P1B6929BW 3.4S auto

[paddyx350]

So completed a compression test;

No 1, 115 Psi, No 2, 120 Psi, No 3, 120 Psi, No4 120 Psi, No 5 120 Psi, No 6, 110 Psi

With 5 ml of oil added to the cylinder the compression on all cylinders increased by 10 Psi.

[cass3958]

Was this on a warm engine or cold Chris?

Personally as I said before I would be looking at 140 to 160 psi across the board. The fact you have 110 on one and 120 on another suggests wear but it could also suggest that not having run for a long time the valves might not be seating correctly or that the piston rings are stuck. Either way personally I would whip the head off, regrind the valves, and check for wear in the bore.

Before doing that though because you cannot get to the piston rings without taking the bottom end out I would pour some white vinegar down each plug hole and leave it for a couple of days to really soak in. White vinegar is a mild acid which will free up the rings and possibly remove a lot of the coke build up in the combustion chambers and certainly get rid of any rust you have in the bores. After a couple of days turn the engine over with the plugs out and all the white vinegar will be spat out the top. Then refill the plug holes with some diesel oil and let that stand for a couple of days before removing it the same way. After all this try another compression test and let us know the results.
The white vinegar will not damage the engine but it might soak down into the sump past the piston rings so before you start the engine it would be correct to do an oil change.

[John Quilter]

And after doing all that, if the engine runs, I would run it for a while, if driveable, I would drive it for a while, 20-30 miles and then redo the compression test.

[paddyx350]

The compression test was with the engine warm, (30 Deg C) on the temp gauge but probably not up to full operating temp which I understand from reading the service manual is 70 Deg C or thereabouts. Also didn't do it with WOT either.

So I redid the test this afternoon, letting the engine warm up completely and with the accelerator on the floor. I gave the throttle a good few blips during warm up and did get a good bit of blue smoke out of the pipes, but this could, I suppose be the 5 ml of oil I put into cylinder to do the second set of readings I took on Friday.
The results improved a (very) little.
Todays reading are first with Fridays (the ones before the 5 ml of oil was added to each cylinder) in brackets;

No 1, 120(115) Psi, No 2, 125(120) Psi, No 3, 123(120) Psi, No4 123(120) Psi, No 5 123(120) Psi, No 6, 115(110) Psi

I'll now do as suggested with the vinegar and diesel.

How much white vinegar/diesel per cylinder are we talking about? A tablespoon?
The car has no brakes so it's not safe to drive unfortunately, but will redo the compression test with the engine fully up to temperature.

[cass3958]

The vinegar will not damage the engine so get the pistons to half mast and then fill each pot with as much as you can get in. Let it soak for a couple of days. Technically if the rings are good none of it should pass down in to the sump. The main reason for sticking piston rings is a buildup of carbon, old oil and fuel that has turned to varnish. The vinegar breaks all this down and leaves clean metal.
Once soaked lay a towel across the top of the spark plugs with all the plugs out. (Do not turn the engine over with any fluid in the piston pots with the plugs in. Mega damage can be caused,) and crank the engine until all the vinegar has been pushed out of the spark plug holes. If you use a white towel you might see how dirty the fluid gets as it comes back out. Repeat with the same amount of diesel and let it soak a couple of days. Empty the same way. Once you know all the piston pots are dry replace the plugs and fire her up. Lots of sh*t and blue smoke will come out of the back which is expected.

White vinegar can be used to clean the inside of your radiator and waterways or even fuel tanks that are rusty on the inside. I cleaned both my fuel tanks with white vinegar and they came out spotless and shiny on the inside before I treated them with POR 15. Radiators can be flushed with the stuff and all the rust particles will be flushed out only problem is it is so good that it is a bit like taking your car to the blasters. If there are any holes which were clogged up with silt or rust it will expose them but I say it's better to know than not.

[paddyx350]

Ok thanks Rob

[paddyx350]

Filled up the cylinders with the vinegar last night, didn't have much to put in nos 1 & 2 as my vinegar supplies were low by the that time.
Had a peek down into the cylinders this morning and it's all gone.
The level on the dipstick is up over the mark and there's a very vinegary, watery mixture in there.
So more vinegar or go for the diesel now?
I'll definitely have to change the oil before starting it, in fact I'd be wary about even turning it over on the starter in case the vinegary mixture was pumped around the engine.

[paddyx350]

I've just read that vinegar will damage aluminium and the head is aluminium alloy?
Strikes me I need to clean the vinegar off the head quickly?
I filled the cylinders bores right up as suggested and the level dropped quickly at the start so I'm assuming that some of the vinegar leaked out through open valves in the head?

[JCS]

Chris

You have taken on board a very interesting, but time consuming and expensive project. I detect from your comments that you have a few reservations and like most enthusiasts need to keep a close eye on the costs.

Can I comment on the financial issue first?

It appears that the car has failings in every segment and all too often these rebuilds come to a halt due to time and money constraints, or even as we see today virus issues. It makes sense to prepare for the worst case and if no issues develop no harm is done.

It seems to me that you are going first into attack on the body work and in my opinion that is wrong and financially could be fatal. Body work is expensive in time and effort, slow to show results and when you have finished, at best you have a good body shell. If the project fails a body shell can be hard to sell.

If on the other hand you put effort into rebuilding the engine, brakes, front /rear sub frames and final drive then in the extreme case they would be very saleable.

At a later date it may be that you are fortunate enough to come across a better body shell, and maybe with luck ready trimmed. From time to time cars are stripped of their main components and the owner is often only too pleased to get rid of the body shell.
As this car has major issues in every quarter I think the approach should be very different from a rebuild that is not so intensive. Think what you might have tangible in say 3 to 4 years if you abort the project.

Meantime with over 50 year’s world wide experience in the automotive world behind me, I would say stop trying to run that engine before even more damage takes place.

You have already stated that the engine “starts fine but has developed a miss fire since I took delivery”.

Great! Now what if that miss fire is a result of a valve sticking, quite common on XK engines? I presume you can imagine that scenario. The cylinder bores and ring belt will already be showing signs of distress, and if it survives for long it will soon be down to less than 100 miles per pint. It would seem obvious that the engine has been stood for some time, so much so, that it is wishful thinking to believe it is going to drive far without some rebuild work.

Running the engine up at the moment will only blunt the piston ring edges, score pistons, collect some corrosion off the bores and hopefully not break any rings. Such running will potentially cause problems and risk breakages that may prevent a future easy engine rebuild. Save what you have to rebuild without components getting damaged, currently you have what is needed……it runs……any more is data that will alter.

Your biggest problem will be salvaging the cylinder bores. If it is original the engine should have no cylinder liners to complicate matters.

[paddyx350]

JCS,

Thank you for taking the time to pass on the benefit of your experience.
Of course you are right.. this car needs a lot of attention.
I envisaged that it would take a number if years and some money to do this when I decided to take it on.. and I am aware that I don't possess the experience or the whole range of skills necessary. My pockets are also not bottomless by any means although I do have a budget that I'll have to stick to.
I may end up as others have and being defeated by the enormous task that this project represents. My auto experience only runs to carrying out maintenance and elements of refurbishment to my xjs and xjr over the last 15 years.
But I have taken on quite a few things over the last 40 years which are similar to the S type in the challenges that they presented. These have included refurbishing properties, starting businesses and lots of other things.
So I have the space and time to have a go and I'll do that and see how it goes.

I thought the plan of dismantling and stripping the shell first was a good one to get an accurate idea of what I actually have under all the confusion of decades of repairs.

The objective of the compression tests on the engine and the advice given by 'cass' was to establish whether there was life in the old dog yet and whether it was going to be necessary to conduct a full rebuild. The engine seems to have very healthy oil pressure.
I take you're point about the dangers of causing damage to the engine but I think it would be useful to know if it does have decent compression.

So thanks again for your advice and I hope that with a bit of help from the great and knowledgeable members of this forum I can make some progress with this car.