DIY Head Gasket Change tips and tricks?

[mole42]

There is an instruction in one of the Triumph documents that Stag heads should NEVER be skimmed. Of course, in those days you could buy new ones.

[Tdm]

There is an instruction in one of the Triumph documents that Stag heads should NEVER be skimmed. Of course, in those days you could buy new ones.

Not seen that myself Ian, and find it strange.

In 23 years of ownership I have had my Heads skimmed twice in fact, the last time being in 2005 and it doesn't seem to have done any harm, touch wood, 13 years having since passed and the car is currently running better than ever.

Both skims followed Head Gasket failures.
The first skim being done in North Wales (in Mochdre) in 1998, when I also had hardened exhaust valves fitted,
and the 2nd "light" skim was done locally in Tenerife 7 years later, and cost me just €€70 Euros for the 2 Heads.

I did have the Garage who were doing the 2nd one check whether it could afford another skim, and they said Yes,
but only a light one and that would then be it.

PS. Note for Admin - the new version of vBulletin will not print the Euro symbol!? When I type it (Ctrl+ Alt+ 4) I get this €(nothing at all).

[Ian928]

Ok, I have been Googling and it seems my car has County Pistons. There is nothing on top of the pistons telling if they are oversize. I look at a picture of oversize County pistons in the Rimmer catalog and these have no markings. Do oversize County pistons have any markings?

The reason I am asking is because I am afraid this engine need to be rebored. See the pictures. The corrosion is easily felt with finger. What do you guys think?

[Ian928]

Ahhh... forgot to add pictures, cant insert pictures in the Edit mode it seems?

[jagorstag]

PS. Note for Admin - the new version of vBulletin will not print the Euro symbol!? When I type it (Ctrl+ Alt+ 4) I get this €(nothing at all).

Hi Terry,

Looks ok to me, I can see the euro symbol correctly in your post. However, when I read it in the quote it looks just like a square box for some reason....

Cheers,
Joakim

[flying farmer]

I would start by getting a good steel ruler with a straight edge and a set of feeler gauges. Clean all the crap off the head and block faces and see if you can fit the thinnest feeler gauge under the edge of the ruler at any point on the block and head faces.
Pay particular attention to the areas between adjacent stud holes in both the block faces and head faces, particularly at the rear of the block.
I have come across a supposedly reconditioned block where the head studs had previously been so overtightened that it had raised an area around each stud hole in the block face. Fortunately I discovered it before I put the engine together, the gaps between the stud holes were about 3 thou deep suggesting the block face had been pulled up by this much.
The corrosion pitting does look like it has been there for a while, and doesn't look very good particularly on one of the pictures.

If you find any warping of the block face it will be a complete strip down job, and it would be sensible to get it rebored at the same time given the state of the bores.

[Guest]

If you find any warping of the block face it will be a complete strip down job, and it would be sensible to get it rebored at the same time given the state of the bores.

This ONE OFF post should serve as a warning.

1/
I had exactly this problem on my YB Sierra Cosworth I bought in France.
The engine was mostly in the boot, as the French invariably do when they give up.

The numpties at all the (French) engineering shops kept slicing more and more off the head, cos it kept blowing gaskets..
..then they had the nerve to call it a "sh..t British engine" and "d mn unreliable crap", when all they failed to make it work properly,-

all they had to do, after nearly destroying/overskimming a perfectly good cosworth head was to check the block face.

Einstein's definition of insanity worked perfectly here.

The block deck was at least 3-5 thou out of true, which was probably a fault at FORD improved by the local hoodie garage owner's son thrashing the living daylights out of the car every day for 3 years.
Once I had taken it to bits, machined it all, made sure it was all perfectly flat, it went back together and ran like a swiss watch.

2/
I'm fairly sure from seeing the state of the block on Mick's Stag V8 engine, (also relinered after being rebored umpteen times), that they (nobody) could never be bothered to check the V was actually 90 degrees, and that the trueing of the block deck/datums of the main line to top deck to bottom deck and the 45 deg angle of each side of the V are vital.

What was astonishing was to see how someone was perfectly prepared to assemble it all like that wasting time, money and energy.

Once I got our guys in Wootton Bassett to sort it all out (they rebuild Bentleys), the engine has been running like a Longines ever since.
I had complaints at the time...why drive 95 miles to Wootton B when there are lots of engineering companies in London?
Yea right!

In fact it's one of the most reliable stags I am told being thrashed around the UK & the continent, constantly.

I saw a Dolomite 16V engine once that had very similar problems.
Not one single flat face on the block was actually in its correct line related to the others....
The thing was like a cheese.
You can use a cheap laser these days to spot all this stuff more or less instantly.

3/
We had a similar thing some 20yrs ago with an Austin Healey 100-6 engine, which had been rebored and linered umpteen times, and each time it burnt out the pistons..
(In Germany we call this a KOLBEN FRESSER).

Turns out at the factory in bloomin Abingdon, they had bored the mainline originally AT LEAST 3-5 thou out of true with the vertical datum line of the block with the main error at the rear end of the block, which meant it was those that had the most misalignment.
Nobody could ever find out why, so Einstein's definition of insanity was held by several French garages, - a world record.

In effect it meant none of the 6 pistons was actually going up and down aligned with the bores with the last 3 being worst of all..
My question to Steph, the guy rebuilding the engine once again was,-...

..t'as verifie la ligne paliers?? (did you check the main-line)
to which he replied "pourquoi" (why!). Ahum 'nuff said!

So, I told him forget building that heap of junk, take the block to Paris and have the main line honed to correct it...
He did that, annoyed like mad because it's 650kms there and back, and it costs a lot of money.
Our engineering guys in Paris had rarely seen a block with a mainline so badly out of true, it was a wonder it ran at all!

When all that was done and dusted, the engine has never missed a beat ever since, and is still going well (non std cam and head now) to this day....

[Ian928]

Thank you Flying Farmer,

I will check the block as you describe. Maybe you can answer some more questions?

1. Can I turn the engine with the cam chains supported only by the pedestals? I would like to check all the bores.
2. It may be that I have been running the engine like this for a long time. There was water in the oil last spring at least. I am not sure how all cylinders should be affected though? From cleaning the bores after disassembly I think cyl no 8 was the likely one to be leaking. This cylinder did also have the highest compression before testing, do you think that could be because it had water in it when testing (sealing piston rings)?
3. If I understand you correct, you think that the engine can be run like this. IF I decide not to rebore, do you think I should clean up the bores a bit with a fine grade (or maybe not so fine?) wet and dry or just keep it as is?
4. From googling I think I have County pistons. I understand that they are not very good. I also understand that County pistons is the only readily available piston. So if I decide to rebore I wll not end up with inferior pistons to what I have now. Can you confirm If I have County pistons?
5. The most important question may be if I should get a refurbished engine from UK instead of trying to fix my own here in Norway. Wages are high here, a regular garage typically is around £100/hour. If I do the disassembly and assembly myself and just do the reboring and resurfacing of the heads I may get away with £1500-2000 I hope. Plus parts of course. And I do not know the state of the crank for instance. On the plus side, it sems the heads have new valves and guides. On the minus side, all plug threads are are damaged to a part...

I would start by getting a good steel ruler with a straight edge and a set of feeler gauges. Clean all the crap off the head and block faces and see if you can fit the thinnest feeler gauge under the edge of the ruler at any point on the block and head faces.
Pay particular attention to the areas between adjacent stud holes in both the block faces and head faces, particularly at the rear of the block.
I have come across a supposedly reconditioned block where the head studs had previously been so overtightened that it had raised an area around each stud hole in the block face. Fortunately I discovered it before I put the engine together, the gaps between the stud holes were about 3 thou deep suggesting the block face had been pulled up by this much.
The corrosion pitting does look like it has been there for a while, and doesn't look very good particularly on one of the pictures.

If you find any warping of the block face it will be a complete strip down job, and it would be sensible to get it rebored at the same time given the state of the bores.

[flying farmer]

It is ok to turn the engine with the cam sprockets bolted to the brackets. There is a possibility the timing chain tensioner will click out a notch and prevent the sprocket re aligning with the cam if you don't have to strip the bottom end. This hasn't happened to me (yet) but it depends on how well the brackets support the cam.

Water in the no8 cylinder could raise the compression by filling the ring gaps and the gap between the piston and bore above the top ring.

Whether you can get away with running the engine with the pistons/bores as they are rather depends on how it ran before. It is difficult to tell from the pictures how bad they really are, but if it ran with no smoke or bad oil consumption it is a possibility. Without being able to remove the pistons completely and hone the bores the full depth it is pretty pointless sanding away at the exposed part of the bore.

I wouldn't worry about county pistons, I have never heard of any problem with them unlike JP pistons (the only others currently available) which have a rather unfortunate history of seizure and excess weight. The first engine I built came with county pistons and showed virtually no signs of wear after 70,000 miles of hard use. I have a set of +20thou county pistons in the shed, they have COUNTY cast into the inside of the piston skirt but no markings on the crown other than the arrow indicating the front of the engine and 020 stamped in the piston crown. The fact yours have no stamp suggests they are standard size so may well be original pistons.
I suggest you ask for a few quotes for reboring and skimming before you decide what to do with your engine. I would not be surprised if the heads did not actually need any skimming, if the engine has not been overheated since they were last done. You can buy complete rebuild kits from the likes of James Paddock or Rimmers which should give you an idea of likely costs apart from machining. If you have to strip the block you will find out what the crank is like.
As you say, labour is the biggest cost, so if you do have the time and ability to strip the engine you can save a big amount plus you can measure and look for faults in your own engine. If you buy a ready rebuilt unit you can be buying some real horrors, Someone I know bought a reconditioned short engine that had filler in the corrosion pits in the bores and the surface of the crank could have been used to grate cheese!

[Ian928]

Ok, so I have decided the engine should come out to be rebored. I checked the straightness of the block and around cylinder 8 (where I suspect I had a HG leak) I was able to fit a 0.05mm feeler gauge. I will have the top of the block skimmed also.

Any tips to remove the block without heads?

[flying farmer]

Why not loosely bolt the heads back on, the exhaust manifolds make a good lifting point if the power steering pump lifting point has been removed.

[Ian928]

Why not loosely bolt the heads back on, the exhaust manifolds make a good lifting point if the power steering pump lifting point has been removed.

I found a post where someone used a strap around the block behind the engine mounts. Looked OK to me, although not vertical when suspended free. I guess I will complete the engine out of the car so I can use the original lifting points upon installation.

Attached is another horror picture from cylinder no 2. You can clearly see a imprint of these scratches on the Head Gasket. The Workshop clearly knew what they were doing when they put the engine together like this.

[flying farmer]

Just what is needed, great deep scratches that cross the fire ring of the gasket, a very effective way of getting combustion gasses into the cooling system. One of the reasons Stag engines have such an appalling reputation is the amount of horrible bodge jobs done on them over the years, then people are surprised when they fail repeatedly!

[dasadrew]

I found a post where someone used a strap around the block behind the engine mounts. Looked OK to me, although not vertical when suspended free. I guess I will complete the engine out of the car so I can use the original lifting points upon installation.

Jumping swiftly to the disassembly which took place over winter, the major challenge was finding the right size tools after having spent 30 years in the metric car world.

After much debating on the best way, the engine finally came out after removing the gearbox- Major snag was the width and length of the Stag engine bay. The hoist just didn't really have the proper reach and I'll have to fabricate a jib extension to get the lump back in - probably with gearbox and O/D attached.

[ATTACH=CONFIG]8097[/ATTACH]

That's a nuisance - quoted photos don't show. It's one of the first posts in my White/Blue Bavarian Stag thread

WEB ENGINE LIFT 02.jpgWEB ENGINE LIFT 01.jpgWEB ENGINE LIFT 03.jpg

[Ian928]

Does this mean you recommend removing the gearbox first then lifting the engine horisontal? My lift look to be similar to yours.