So I am currently pretty close to buying an '85 XJS in very good condition with one minor problem; it has a "knock" and needs a cylinder head to be replaced, due to a dropped valve seat.

I have seen the car in person, heard the sound, and been assured by the seller that new cylinder heads are included and the fix is simple enough. He also will throw in some sort of custom tool he picked up for removing the heads.

The car won't be my daily driver (I am a student and don't really need to drive anywhere) and I have the time to work on it as well as a mechanically-inclined friend who is willing to help me both with his time and his tools.

My question is: is this fix feasible for me? I have little experience with cars. I will take my time and learn the engine through the shop manual and online resources. I have heard many competing voices telling me either yes or no that I can do this; and people have very different opinions of how difficult the operation is. Any other help or advice would be GREATLY appreciated.

 

How much are you paying for this Car?

If its not dirt cheap it may be better, to look around for something else.

Always buy the Best one that you can afford, one that is already running and doesn't have any problems.

Although I haven't seen it, that kind of mechanical problem would make me want to give that car a miss.

 

"Fix is simple enough" Haha!


Do you want a car or a project? I hope this car is free because the cost to repair it will likely be a very significant portion of its value in the end. A v12 Jag isn't a good place for a novice mechanic to start. You don't know what you don't know. This reminds me of my 19 year old neighbor who decided to build a motor cycle from scratch. All sorts of trials and tribulations along the way and it never got done, ended up as scrap. Along the way he practiced his welding skills, eventually got a steady job and bought a Honda Shadow. Sometime the journey is more important than the destination so ask yourself, is it the journey or destination in this case?
Maybe you'll succeed or fail, who knows.... Chances are you'll learn some good life's lessons along the way and those are priceless and perhaps a running car. Touch wood!

 

Well I am buying the car because I want to drive it (obviously) but like I said; I'm a student and I don't need to drive it anywhere. I may not even bring it to campus with me; may just leave it at my parents house for when I come home on break.

It's pretty cheap but best of all the interior and exterior are in great shape, and the mechanics are as well barring the knock. The owner was meticulous and replaced everything from AC to transmission to new seats; keeping the thing in a garage and giving it routine maintenance.

I'm mainly just wondering if the maintenance will go above and beyond swapping out a part. Supposedly I have everything I need; is there something I am missing? I suppose it makes sense that it will end up costing a lot, but I was hoping that to get it running would not be that big of a deal.

 

In all seriousness an XJS around my area with a dropped valve seat is a "donor" car for taxes. The cost and trouble of the fix FAR exceeds the value of these cars and anyone who fixes there's knows its a labor of love only. I personally would never pay a nickle for an XJS with a dropped seat or knock....too many decent runners for a good price to fool with that.

 

That car dropped a valve seat because the engine was seriously overheated. You may replace the valve seat, but that motor will not seal properly ever again. Get the car for peanuts and put another V-12 in it.

 

I don't think it overheated. The seller told me about the day it happened. He had a buyer lined up for 5 grand while the car was running fine; he told the buyer they would go for a test drive and as soon as he started it it started making the knock. The motor still starts and turns over and the car can be moved; he just advised against it due to possible further damage it could cause.

 

The only way Jag V12s drop valve seats is the result of a serious overheating event. Don't believe the seller when he says it was never overheated. It was, the dropped valve seat proves it.

 

Is this really the case you think? I am very inclined to believe the seller. He is a nice older gentleman with no incentive to dump the vehicle other than apparently his wife wants it out of the garage. I met him in person; talked for about an hour or so, and he related the story exactly to me. It wasn't as if he was making excuses for the part. He was happy to show me the engine, hear it run, and point out the trouble areas and the source of the noise. Everything ran great with the exception of the noise. I can't see how it would have overheated in that situation.

 

The heads are aluminum and the seats are steel, constant heat cycling causes them to drop ie lots of heated runs and shut downs AND any overheating episode...nice, elderly gentleman with an XJS with a dropped seat and knocking...walk away. You wanted advice and we are trying to give it....move on is the basic advice. If your going to convince yourself it's a good deal then scoop it up, only the price the car is probably worth is " free" sorry to sound harsh but Jaguars and XJS's are kind of my thing and we are trying to be straight with you.

 

Well, I think I'm done here. Thanks for the replies.

To be honest, I didn't find much that was helpful. Not much technical data / experience was cited by any of the replies. If someone had attempted this operation before and had a bad experience that would be one thing; but to tell me that the car is scrap metal is simply insulting. I am going to talk to some mechanics, see how much a professional job would cost, and if that doesn't pan out I will work on it myself. Like I said, it's not for my driving use. It was going to be a fun vehicle I could work on, learn a few things, and maybe enjoy driving in the near future.

 

If it was just a matter of changing head why didnt the seller do it and charge much more for the car. He is selling the car and will say anything to get rid of it. The valve seat dropped because of overheating. So there is a problem with rad, fans , hoses etc.
with a dropped valve seat the valve will no close and the partially open valve may be making contact with piston. If that is the case you are in for a world of hurt and out of pocket lotsa cash. Then you have to rebuild it or replace engine with another v12 or v8 chevy. More cash.
If its a project you want you got it.

 

Come back in a few years, you'll be amazed how much these guys have learned.

 

Geez, talk about biting the hand that feeds you. Tell you what Gary; when the phone doesn't ring you'll know it's me.

 

Gary. Dont ask if you dont want to know. All these people are experienced Jag owners and to insult them like that is rude. They are trying to help YOU make a wise choice.

 

Gary, these are some of the problems you will doubtless encounter, which you obviously do not realise lie in wait, and this is by no means an exhaustive list of what you will find:

• To remove the heads in car is a very difficult job, not impossible, but I would never try it. The day you take removing the engine will be nothing, repeat nothing compared with the difficulty you will face if you do not
• Taking the induction off the car will definitely produce engine loom problems which will haunt you for ever until you replace it all. See the thread here started by Jagernaut: https://www.jaguarforums.com/forum/x...-spark-118292/
• Once the head is off, you will find, as it is an open deck design, that the head gasket is unlikely to seat properly without the liners being realigned to spec, which is a pistons out job requiring access from the sump, impossible engine in car..
• Adjusting tappets cannot be done after assembly. The tappets must be set and the tappet block bolted up to the head as a pre-assembly operation, requiring the camshaft to be removed at each setup if you get the shims wrong
• new valves and springs may be needed and these are not cheap.
• The timing chain main tensioner will almost certainly break when you try to release it and will need replacing which is an engine out, timing cover off operation, and the timing chain will need replacing almost certainly.

All of this is great fun for an XJS nutter like us here, all the guys are doing here is giving you the punchline, above is part, repeat part, of the joke. It is not a quick or easy job. I think you owe them an apology.


Greg

 

Average cost of doing one head by a mech around my area in the past was around $4500 and you never just do the one. The technical data you seek was given. Walk away. What you wanted to hear was "buy it" but that's not good advice. People here were trying to help. You seemingly wanted to hear good news and in this particular case there isn't any. I'm not into sugar coating things and apologize if you were offended.

 

Gary, these guys have probably forgotten more than you will ever learn about Jaguars if you don't take advice from the great pool of knowledge available to you here. You will end up with a car you either can't fix yourself,or afford to pay for the repairs and you will very quickly lose interest in it. And it will become "scrap metal".
It is simply an insult for you to ask for advice then say you got no help,there were at least 8 very helpful posts in less than 12 hours.

 

Gary, I've owned 6 V12 XJSs, a V12 XKE, and several V12 Jag sedans. These guys are right on target. These cars are a labor of love. I've rebuilt two Jag V12s. It is a serious undertaking. I won't say the guy is lying about a serious overheat. My E dropped a valve seat after 3 years of ownership, and although I NEVER had the car run hot, I do feel that years of heat cycling caused the problem.
This car most likely needs to be free, to maybe 500.00, no matter how nice it seems. Because you could spend 1-2K just doing a valve job, and another 1-2K might just get you a running driving car, with just the need of maintaining it.

 

And by all means, please download the FREE "Experience in a book" by Kirby Palm. You will find more than you ever dreamed, or even want to know about these cars.