Dear all, we are making restoration of XJS 5.3 1977.
Thanks for everybody who help us with previous issues.
Now the question about cylinder heads.
We send both to company specialized for restoring heads. They made pressure test, changed valve steams, seals, made valve clearance according jaguar books etc.
We received the heads few days ago. We observed erosion on cylinder head surfaces. The guys made repair said it is not a problem and we can mount the heads without worries. Please check the pictures and give your opinion.
Some of the erosions are 3-4 mm deep.
Best regards, Stan

 

Very risky to use thee heads as is. They've got some serious pitting should have been decked and checked with a head gasket to ensure a good seal.
What are the ridges on the exhaust valves? If they can be felt, then they will heat up and may cause preignition.

 

That's pretty severe corrosion. I'm very surprised a competent machine shop would have done anything to these heads without asking for further instructions. I wouldn't use them as they are, I'd either find a new set of heads or have the corrosion ground out and welded up, then machined to make a smooth surface.

I'm guessing this engine was either run with water as the coolant, or the antifreeze was never changed?

 

The heads are unuseable with 3 or 4mm deep faults in their surfaces and will fail very quickly, if not immediately. These are too deep to be machined off. Find new heads on UK Ebay etc, or maybe, just maybe, get them filled up by a really competent aluminium welder/head restorer and then they will have to be re-machined.
For examplz, these might be OK; but they need inspection before buying.
https://www.ebay.co.uk/itm/325515078...Bk9SR7D7oM7PYQ

 

Agreed. Not on any of my engines.

AND

I would also be VERY concerned about Internal corrosion. The stuff you cannot see.

 

Thanks for replies,
It will be very hard to find preHE heads.
Maybe HE heads will fit?
Any change of performance?
BR
Stan

 

HE heads will fit, better performance and MPG in road driving BUT you will need to chnage the pistons and the use the HE ignition and injection systems.

 

Stan 73,
Those heads are possibly O.K to use depending on what you plan to do with the car your engine is fitted to.
By the way, it always help to say where you are located. It can make a difference to replies from this forum.
I would put "engineer's blue" or similar on all the mating surfaces of the block. Then drop the head onto the block.
Pull the head up an take photos of the head surface. Let forum members give an opinion on the photos.
What you are looking for is that all the head surfaces that need to seal against the block are a good machined surface.
The most important surface is the firing ring around the cylinders. That is the most critical area.
The other surface is around the perimeter of the head which seals the coolant. That is not quite so critical since it is low pressure and you can always add a sealant on the head gasket in any area that is not 100%.
You also have to check those oil drain holes, you want to make sure they seal.

The corroded part of the head is mostly where it contacts the coolant. Looks bad but does not in itself mean the head must be scrapped.
There will be many V12 engines still running in cars with equally bad head corrosion because many owners do not bother to drain and replace coolant on a regular basis. You have just found that out with your engine.
If you plan to race the car, or want another 100,000km of 100% reliable trouble free driving, look for better heads.
However, many XJS drivers only use them on fine weekends ( like me ) and rarely use much power.

Below is one of the heads pulled off a 5.3L HE V12, maybe from 1984 car. After cleaning up the head with fine emery paper there was obvious damage on the firing rings of more than cylinder. It looked likely that too much of both heads would need skimming to clean it up. I scrapped the heads and bought brand new ones from SNG Barrat for a reasonable price. I am not sure you can find brand new pre HE heads.



V12 HE head

 

Dear all,

I would like to share our experience with cylinder head corrosion.
We found a company in Bulgaria which offered us
some Russian method for layering aluminum dust at corroded aluminum. The same method can be done at corroded iron cast. The result is impressive. The pictures attached. You can see fixed places are grayer than head’s aluminum.
The machine and bottle with special aluminum dust also attached. The machine using pressure.
this is not advertisement of Russian technology,
it is not possible to import anything from Russia nowdays. Just sharing experience.

BR Stan