Well I had some white smoke from Bank B so thinking this was a blown head gasket, I’ve pulled the head.
I did notice some signs the head had been off before: one stud not was chewed and there was copper grease on some threads…
This probably helped in that the head came straight off, well it took maybe 30 minutes of rocking the head and spraying lubricant down the stud holes but no special tool needed or anything (hope the other side is so easy).
So, I was expecting more obvious signs of damage to the gasket and it looks ok to me. However some work would be needed before reinstalling the head.
What do you V12 experts think of the condition of the head and gasket? I think I would definitely have the mating surface machined nice and flat. I’d clean the valves, grind them in check intake and exhaust valve clearances etc (and set them to the recommended clearances).
Or may take the heads in to a specialist to rebuild the heads.
What puzzles me though: I removed this head due to white smoke coming from this bank. Does this head gasket look blown? There is some rust on the mating surface and the studs are a little bit rusty.
Any tips for cleaning the studs and , dare I say it, the pistons without disturbing the liners?
Like Kirbert said, that head has been off before. The fact you got it off in 30 minutes with little effort is a giveaway and the squeaky clean tappet block is unusual for such an old engine.
Do not rush having the heads skimmed. I would get a piece of metal bar or even hard wood, wrap a bit of fine wet and dry paper or very fine emery paper around it, and just clean up the surface.
The first thing to check is the fire rings around the combustion chamber. They must be in 100% condition, no compromise.
Next is the outer edge of the head and a couple of oil holes. They can be a bit less than 100% because they are not under high pressure and the head gasket should have a reasonable bead of sealer to deal with any minor imperfections. Plus you can add a touch of sealer if needed.
You might be lucky. There is still a question of valve gear and seats to check out.
I am rebuilding an HE V12 from the mid 80s. Poorly maintained engine, the heads took for ever to remove and proved to be only for scrap. In desperation they could have been saved but needed a lot of work, and you can’t skim too much because it affects compression ratio and the chain run.
Luckily you can still buy brand new HE heads at a decent price.
I have not seen brand new pre HE heads anywhere, but they might exist. Is so could be a better bet than refurbishing what you have.
There is the next major decision. Do you totally strip the engine, or just bother with the heads ?
Did you do a compression test before engine strip? You can measure for bore wear with a “rockit “ gauge. If the studs are just surface rust, wire brush them after masking off the bores to prevent rust getting in them. I usually consider any stud that the diameter is seriously corroded away - normally at the point close to where they enter the block. This is the area where the corrosion gets bad ,as the stud is then close to the aluminium and the electrolytic action is worse for some reason.
Also do your best to dry out the cylinder block waterway before wire brushing. You can then get out the dust using a vacuum cleaner or preferably an aqua vac.
Ref head skim ,if you do one you should do the other I can’t seem to open up your photos, so can’t really inspect the head face?
I’ve never refitted a head since rectifying faults one basically new engines back in the 70s/ early 80s. Without the head face being skimmed.
Hard to say for sure from the pics, but I do notice some oddities in the head gasket on the top side at 1B, and that 1B’s sleeve/piston top seems wet with a super clean spark plug in the head. That could be due to over-rich gas washing, or a cleaning effect from coolant ingress (but it doesn’t seem to have been happening long enough to really clean the cylinder or create green residue on the plug… so… ???
I echo not having it skimmed immediately. A good cleanup plus straight edge check is in order.
Ideally pre-checks like compression, leakdown, and coolant-system leakdown would have been done first, but it is where it is.
Thanks for your replies so far folks. I’ll take closer and better pictures later today.
Basically I think I got a good car here. I just realised some pitting is not the end of the world in these heads because the head doesn’t sit flat on block surfaces like the V8s I’ve had apart.
I’m going to work out how to make my own liner clamps so I can clean the pistons and bores.
If I use cleaner like carb cleaner will that end up taking the oil of my bearings? Obviously I want to keep the film of oil in there for start up time as there will be a few seconds before the oil pump starts getting the oil round.
I didn’t do a compression test. I found one in the history a few years old but within very few miles that remarked cylinder 6A is low even after putting oil down the plug hole, indicating maybe guide or valve let by (?)
I should be able to deal with that when that head is off.
Hi Paul the plug cannot be relied on as I removed the plugs and cleaned them and they’ve all gone back in different positions just to stop anything falling down the bores when the engine is out.
1B does have some oil in there. Also it turns out three injectors were bad and dripped fuel as long as they were under pressure. This was found out when I just had the injectors rebuilt but the engine won’t run with these injectors yet.
A preliminary clean of the head surface with a scotchbrite cloth and carb cleaner brings it up nice. Nicks in the head surface are presumably from when it was originally removed sometime in the past.
I sprayed some carb cleaner then petrol onto the piston tops and gently touched them with a soft brush. The carbon and oil virtually disintegrated at the softest touch. I dropped a cloth into each bore to soak up the cleaning fluids. That’s as far as I want to go as I do not want to disturb those liners. If the carbon is this soft I presume an Italian tuneup will blast it out anyway. Bores feel dead smooth (touching very gently). The fluids didn’t sink past the rings so presumably that’s a good sign?
Next: I hope the other head comes off as easily. Then I’ll work out what I can and can’t do regarding checking specs for the valves etc, though I really do want to set the valve clearances so I can set them ideally and have experience of doing it.
At the very minimum I’d have a shop hot tank the heads to clean them.
Still wondering now where was the white smoke coming from at Bank B? Maybe it’s brake fluid? Injector rebuild revealed 3 injectors that dripped fuel as long as there was any pressure on them but I didn’t note the injector positions before i removed them. The valves that are protruding don’t feel like they have any real movement side-to-side though I guess they are under spring pressure. Will check when I separate the tappet block.
Head gasket is nice. Surface machining of head looks kinda coarse to me. Maybe I’ll have that done smoother?
Malc.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
13
You might want to disturb the liners. With the piston at TDC, slide one liner up just far enough to clean up the ledge under it and the underside of the step on the liner. Apply some Loctite 518 and slide it back down. Repeat 11 more times.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
14
Malcolm, since your engine is a pre-H.E., you can have the head milled and it won’t affect the compression ratio. It does affect the compression ratio on an H.E., which may color some opinions on having it done.
Perhaps more importantly, though: On every photo of a pre-H.E. I’ve seen, there’s a little recess surrounding each valve. There are reports about how much power can be gained by either smoothing the step down into that recess or milling it away completely. I see no such recesses on your head! I’m sure others will chime in here, but I suspect your head has already been milled to the point of erasing those recesses. And that might mean you don’t want to mill it any further, as it might be getting thin in places.
None of that looks bad to me. I doubt there is warpage, but it should all be checked with a straight-bar, back-lighting, and a feeler gauge (if needed) anyway.
Add a little oil or break-in lube to the piston ring area before refitting everything. Generally really good cylinder liners still have their cross-hatch hone marks and no real lip at the top from where the rings stop. Also no linear marks in-line with the piston movement direction.
The nicks are only critical if they are on the fire ring.
The machining marks you think are coarse do look a bit rough for ex-factory quality.
Chances are the head was skimmed by a workshop not so fussy as you would like.
Cross your fingers the other head comes off easily.
I rig up a container of oil feeding into the hole where the oil pressure sender fits.
Leave it a couple of days and that will prime the oiling system before the first crank of the engine. Plug the hole before cranking of course.
Thanks folks. Kirbert I looked at photos of other heads and they are like mine, at least the early ones and E-Type V12 heads.
Paul: The bores feel really smooth but there is an edge of carbon near the tops of the liners. There were some oil signs like in Bank B air box however I don’t know if the PCV is OK. I cleaned that and the mesh filter as the mesh one was solid with oil and probably blocked.
I’m being careful touching the pistons but they clean with carb cleaner and petrol very easily and the domes look nice. I may not attempt this on e other side because I think disturbing a liner would not make my day. I took the engine out to make painting the bay easier but the heads are only really coming off as I had white smoke from one bank and if it wasn’t for that I would have left the heads. I have no reason to suspect any other problems. My tensioner didn’t even explode when I was attempting to take the tension off. However in case that is 44 years old I will be replacing that and the chain.
Great tips thanks folks, especially on priming the engine with oil.
As for the smoke, jury still out? I wasn’t surprised to find some sludge remnants in the sump. However this was quite hard to remove as it was semi-solid making me think it was from some time ago. The oil drained out of the sump without any traces of water in it and was fairly clean. The coolant was bright green.
I had to take the sump and sandwich plate off anyway as I wanted to remove the timing cover and the gaskets were a bit leaky. I couldn’t imagine doing this with the engine in place. I think it’s worth the hassle of taking it out as everything is a lot easier to do after that!
The head face looks really good. Nearly every head you take if has more corrosion that yours. Check the face is true, might be worth getting the heads pressure tested? Look for any sign of water traces where they shouldn’t be. Valve stem wear? No,you can’t check this with springs still in situ.
Thanks the other head is off and not so easy to clean as it looks like an inferior head gasket was used there. That gasket has degraded quite a bit and rusted. I tried to separate the tappet block on that one and it doesn’t want to come apart. I’ll need to get the tappet blocks off so I can clean and check the valves.
The tensioner is an expensive item.
Don’t buy one yet, check the one already in the engine.
It might have been replaced before.
I scored lucky with the HE I am rebuilding. Although a dirty mess it had a virtually brand new tensioner.
