Head to Head (Cylinder)

[dennis]

Hi All,
After some months seeking knowledge and causes of my engine smoking when hot after acceleration I have decided to change the cylinder head with a like for like 3.4 engine I bought as a possible 'spare' when I used to own an XK120. I have had this 'spare' head checked and it has it has earned a 'very good' report from a very knowledge engineer friend of mine which as worked on past and present Jags. He did suggest I had it very lightly skimmed which I did. Unfortunately he now sufferers from age related problems and cannot take on changing the head for me, this is also the same for a second possible engineer friend taking on the work.
What I am really saying is after some trepidation I have decided to undertake this myself. I have ordered replacement head gaskets from SNG and armed with the Service Manual ready to go. I have been helped a great deal by the forum in the past and now ask for any advice you may know of that would help me.

[cass3958]

The only advice I would give at the moment is the hard part is often splitting the head off the block. Even though it is made of aluminium it is heavy and has to slide up over the studs. Some times there can be corrosion between the iron studs and the alloy head which causes the head to stick. The other problem is unless you lift the head evenly over the studs you can have it jam up as one end lifts and the other does not. When taking the head off it is more than a two man job and I would recommend lifting the head off the block using an engine hoist or crane. This way you can exert even pressure as you lift, it also allows you to lift without having to use crowbars between the head and block with might cause damage whilst lifting. I had my engine out on an engine stand and was able to lift the head off by myself using the engine crane method but there is no reason this method cannot be used whilst the engine is still in the car.

[dennis]

Cass,

Many thanks for your info and pictures of engine hoist, I have got a friend who had said he would lone me his hoist when I was ready.

Starting the work on the engine I have seen for the first time the very small wire breather on the transmission oil filler dip stick entry access.. It is difficult to say whether this is blocked or not, and I cannot see how the wire breather could be removed , could a blocked breather cause any problems, like engine smocking .
Ths is again
Dennis

[cass3958]

The Auto gearbox oil should not get hot enough to cause smoke and if it was then you would tell by checking the gearbox oil to see if it is still cherry red (good) or dark brown (bad). If it was dark brown you would smell a burnt smell in the oil. Reasons for burnt gearbox oil could be lack of oil in the gearbox or very worn parts like slipping bands but this would not cause any smoke.
Reasons for a smokey engine through the exhaust pipe could be worn piston rings. Damaged bore. Worn valve stems, guides and seals. Worn valves not seating correctly. Another simpler cause could be that the gauze on the front of the breather on the front of the chain cover is blocked. The crank case breathes through this gauze in to a pipe that runs to the air intake so the oily air can be reburnt and sent out of the exhaust. If the crank cannot breath then the gases with make their way up the bores into the combustion chamber and out of the exhaust causing smoke. Remove the coil and then the four 7/16 domed headed bolts and pull off the domed cover plate. Take the gauze out and give it a good clean in some old petrol or use a degreasing agent. Also clean out the filter in the Californian emission's pipe.
If the smoke is coming from under the bonnet generally speaking it is a cam cover gasket that has failed and a small amount of oil will be dripping down the side of the engine on to the exhaust. The gasket is made of cork and in time the go hard and start to leak. This where most XK engine oil leaks can be found. New gaskets solve the leaks.

[John Quilter]

And you can use Dowdy washers under the cam cover studs to prevent leaks at the studs.

[NigelW]

Hi Dennis, before pulling the head off try a compression test to see what the state of the engine is in, if you're getting smoke on on acceleration after over run then it indicates worn valve guides or at the best case the valve seals have hardened and loose. As Rob says excessive crankcase smoke/fumes might not be getting past the mesh filter on the breather, just remove the oil filller cap to see if anything is coming out, a blocked filter will cause excessive pressure building up in the crankcase and blowing any weak gasket points eg the cam cover gaskets - they are paper BTW.

You say you are thinking of using the head from a xk 140. I think you will find you will have problems hooking up the rev counter as the 140 uses an mechanical drive located on (I think) the exaust cam side. The S Type uses an electric generator on the inlet cam. It might be worth researching the cam profiles used on both heads.

I meet you a few of weeks ago at the Matching Green car show by the way, I had the green S Type, if you need any help with this I'm only 12 miles away on the Herts border, drop me a PM.

Nigel

[dennis]

It never rains just pours !
After removing the 'smoking' head but before replacing I together with my classic jaguar consultant decided to try to find the toot problem and started removing with a compressor the valves from the head one by one]. Arriving at nos 6, all was revealed I have heard of a dropped valve guide, I can now say I have seen one ! I have forgotten how to attach a picture, I wanted to show the dropped valve, what I have done is put it as an attachment file but I don't think this is the way to do it.
But moving on, replacement head fitted, engine starts , no leaks, drive it arround village green it's great ! problem solved.
Today I needed petrol so I drove it ti the petrol station, drives beautifully.
But wait I have a water leak, still plenty water in rad, can't see where problem is so promptly drives home. The water leak is coming from the ' hole drilled in ti the water pump casting which act as an air vent ' ( quote from the S Type Service Manual. it is a steady small stream.
Is this a worn water pump that needs replacing or is there something causing it or can it be repaired ? There doesn't seem to be much explanation in the manual.
Can any one help, is this a common problem ?

[cass3958]

Thought I would clean up and brighten up your photo for you so you can see the dropped valve guide more clearly. Interesting as I have never seen one before. Good to find a problem even if it is bad. There is nothing worse than stripping the engine down and not finding anything but still no wiser to what the problem was.

1 A Dropped valve guide.jpg (1.75 MiB) Viewed 552 times

To post a picture I think you have done it correctly. At the bottom of the page there is a TAB that says "Attachments". Click on this then on "Add file". You then navigate to where the photo is on your computer and click on it and it up loads. Once up loaded you can choose where it will go in the text generally where your cursor is or if you are adding several pictures you can choose the order in which they are shown.

[NigelW]

That valve guide looks familiar, the same thing happened to my engine. I can't remember now but I think I had the machine shop fit over size (outside diameter) guides, this was back in 1980. When I did the latest rebuild in 1998 I had new guides machined from solid bilit to get a good fit.