Just as my love affair was peaking, the number 2 and 3 cylinders only show 40lbs pressure. All the rest 120-130lbs compression. Me thinks the head gasket is blown. And I baby her for just that reason! I'M the one who has to fix her, so I don't beat on her at all. (Too many "hers"?). This is a swapped-out engine by the PO from decades ago. It's SN#: 8L 40403 L. Does anyone know when the infamous "slotted" block SN's began? And might my engine fall into that category?

I'm trying to search this forum for all the good information on how to proceed with getting the head off, what to look for, etc. Trying to find all the links and PDFs and .DOCs of all you folks that have been through this before. I've rebuilt several engines before, and done lots of work on this XJ6C, so I'm not afraid to throw myself into the thick of it. I just don't want to make too many mistakes - and minimize the down time. And I would just love, love, love it if I didn't have to do a rebuild, but "just" a head gasket replacement.

Your Thoughts, links, files, parts needed, other things I should be thinking about, words of encouragement?

Many thanks, Bill

 

I've done head gaskets three times.

Removal can be a problem if you're in a hurry,

By far the easiest way to get the head off is to remove the studs. The worry is that a rust-weakened stud will break in the block.....which really complicates things. But, if you're reasonably confident that the cooling system has been cared for just pull the studs and be done with it. A possible downside is that, after the studs are removed, crud will fall into the holes. When you go to reinstall the studs this crud will prevent them from threading all the way home.

If that risk is unpalatable lifting the head off the studs is Ok, too. I say "lifting" but, really, I found it's easier to push the head off using a couple of small bottle jacks. The head is wider than the block which leaves a small ledge to push against. With a little cleverness and some wood blocks you can create a solid base for you jack. I can't remember the exact details but if I can do it, anyone can do it. I just kept adding pressure from the jacks (one on each side of the head) and after a couple days the head broke free. After that it was a matter of alternating the position of the jacks so as to push the head upwardly evenly.

Cheers
DD

 

Log shot a valve issue. Any better, probably not.

Diagnosis to confirm compression test. Add oil to the cylinder and retest? Better ?

Check the parts place for a combustion gas detector. Attaches to radiator filler cap.

In drastic cases, you can see air bubbles in the coolant with he engine running.

Agree, think out the process.

tools needed. Where to do the project. When best to start. Parts needed. Who will skim the head. Or a means to determine if this is necessary. time to lap the valves "while you are in there" !!! Replace the studs, possible. Where and how to clean up the head. /

 

 

Bill
Drain the coolant, remove cylinder head dome nuts now and start squirting liquid wrench, mouse milk …. "your favorite corrosion remover" around studs ever time you pass the car in the garage, yes... you will need the bottle jacks mentioned and shown in the pictures, if you don't remove studs first. Defiantly install new cylinder head studs... breaking one on removal is a joy, compared to breaking an old one when re-torqueing an overhauled cylinder head.
Rgds
David

 

The 8L blocks, like the 7L before them, suffered from cracking between the bores. So when you get the head off, check very carefully for these. The cylinder liners aren't there just because Jaguar thought it was better than the cast iron, but to cover two coolant passages machined in the block between each pair of bores, This means there is effectively a narrow bridge of cast iron between each bore that cracks over time. The thinwall liners don't crack, but are too narrow to keep the combustion pressures contained, especially as once cracked the cast iron sinks slightly. The cure is to fit lipped liners that meet each other and cover the cracks. Obviously this is an engine-out and complete strip down job. On my engine, I rebuilt it around an uncracked 7L block that I was very fortunate to find.

The slotted 8L blocks were introduced around 1982 I think, and was a quick spatchcock by Jaguar to eliminate the cracking. By this time the XK engine was on its last legs, as the aluminium AJ6 engine was to be used in the new XJ saloon, the XJ40. However this was delayed so the XK had to soldier-on until 1986 when the XJ40 was finally put on sale.

 

Some of you will remember this. We got the recond head back Saturday afternoon. Few beers and fitted the head and broke a stud.
Called Muz52 (member, Murray Scoble of Peninsula Jag Engine Centre) sunday morning, we picked up the recond shortblock 5pm Thursday and did a 12 hour day Friday and did a road test 4pm the same day. Saturday we went on a Jag run through the mountains for a shakedown and Sunday we did a track day with the Jaguar clubs sporting group coming in second overall for the day.

JUST REMEMBER WHY YOU ARE DOING THIS, IT'S A HOBBY.......ENJOY. If you dont have fun doing it give up and do puzzles or something.



At this point it became a very expensive wine rack for the night.

 

Good on ya, boys. Been there, done that - well, not the racing part anyway...

To Bill's initial question - As the visual aids prove it's a tedious but not difficult job and goes faster if you have assistance. I've done it several times (twice on the same car). Even got away with reusing the head studs a couple of times.

 

The YouTube channel "Living With A Classic" has some really good videos on the head gasket issue. I think his XJ is a 1975 S2.

 

I'm keeping this line, Clarke! You may see it again sometime.
(';')

 

Only if this interests you. I just removed a Jaguar 4.2 engine/trans from my 1985 Sovereign with 110K miles on it. Factory reman transmission included. The usual oil leaks, Tappets need adjustment. Does not overheat.
$200.00. Priced to sell.

Thank you.

Larry Louton
Venice, Florida.

 

I agree, get a good used engine and do (or have) all the work done while it's on an engine stand. Then when it's all shiny and beautiful swap it out for the broken one in the car. While the new one is being rebuilt you can drive your car as long as there are no major issues like oil and water mixing too much.

If I was going to keep the car forever like, I believe you are Bill, I'd want the whole engine gone through (like new gaskets throughout). So you can drive trouble free (and drip free) for the rest of your life.

Jeff

 

Thanks to watching those YouTube Videos I was able to get the head off by myself without donating any blood. You think the gap in the head gasket between 2 & 3 would create 40 lbs compression?? The good news is that there are NO cracks in the block. However the Upper Left Chain Guide's plastic (or whatever material) has removed itself from the metal plate. And I have to fish it out. I can see it so I think I can get it out. Anyone know what its function is in life? And.... can I replace it without having to pull the timing cover off? And what if I don't replace it. What harm might befall me.

I'm not compiling a list of parts I need and will order them from the best priced supply house. Always open for suggestions on any of the aforementioned. You guys and gals are the best!

And, YES I will own and maintain this car for the rest of my life. And yes, I enjoy working on it, once I'm past the "denial" stage and into the "acceptance" stage.


Gap between 2 & 3


Head Off


Part Number: C13616


Bill

 

Going out on a limb here, Bill, but it's just Possible you have found the reason for low compression there.
I have surmised in my time here, that this is not an unknown problem with these engines. I hope you get back on the road soon so you can DRIVE THE WHEELS OFF during the Season.
(';')

 

I had a non-slotted 4.2 from 1976 that had the almost invisible to see cracks between the bores. I decided to get a latter engine from 1983 (I think) and install that instead. It did have fuel injection but I turned it back to my original carbs. It did need some other modifications, but all the parts came from the original engine. I did need to change the carb needles and adjust the timing. I am very pleased with the result. I still have the old engine, but it has part of a broken tap in one of the stud holes. There does not seem to be any sinkage at the crack areas interestingly!

 

If the blocks OK and the Heads Ok"ish. I start to think it's a problem with the actual gasket design? With todays technology, surely the gasket company's could produce a gasket that does not fail? I understand - or believe I do, the silliness with the close bores, but if they are intact and all that fails is the gasket - I perhaps am missing something. Just a thought.

 

Can you give us a much closer shot of the top of the block, please.

 

Interesting. Did you use the EFI head, and if so, did you modify it in anyway? I have a "spare" Series 3 motor (I think) - has a "H" after the engine #, which I'm guessing designates "high compression". Hoping to use this engine to replace a seized Series I, a car I bought years ago whilst wearing rose coloured glasses!
Any tips appreciated.

 

I used the engine as it came with the head and block assembled! I will try to take a photograph or two over the week-end .Alec G.

 

Aye, Bill, as Fraser asks, a closer view of fhe block at the point that the gasket failed.

In two past critters, I had a similar gasket failure. The thick part around the big hole is known as the "fire ring". Intended to contain the force and heat of combustion. In my past some gasket brands were better than others in that respect.

A "low" spot at that point in the block or head invites this type of failure. And improper torque and torque sequence just might have something to do with it.

1. 55 Dodge pickup powered by the p Too much water in the sump!!! polyshere headed 272 V8. Ran on 8. But, lost coolant and OP went to 0 PSI!!!! Blown gasket.
It got a valve job and bearings and ran just fine.

2. 57 Ford pickup. Power by 312 CI Tbird sourced V8. Blew a head gasket. Same issue, between cylinders. This time, a visible low in the block at the point of failure !!!!!!

I used an old machinist "bodge". Tear down and build another engine not in the time or $ budget... Sharp punch. Hammered in a few dimples in the low area. Raised the level. Dressed off with a sharp file. Crossed four fingers and four toes. it worked... Back to the road. One fast truck...

Often wondered if a JB Weld would have held??? .