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MG MGB Technical - Cylinder head studs quality
|Can anyone recommend a source of decent quality cylinder head studs and nuts? I am wary of some of our mg spares suppliers who these days seem to be sometimes selling parts of dubious quality.|
Is it possible to replace the studs (one at a time) without removing the head?
I've removed the head a couple of times this year, and retorqued recently, but when doing this I noticed that the long studs (that also secure the rocker shaft brackets) needed between 1/4 and 1/2 a turn more to re-torque, and the shorter studs all needed less than 1/4 turn more. My first thought was maybe the studs are stretching. The car and engine have done a genuine 42k miles from new, and the recent head removal is the first time it's been removed or disturbed.
|Brian, the original studs are good, unless obviously damaged.|
The studs do stretch under torque, as do all bolts & studs, and the longer ones will stretch more. Don't worry!
Studs can be removed w/o the head off provided there is room to jam two nuts together. Studs should not be too tight into the block.
|As Art says, don't replace them unless absolutely necessary.|
|Go to the Octarine web site, Chris sells the good ones in his online shop|
|I installed a set of ARP head studs after a head gasket failure on a low mileage engine. Our original head studs are several decades old now and were never designed to go through the countless heating and cooling cycles that they have been exposed to. New studs, available today, are of dubious quality. As mentioned, Chris at Octarine has new ones made to his specifications. No one likes having to a job twice due to inferior parts. RAY|
|Thanks for your replies, fellow MG Enthusiasts.|
I looked at the Octarine website. I think their studs are UK manufactured for them, but when I clicked on the photo of the studs and nuts and zoomed in they looked well rusted! Perhaps Chris could comment on this and maybe post some better pictures (if the actual studs were anything like the photo I wouldn't want them anywhere near my MG).
The ARP look good, although at 160 GBP (including tax and shipping) a bit expensive.
My reason for focusing my attention on the head studs is that I have recently noticed a drop in the coolant level, and I can't see any leaks; any guidance on what to check next would be appreciated.
"My reason for focusing my attention on the head studs is that I have recently noticed a drop in the coolant level..."
Let's focus on the coolent level change and worry about studs if we need to. Just what is happening with the coolent? How much of a drop, in what circumstances? If you have recently filled to the top of the header tank (ie to the bottom of the filler neck) I would expect the system to expell fluid at running temperatures to bring the level somewhere between a 1/2 to 1 inch level below the bottom of the filler neck. If this is all that is happening you would not have a problem.
If more fluid is escaping you might have a leak in the radiator, in either hose, or a loose fastening at an end to a hose for example.
Is there any sign of water in the oil? Or moisture exiting the exhaust? Can you give us some more information?
I check the oil and water levels about every 3 or 4 weeks (only been doing 10 or 20 miles a week in this car recently). When I checked the water level a few days ago it was near the bottom of the header tank. I was surprised to find this, as it rarely needs topping up. I topped up to an inch or two below the filler neck. After a 15 mile run the level had dropped by about 1.5".
There is no sign of water in the oil (on the dipstick, no emulsified oil under rocker cover). White stuff (condensation?) comes out of the exhaust for the first ten minutes' running on cold start-up; can't see any sign of water vapour or drips from the exhaust when the engine is warmed up. I always park the car in my garage which has a painted floor, so I would soon notice any water leaks from the cooling system.
I'll re-check all the above and measure the water level before and after a run (or maybe just idling on the drive for 15min). Can't do anything for a day or two, we've got torrential rain and high winds...
Thanks for that. I would be optimistic at this stage that you are probably not losing coolant internally, based on what you describe re oil and exhaust.
We probably need to clarify our respective radiator types. Mine is the centre fill, as per the 69 car build it is. I have a header space of perhaps 1" - to 1 and a 1/4" below the bottom of the filler neck to the top of the core.
My coolant level runs at just over the top of the core. Anything I put in above that (and on renewing coolant I fill to the bottom of the filler neck for the first run) always expels to leave the coolant level where it typically runs. I believe that is the way it should be on my radiator type.
I imaging something similar would apply to the earlier side fill radiator as well, though that might not be as visually evident (thinking about that, perhaps you have the centre fill as well because you mentioned the depth of loss?). If that is all you are losing, and the top of the radiator core remains covered, you probably don't have a problem. It depends on the depth of the space to the top of the core in your radiator.
Perhaps my first post wording has caused it, but you speak of both coolant and, latterly, water. On possible leaks, if you are running water and there is a tiny hole (radiator or hoses), or a clamp is a fraction loose, under pressure hot water can escape whilst running without necessarily leaving a trail. That may cease as the car cools sufficiently, perhaps before you place her in the garage?
Hope this helps. Let us know what you find.
Forgot to mention, my car is a 1980, which has the filler cap on a separate pressurised tank at the side of the engine bay.
The coolant/water I use is standard Halfords antifreeze diluted to 33% (this dilution protects down to -17c and boils at about 105c). The cap is 15lb (standard for late models); I have another identical one on my other car, so I'll swap them over and see if it makes any difference - I suppose they do fail occasionally.
When I return home, I always reverse straight into the garage (after opening the door, of course!) and the electric rad fan is often running as I switch off, so it's pretty hot when it comes to rest in the garage. A few weeks ago I returned after driving about 10 miles and when I turned off the engine I could hear a bit of hissing and gurgling from the front of the car (never heard this before or since) - maybe the pressure went above 15psi, or maybe the cap is faulty.
|Pinhole in the rad tube, water is evaporated by the airflow?|
|Art x2. Take it out and get it really warm (more than ten miles or find the nearest motorway and do one or two junctions) then pull the fuse on the fan, listen and look for the hiss. It'll be the rad or a hose. |
Silly me. Of course, you gave the clue to your radiator with the inch references to coolant change. I'm with Art and Mike on the likely cause.
|Brian. As others have noted, Chris's cylinder head studs are of excellent quality. If they are shown, in the photograph, as being rusty, I suspect that is a result of their having been through the "industrial, black oxide process". This is, otherwise, known as "bluing (blueing) in the firearms trade and is a controlled form of rusting. But, the two sets that I received from Chris did not demonstrate any surface rust and the one set I have used have held up quite well. But, under certain lighting conditions, a blued finish may show some reddish tints. |
As to the coolant loss. The first thing to do is to torque your current studs to the proper torque specification. My copy of the factory workshop manual shows a 45 to 50 ft-lb torque. Some years ago, a friend (professional MG mechanic for a number of years) demonstrated to me how the studs could, over a number of years, lose some of their elasticity, hence, require being retorqued, as part of a tune up process. He checked the torque on all of the cars he was tuning up as a matter of course. I was somewhat surprised, since I had seen no evidence of problems, to see that some of the nuts had to be turned a quarter turn to reach proper torque specification. As a result of this, I recommend your first action to be to check the torque on all of the studs.
The second thing I would recommend is the use of a "radiator pressure checker". This is a pump with a dial indicator, reading in pounds per square inch (PSI) and having an end fitting which clamps onto the radiator filler neck, or, in our case, the neck of the overflow tank. Run the pressure up to the rated 15 PSI and find out of the system will hold that pressure. If it will not, there is a leak somewhere. The radiator pressure checker comes with an extension to allow the testing of the radiator pressure cap. I recently tested my cap and found my 15 PSI cap would not hold 4 PSI pressure. Time to replace the cap.
Retorque the cylinder head and pressure test the cap and system. In the process you should discover where your problem lies.
"demonstrated to me how the studs could, over a number of years, lose some of their elasticity, hence, require being retorqued, as part of a tune up process."
No, the studs do not "lose elasticity" Rather, the gaskets flow under pressure and heat/cool cycling, leaving the nuts loose. I too check regularly, and have carefully measured some cars over a period of many years. You can expect movement, lessening over time, but the time can be years. It is more time and heat/cool cycles than mileage dependent. I have never replaced OE studs that were not visibly damaged, and I have never had a gasket failure. And I used to make a lot of money replacing headgaskets on cars serviced by others, especially dealers.
Chris' heads are actually done by Peter Burgess, Chris just builds the rest of the engine
|Fletcher. I stand corrected. You may well be correct, but I lack your experience in such things. Thank you for taking the time to add to my knowledge. It is appreciated greatly.|
Dom. Chris wrote me, a number of years ago, that he was having the studs made by a machine shop in the UK. While I am sure that he has the cylinder head work done by Peter (so do I--whom better--and my daughter's cylinder head was a piece of "table art" until I had time to install it), I do not know who produces the cylinder head studs that Chris sells. All I know is that the one set that I used worked much better than "Rover" branded studs I had previously used in my rebuilds, one of which broke when being tightened. I hold Chris in a quite high esteem. His recommended, and sold, products have never let me down.
|Fetcher is as usual correct. Cold steel does not "creep" under stress. It is a very high temperature phenomenon.|
|In my experience if there is any compression escaping into the cooling circuit with separate expansion tank that will pump coolant from the radiator into the expansion tank and eventually out of its overflow, thereby lowering the level in the radiator and engine, and that's with a small stream of bubbles. If the level in the expansion tank is dropping that is more likely a leak to atmosphere in the cooling circuit, which could be anywhere. One of the hardest to spot is when it is the heater matrix that is leaking, that's often only noticeable by misting or a sweet smell, but probably only in a GT.|
You don't need the filler neck adapter for systems with the remote expansion tank, just a Tee for the gauge inserted where the hose joins the rad and the tank, I made one for my V8 when I was having cooling loss so I could drive with the gauge in the cabin. I also used it to diagnose a bad cap on a 78 model, and like Les found that only holding about 4psi instead of 15psi, but the symptom on that was boiling during heat-soak after switch-off. The PO had obviously had problems before as he had fitted a mechanical fan to the water pump as well as the electric fan. The only problem was that the mechanical fan was blowing at the back of the rad while the electric was blowing at the front! You have to laugh ...
|I've owned my radiator pressure tester for 30 years and it has helped me locate minuscule leaks in the strangest places. Over half of the radiator caps that I pressure test fail at 1/4 of their rated pressure. Any service station, worth their salt, will have one of these testers and can check your cap and radiator in short order which will show you where the problem lies. RAY|
|John Twist demonstrated proper retorquing technigue by loosening the head stud 1/4-1/2 turn, then resetting to 45-50#. I dunno, cold steel over years and years of heat stretching and cooling contraction,can become somewhat annealed, and soften. Seems to me that "fatigued" stud, over time, will indeed stretch some as a heated head expands and pushes on it, and the owner retorgues time and again. I recall measuring some stock head studs out of a 300k mile engine and they were "longer" than the stock replacements from Moss by many thou. For the yard and a half from Dave Anton, I think the APT head bolt is a slice. Just my humble opinion. Cheers, VEM|
This thread was discussed between 13/12/2012 and 27/12/2012
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