Hello,

are the heads in 4.2 N/A and 4.2 Supercharged engines the same / interchangeable? I also wonder if the camshafts are the same and differ only in the gears due to the fact that N/A have variable valve timing?

 

They're not the same.

You can just look up their parts online and see from there.

What are you wanting to do?

 

I suspect valve seals - but the fact that I will not find anyone in my vicinity to whom I would entrust this engine, I thought that I would buy the heads (because they are at a good price from 4.2 N/A) and make them on the side. If necessary, I will replace it :-). As of today, I can only buy one from STR, so I thought about a set from N/A because they are more easily available.

 

Valve seals will give you smoke at start up and at idle with the throttle closed.

Melllow

 

Yes, I know more or less typical symptoms, but I literally have smoke for 1-2 seconds only when starting the engine. Nothing at idle speed or while driving, with the gas pedal in the floor. Of course, the engine uses oil a lot because it can drink 1 liter for 1.5 - 2k km. Therefore, due to the fact that the replacement of seals involves the removal of the heads, I try to prepare for it earlier at a low cost.

 

Prior to doing any further repairs, a compression and leak tests would be a good place to start to determine the cause of the oil consumption. This will also be indicated on the spark plugs as oil deposits can form around the electrodes.

How many kilometres/miles are on the vehicle?

Are there any DTCs stored?

Does the engine leak oil?

 

That is quite high oil consumption.
My 120k mile STR does not need oil between annual oil changes, but I only do about 3k to 4k a year these days so that is not saying much!!

Mellow

 

The engine is dry as a pepper - I hate leaks and I'm sick when I notice something . The mileage is about 220k km, so I realize that it may be a bit worn out.
There are no errors - I check it often and remove defects on an ongoing basis.

I've had it for 2 years and I don't know how it was serviced before - judging by what I already did with it and I had to do it rather not very well. I've already packed a lot of money into it and it's not profitable for me not to finish it. The engine absorbs a lot of oil, basically without a trace, except for these puffs during firing. Unfortunately, as you know, a side effect of burning oil is carbon deposit and it is not healthy for the engine, so I think ahead over the engine.
In fact, it is worth doing an oil test to exclude the bottom of the engine. I took out the spark plugs at the beginning of the year and I do not remember them being sooty - rather all of them had the color of coffee with milk.

 

Btw
jaguar did do the STR v8 4.2 with VVT

 

Yes, later on. With various changes (e.g. to the PCM).

 

you can widen your search .
these heads are also fitted to Some 4.2 XKR's and some of the XJR's . non vvt variants .

it would pay to look inside the supercharger by lifting the charge cooler manifold .
or remove the throttle body .
and check for oil .

my 03 STR used to blow by oil from the PCV . Actually still does ,
i just added a catch can . and it's has stopped the start up smoke i used to witness .

 

I have an oil catch tank installed and the output pipe is still wet with oil. I already looked at the supercharcher last year because I took it off. The supercharger itself is dry, but the intercooler / intake manifold is stuck in oil, so I installed an oil catch tank. However, despite this, it is rather unlikely that almost a liter of oil per 1000 km was sucked through the PCV and catch tank? From time to time I pour literally a few ml of oil from the catch tank itself - either it doesn't work properly or there is such pressure that the oil still seeps into the throttle. Since most of the oil is released anyway, I wonder if I should throw this crap out.

 

So I did a compression measurement today and it looks like this:
Passenger side / Vehicle front:
1 - 12bar
2 - 13.5bar
3 - 13bar
4 - 12.5bar
Driver Side (LHD) / Vehicle Front:
5 - 11.1bar
6 - 12.4bar
7 - 12.6bar
8 - 11.8bar

I don't know if these are good results for an 18-year-old engine, but to be sure, I did an oil test on two cylinders and on 1 - 13.2 bar and on 5 - 14.2 bar. Adding a little oil is supposed to show whether the top or the bottom of the engine, but for me it is not entirely clear because it is known that the result will be better because I reduce the capacity of the combustion chamber. However, if a valve was leaky, it would not blow out 13bar because there would be a hole in the head ?? Interestingly, the spark plugs look quite good, but on the two where I have the highest compression, there is a thick, very hard coating on the electrode. Photos at the link. What do you think about it ? Let me remind you that this ******* already burns 1L of oil per 1000km and does not smoke like a lawn mower.

https://drive.google.com/drive/folde...Rt?usp=sharing

 

The compression numbers seem okay. Spark plugs labelled 2 and 3 in the photos show definite evidence of oil fouling.

 

Ok thanks for the answer - that would confirm other opinions I got and that valve seals wear is more likely. The engine is years old and I guess no one has looked there before, which does not change the fact that the heads have to leave the engine anyway and they need to be serviced.

 

I don't remember if the LH head can be removed with the engine in situ.

You may be able to replace the valve seals by removing the camshafts and using compressed air through the spark plug hole to pressurise the cylinder and keep the valves closed.

 

Ok, but since the timing chains need to be removed anyway, I'll do a few things by the way. I am thinking about a complete timing, but the slides have already been replaced with the corrected ones, so I do not know whether to push for additional costs. I would like to remove the heads anyway because I will take them to a specialist workshop to check them, replace the seals and adjust the valves.

 

If your engine has been properly maintained, removing the heads certainly would incur a potentially unnecessary expense. To replace the value stem seals in situ , the camshafts are going to have to come off anyway and checking the valve clearances is a normal part of completing the repair...

 

If it had been, I wouldn't have to do it now - I take care of it, but the previous 16 years are unknown to me when it comes to its servicing. One thing to note - removing the camshafts means removing the chains, which probably requires disassembling the entire timing, because I will probably not get to the tensioners from the top. You can't even set the timing without removing the front covers - I think so. In addition, the heads are at such an angle that doing it in situ is very inconvenient if impossible. The valve clearances will still be adjusted and you are guaranteed back pain and headache if something falls into it. I will take the heads off to a specialist and only a few gaskets plus new bolts and peace of mind for years.

 

It may be far easier to remove the engine from the vehicle so all seals and gaskets can be renewed. I have found it to be easier to remove the gearbox first and then the engine.

Yes, the timing chains, tensioners and guides need to be removed in order to remove the inlet camshafts. It would certainly be false economy to not renew the timing chain components when the parts are already disassembled.

Having the alternator and starter motor serviced by an automotive electrical specialist whilst they're removed is another good practice.