my english is good enough for this but I am going to give it a try.
I had quite the same problem, for me, the leak was via one of the rear stud. It was with a composite gasket, I had oiled the thread of the studs, the base of the nuts and the washers. But I had noticed during the last tightening sequence that the nuts didn’t rotate smoothly, but were jerking (is that english?).
When I noticed the leak, I decided to try a complete new tightening sequence, but this time, I applied a bit of high pressure grease on the bottom of the nuts and washer (NOT on the threads). And this time, everything went fine and no more leak.
So I believed that the problem in the first place was uneven and unsufficiently torqued nuts.
I spoke to the engine builder today and also got head checked. Head is fine and true but advice from engine guy was no faith in Payten gaskets anymore but whe he did use them but always gave them a mist spray of Hylomar. He also advised putting head nuts on dry was probably my isssue. Realistically not enough torque on them.
As J-Christoph with his excellent English (don’t worry J-C its great) they recommend molybidium (spelling??) grease on thread of top part of stud, top of d washer and base of dome nut but as Phil says make sure the thread doesn’t bottom (or top out) inside dome nut.
They also have used and recommend the Cometic gasket but even though they say put in dry they still put a mist of hylomar on it.
Also said they often over Torque by 5-10 ft lbs as they can take it.
Will get Cometic gasket, try again and grease nuts as above and update in a week or so.
Hope this helps some, learn by mistake I say
ps. Engine builder is highly recommended and old school here in AU. Been building and maintaining race engines for classic racers for many years so have much faith in them. Proper old school engineers.
Always run each nut down by hand to contact the head without a washer to check that you will have a clear full length of thread without any binding. The reason for ensuring there is ample thread length is because not only is the head pulled down a bit, also the stud is stretched slightly. I had one binding head nut once and only detected it by ‘feel’ - the tightening action felt different as the threads were gradually binding, even though the washer was gripped. The deception was found after running the nut down and noting that it contacted the washer, but when redoing it without the washer, the nut didn’t go down any further.
(As an aside, big end bolts are stretched slightly on full torque and should not be reused as a subsequent tensioning starts the fatigue process. This is usually the reason why a bolt breaks - it is subjected to cyclic tension loads due to the intake suction action pulling on it at several thousand times a minute.)
You may have to run a bottoming tap down to get thorough thread overlap and to eliminate any thread-to-thread interference. If there is room to turn a die nut, the threads on the studs should be dressed to.
Whenever you have the head off, make it a habit to dress the head studs as it is so much easier. (Remembering is the problem which I can vouch for.) Any threads subjected to high torque can suffer minute deformation of the threads which is why you may find one nut turning freely on one stud but not another.
Any ‘drag’ on the threads or contact surfaces reduces the actual torque for tensioning which is why good lubrication is essential to cut down frictional resistance. You can easily lose 10ft-lbs or more but more importantly, each stud will have a different nette torque despite the tension wrench clicking equally.
Just and update to this. Thanks all for the advice and seems us not lubricating the threads, dome nuts and d washers was the trick.
Also invested in some ARP head studs rather than ones from SNG and had a much better experience in torquing and hardly backed off at all after two weeks of checking.
