advice on cylinder head please!

I'm told that coking is pretty normal, I was surprised when I dismantled an engine for the first time and found that three cylinders were black with soot and coking while one was clean. As it turns out, the clean one was the problem as its very cleanliness demonstrated, washed by a coolant leak.

As for compression, if you've got a step in the bores then that signifies wear, which if it's large enough it could cause exhaust gasses to get into the crankcase (as it did in my case) but I'm not sure if that's enough to lead to a drop in compression. The bores becoming oval through wear might do I suppose. I used to get a lot of oil in the air filter, it was coming up the crankcase breather hose into the air system and being sucked as mist round to the filter, this was happening due to the exhaust gasses blowing past the cylinder into the crankcase. This was on a non-landy engine though.

Hopefully someone will tootle along later on and know your particular model of landy engine well, all the above is just FYI.

Was this a general loss of compression on all cylinders or on one/two cylinders only? Remember that there is not much compression on these things, anyway. What was the reason for strating this investigation?

Whilst you've got the head off why not inspect/grind the valves? I've had two cases of chunks out of exhaust valves. This whole area is another potential compression loser.

I don't imagine that the wear in the bores is anything to worry about. What you describe is fairly normal when a few miles have been accumulated. As long as all cylinders are equally oily (preferably not oily!) you can probably also rule out broken piston rings. Any other symptoms like burning oil or high crankcase pressure?

Is the blackness oily?

The blackness is dry soot / carbon. It's rubbing off quite nicely with a non-metallic pan scourer. The bores are clean without any major scoring.

Last compression test was about 2002, just before it laid up for about

3 years. At the time the outer cylinders were about 7, the centre two about 5. I suspected the gasket between the two centre bores. It ran a bit rough, a bit smoky, but would still pull 60 mph+, so I didn't fret about it. The more I ran it, the better it got.

Now back with an MoT, it ticks over OK but only if running quite rich. It also produces bugger all power - only just enough to move itself in low ratio. So I decided to lift the head and see how things looked, expecting a buggered gasket. The gasket isn't great, but it is all in one piece, just a few little splits and cracks, but nothing right through.

I'll have a look at the Haynes and see if the valve grinding looks to be within my skill set!! Now it's apart I want it to go back together as good as it can be without spending money on it. If I'm going down that route I can be trailered to Warren for a remanufactured engine. My ethos on this truck is that I either botch it cheap at home or really sort it properly.

Thanks for the advice - the valves, incidentally have a variety of little dots on them. Some have 1, some 2 and one has 3. Does this signify something?

The cylinders/bores don't sound too horrible - probably not even horrible at all - from your description.

I'd look at taking the valves out of the head, cleaning up the crud which I suspect is partially blocking the airways (caused by cold running, valve stem oil leaks etc.) and grinding the valves.

Dots on the valves - probably marks made by those who have had the engine apart before to indicate from which cylinder each came.

Grinding the valves in is not a difficult job (getting the head off is much worse) provided you have the necessary tools ,a "G" clamp with two prongs to compress the valve spring so you can get the cotter pins out which will then fly everywhere, and it's one job I would certainly do as a matter of course if you have the head off. It also allows you to check the valves for soundness, no chips or dents on the rim etc which could be your problem, the springs for soundness, and to replace the little rubber valve stem seals which will cause smoking if old and knackered.

That said, if you are going to go down the road of a full professional rebuild don't bother.

Thanks Bob - that's what I'm trying to avoid. I don't plan to do a pro rebuild on this engine - if I can't get this one right then I'll simply swap the lot for a new one. Getting this one right will be a whole lot cheaper, and more rewarding!

Right - quick dash to Halfords before closing to get a spring compressor!

It's certainly worth doing a full decoke, grinding the valves in, checking the head for flatness - use a good, new steel rule and a feeler gauge - and re-assembling with a new head gasket. The cost is low and will eliminate gasket trouble, valve trouble and a warped head. If it still isn't giving good compressions then you're looking at a more expensive rebuild, possibly rebore etc etc, at this point you should be seriously considering a professional rebuild or a recon engine (unless you fancy doing it all yourself.....)

One point, if you can't get good compressions after doing the head, take an oil can (one of those with the plunger) and pump 3 or 4 squirts of oil into the spark plug hole, refit the compression tester and test the compression again. If the compression gets significantly better then suspect worn rings/bores - rebore/recon time.

Alex

Black is normal for the combustion chambers of this engine (or any other I've had apart for that matter) and will have been made worse by the fact it would only run rich - as long as it is the same on all cylinders and not oily. Along with others I agree that you may have poor valve sealing - I don't suppose you checked tappet clearances before taking it apart? With valves reground and checked and cylinder head flatness checked and a new gasket, the only remaining source of poor compression will be broken or worn rings (or excessively worn/scored bores, which you appear not to have) which usually show as crankcase pressure (oil leaking everywhere) before engine performance gets as bad as you report. You may have had valves sticking as well as poor seating. Once the valves are out it is possible you may find it bad enough that you need new valves or even seat inserts fitted (the last is not a home job!) JD

"Tim Hobbs" wrote ... "Bob Hobden" wrote>

Did I say Cotter pins !!! I must have had too much to drink.

"Alex" wrote

Would it be worth his while replacing the rings anyway while he has the head off? Provided Tim feels happy doing that. I say that as a friend had a Diesel 2.5 NA that started to smoke a bit and he changed his whilst doing the head and valve stem seals etc. Reckons it's made a noticeable difference to the engine as some rings were well stuck in the pistons.

First, do not use a chisel, screwdriver, knife or any other sharp tool to get the gasket off. I've found that a Dremel-like tool works best.

Second, make sure that you take the head to a machine shop so it can be milled. Anytime, cylinder heads are removed from the block they will warp. Explain any damage the machine shop and why you removed the head in the first place. More they know the better the job you get.

Third, use the highest quality head gasket available. I have always had success with copper shim type gaskets. Those are generally found on high compression, supercharged and turbocharged engines.

Fourth, run a straight edge (such as a machinists ruler) across the top of the engine block. You're checking for any warping of the block itself. You may [or may not] have to remove the block for the shop to work on it.

I started off with the hairy stuff at first, Eh? You didn't mention what the engine was, petrol or diesel. If petrol, any backfiring? If so, fouled plugs, ignition wire gone bad, distributor/rotor needs replacing. If diesel, a lost of compression through a fault in the head gasket, oil blow by on the piston rings, timing belt/chain out-of-wack.

If you have a diesel and you're close to a seaport, such as I am here in Norfolk [aka Hampton Roads] Virginia, a marine mechanic could be quite a bit cheaper than your local Land Rover dealer.

Sorry, folks but the local dealer has tried to rape me when my wife brought hers or I brought mine in. My son learned from my experiences. Just my quid's worth of knowledge.

Cheers.

With the 2.25 Landrover petrol engine the head will not be warped unless it has been cooked, and there should be no need to have it machined. We are talking about a very robustly built low compression engine here.

This engine is neither high compression, supercharged nor turbocharged. Any good quality gasket will be satisfactory provided the head is not warped and the mating surfaces are clean and undamaged, and the head is tightened down correctly and retensioned at around 1000km.

He says clearly it is a 2.25 petrol engine.

(snip)

JD

That's not terribly inusual on engines of that age, indeed de-coking used to a fairly routine operation - hence top-end sets are often referred to as de-coke sets.

The 2¼'s will take a fair bit of abuse, so a step is not the end of the world - it does need to be measured though to check it is in tolerance. Look of the sides of the bores for signs of blow-by, i.e. gas passing the piston rings. Black/discoloured "scorching" indicates ring/bore problems.

While you have the head off, strip it down and check the condition of the valves and valve seats - there should be a nice shiney ring round the valves and a corresponding one on the valve seat - any "gaps" mean the valve is not closing properly which will give low compression. Also check the valve guides for wear. The Haynes manual gives the required info. Having got that far, you may as well get the head skimmed. Also check the condition of the rockers - particulary the bits that make contact with the push rods - and check the push rods (roll them on a flat surface looking for kinks). Also have a look at th valve springs - line them up on a flat surface an see if they are all the same length. The springs are not over-critical on a 2¼ pertol, by one school of thought says replace them anyway having got that far (94p each).

Assuming all is well, and you intend running the engine again for a while, you might consider having "unleaded" valave seats put it while the head is away - not least as you get to avoid lapping the valves yourself that way!

Richard

more than me, but they sell

revved above twice idle

Cosworth on a 60hp LR engine!

On of the professors when I did my eng degree had a favourite mantra...

"Any fool can build a bridge that will stay up. It takes an engineer to build one that only just stays up."

The gasket that came out is a copper one. I haven't even looked at the new one in the Britpart kit, but it's a forty year old engine with very low compression even when new. I don't think there is any benefit to anything remotely exotic in this instance.

There is no sign that the head is warped, nor the block. I have, however, done a Yell search and found a few workshops in reasonable distance that can rebuild the head. So I'm quite confident pulling it apart :-)

My decision now is whether I should just have the head fully rebuilt and be done with it. There doesn't seem much point, given that I can buy an exchange one from Turners. It's not an original engine - the car is a real 'bitsa', so there's no need to keep the original pieces.

If the block is worn, and I put the new head on it and still get crap compression it won't be lost money, because I can then get Turners to put the head onto a new block for me.

I can see where this is heading....

Changing rings is a rather more involved job, the only things you don't take off the engine when doing rings is the front cover and camshaft.

Personally, I'm very reluctant to change rings on thier own, if the rings are worn then chances are the bores will be too. And for that sort of stripdown you might as well be looking at doing everything, as with the crank out you can inspect the mains, which on a 3-bearing crank will probably need doing anyway.

Alex