The tale of Suspected head gasket problem
Here we go….. I’ve owned my Stag since 2006 and purchased it with a newish rebuilt engine. She has been a great performer until three years ago she developed a slight ‘shimmy’ on tickover and a vibration running at speed. Whilst inspecting the underneath I spotted a slight weep from the offside head, so suspicions were aroused. I also intermittently started to get a pressurised expansion bottle, even when cold. Talking to the experts the only way you can get a pressurised bottle is exhaust gases leaking into the water jacket. Ughh! Sounds like, looks like, tastes like blown head gaskets. No choice but to bite the bullet and have a go. Fellow club members Roger Phillips and Bill Fannon did their normal ‘rat out of a drainpipe’ impression, dropping their personal work schedules to help. Roger and I started on a cool but dry Sunday morning Bill joining us later. First job is to get the top of the engine clear of Air box, carbs, etc. I took photos of anything like the coil that had wires on it so that we know exactly where to put it back on rebuild. Just a little tip, take photos of anything where you could get parts the wrong way round. The banjo bolt for the servo vacuum pipe was ridiculously tight, no idea why! Perhaps whoever did it up had eaten three shredded wheat for breakfast. Inlet manifold next. Not all of the bolts have socket access so a couple need to be spannered out.
Pile of bits so far. (hope we can remember where they all go) Next we start removing the studs. If you’re going to have a problem, this will be the likely culprit. Depending upon how long the studs have been in and how they were put in, i.e dry without some sort of protective grease such as copper ease or molybdenum grease. They can be very reluctant to come out. Normally because they’ve ‘welded’ themselves to the head. Getting the special tool off the extracted stud. Fitting the outer part of the extractor to the stud. NOTE always remove the big washer under the nut head, as this gives you close to an extra 1/8th of an inch of thread to go at.
Fitting and tightening the inner part of the tool against the outer part, this locks them together and onto the stud.
To remove the stud you simply undo the outer part. Such a simple word ‘simple’. 6 of the 8 studs came out without any drama at all. For the mathematicians amongst you, you’ll realise that two of the little blighters didn’t come out nicely. The next job was to drop the exhausts off the manifolds. For this you need a special flexible tool, in the form of my lad Sam, 28 years old and a damn sight more flexible than either me or Roger. We aligned the timing marks on the cam shaft sprocket with the cut outs on the first retaining cap, to ensure No 2 pot was on TDC. This was not absolutely necessary for my job as I’m replacing the timing chains anyway. If you’re not replacing timing gear you need to lock the cam sprockets onto the guides within the cover before removing the sprocket from the camshaft to stop the tension of chains etc being lost. The following picture shows the sprocket retained into it’s guide.
Knocking back the tab washer to enable us to remove the sprocket. NOTE the cloth to prevent any stray bits of metal dropping into the covers and consequently the sump. Next we undid the two bolts and remove the sprocket.
Nearside head off. Note the rear stud still in place, one of the two little blighters. We stillsoned it out after successfully removing head, we had very little clearance to get it off with the exhaust manifold still on the head. At one point we thought we’d have to remove the manifold BUT luckily there was enough room, just! In case any of you are wondering we didn’t use the chisel to remove anything, it was just used as a wedge. On the offside head the rear stud once again refused to budge using the extractor tool or two nuts together, so we eased the head far enough off to get the stillsons in to break the studs hold in the block. Bill, who has immense experience in engine work has never seen a stud stuck this hard in a block before. Just goes to show, you’re never to old to learn something new. With radiator out, next job was to free off the front cover bolts and remove the cover. We were lucky and it came away from the sump gasket without damaging it. We were prepared to simply replace that front cover section of the sump gasket and sealer if we had damaged it. As it happens when we replace we’ll simply put a bit of sealer for added comfort. The timing gear etc is pristine, so we’ve decided only to replace the chains. There is absolutely no wear on sprockets, guides etc.
Now for the proof that the head gaskets had gone…… No 3 Cylinder outer edge, no wonder there was a little drip coming from there. No 7 Cylinder showing damage to the rear edge. No 4 Cylinder showing signs of creepage. Note, on a compression test the pressure on 4 was well down, BUT on inspection of the cylinder there’s no sign of damage so we’re hoping we’ve got a dodgy valve or seat. Bill has the heads so we’ll know soon. No 8 Cylinder showing signs of failure. MORE TO FOLLOW AS WE PROGRESS – Come back for part 2 – Head cleaning and prep.
PLEASE NOTE – these are NOT instructions on how to undertake this job just some pics and words of our experiences, always consult professionals when undertaking any repairs or restorations. (please refer to the disclaimer on our about page)