Hello all,

I'm currently rebuilding my 1999 XJR's AJ27 engine and am trying to assess the condition of the cylinder bores. (roundness, taper, diameter etc.)
I'm in the process of measuring my cylinder bores and piston heads, but can't find the specifications from jaguar regarding the allowable clearances between the bore and piston.

I've searched high and low. If someone can share what I'm looking for I'll be eternally grateful.

 

can't help on that front, but wouldn't your 99 have an AJ26 with nikasil?

 

Hi Quadcammer,

Your are right that the blocks date (July 1999) would suggest Nikasil. But the cylinder bores are magnetic? So I had convinced myself that meant steel liners.

What are your thoughts?

 

I'm still new toJags, but if you find the engine serial number it'll tell you for sure. I don't know if the bore is different between an AJ26 or AJ27, but its best to be sure which engine you have,

Older engines I beleive the sn is near the thermostat housing, newer engines its on the lower left side of the block.

 

The engine number is 9907160244. So you're correct that this means it would have been manufactured with Nikasil liners. Is there a way to check if they have been replaced during the blocks life?
If it does still have Nikasil liners I would probably get them replaced with steel ones. So I'll still need the bore diameter tolerances.

 

The Nikasil treatment is directly to the aluminium casting of the block, therefore there are no liners in the Nikasil treated blocks.

If the engine needs to be bored due to excessive wear, the Nikasil treatment will be lost.

Why is the engine being repaired? Was there an overheating event?

 

Hi NBCat, good to know.
The engine showed significantly low compression in 4 of the 8 cylinders. (it also needed to come out anyway to access some welding that needs doing). Whilst it's been out I've replaced the valves and gapped them. Timing is all good with upgraded tensioners. So bores are the last box to tick to ensure compression is food once back in the car.

I'll find out if the wear is excessive once I've measured the bores (hopefully this week). If they are nikasil but within Jaguar specified tolerances, is it still best practice to bore out and add steel liners?

(not sure how I'll tell if wear is excessive without the bore tolerances )

 

Here is a link to the X200 Workshop Manual, which you may find helpful:

https://www.dropbox.com/s/jp6343385h...e_FSM.pdf?dl=0

Here is a link to the Engine Repair Course that has many of the specifications:

https://www.dropbox.com/s/vqpy3bbjzd...e_168.pdf?dl=0

Pay particular attention to the instructions for correctly timing the camshafts as many have incorrectly set the cams to TDC whilst installing the primary timing chain assemblies.

 

Sorry, I meant to send you the X308 Workshop Manual:

https://www.dropbox.com/s/9aid15mx5t..._1998.pdf?dl=0

 

If the cylinder bores are out of round, it may be best to obtain another cylinder block from a breaker's yard, or a later block already having the steel cylinder bore liners.

 

DJB, can you enlighten us as to what happened to get you to this point? Bought it broken, overheated it or??

Also, what’s the status of the car at this point? Is the engine out of the car and torn down or are you just gathering information at this point?

 

A little history on the Nik engines, high sulphur fuel was cryptonite to the lining. It accounted for thousands of engine failures for BMW & Jaguar.
Jaguar replaced a lot of engines under warranty, these have a green tag to show block replacement.
As you have cylinder heads off, you can check the state of the lining of each bore, I've found very small but obvious places at the top of each bore where the lining was gone/compromised and this is where the compression goes...scrap block at this point. A steel liner short motor (as heads are rebuilt) would be the more cost effective solution?

Looking for wear on a nik block? a good one doesn't, that's the whole point of this lining - if I had a choice (in a world without sulphur added fuel) between steel liner and nik coating, it'd be the nik coating because it doesn't wear and the engine package is a lot lighter. Porsche 917 engines used it! (Along with beryllium con rods).

Have you torqued the crank/bedplate down yet?
How did you install the con rods onto the crank? (re:dummie crank caps?)
I ask this so you can turn the engine and inspect the bore tops....

 

@NBCat Thanks for the documents. I didn't have the x200 one. It came dangerously close to being useful. They just managed to stop short of having the numbers I need

@Sean B Regarding the bore condition. The only chip to the coating is shown in the first image below. Other than that there is a slight lip where the piston rings reach top stroke (also seen in the photo). As, no matter how little, everything wears eventually. Other than that they are in very good condition (pending measuring).


@Addicted2boost Here's the story then

It's a 1999 XJR X308 with 120K miles. I've owned it for 2.5 years and it's been off the road for the last 10 Months. Ran fine before I took it apart.
It's last MoT included advisories for structural rust on all 4 corners. So I took it off the road to get it all welded up.
I don't do things in half so in order to do a proper job the engine needed to come out to get access to do the welding/ assess what needed welding.
I then made the classic mistake of saying "whilst I'm here" lets check the engines health since it's coming out.
The pressures read as follows:

According to the "Engine repair Coarse" Doc. they should be about 180PSI (it's worth mentioning the car ran fine with plenty of power! unbelievable)

As I mentioned above I have stripped, cleaned and reassembled the heads with new exhaust valves. (The below image shows the old ones!)
Between that and 75% of the valve gaps being out it's no surprise I had low compression.


Currently:
The engine is out the car and 100% stripped and cleaned. (see next image)
It will receive new piston rings and big end bearings. The crank and main bearings are in excellent condition and so will be reused,
I can't find grades stamped onto the pistons but measuring will determine that. All the bores are stamped as grade 2. Not that that matters after 120K miles of wear.
Engine serial number: 9907160244



Which brings me to the topic of this thread. The condition of the bores.
I think it's safe to say they're Nikasil based on inspection and the serial number (I guess the Nikasil coating must be magnetic, because my bores are!)

So the situations:
1. The Nikasil bores are within tolerance.
A. I could sling it back together as is. It's done 120K maybe it'll do another 120K?
B. Bore it out and put Steel liners in it. £2k but I'll I'll know it's the bees knees
C. Swap it for a steel lined block. £800 and will probably need the liners replacing anyway

2. The Nikasil liners are bad news, out of spec, damaged etc. etc.
A. Bore it out and put Steel liners in it. £2k but I'll I'll know it's the bees knees
B. Swap it for a steel lined block. £800 and will probably need the liners replacing anyway. (Could bore them out but oversized piston are impossible to find)

The pessimist in me says 2.A. is most likely. But I'm already spending more on this restoration than the car is worth (financially) and an additional 2K makes me question my priorities

But, the one thing I need for all of the above scenarios, is the bore and piston tolerances and clearances. I'll mention them in every post incase a passer by has the numbers I need

 

Hindsight being 20/20 I should have done a blow by test whilst it was still running but. There you go

 

In addition to my lengthy post just above, there is hope for the Nikasil liners being in good condition. The below image is looking up through a cylinder bore from the sub side of the block.

As you can see there are light grey areas at the top and bottom of the cylinder where the piston rings don't travel. The bottom (A.) has no notch at all to the touch. The top (C.) has a slight lip that can be felt but not catch with your finger nail.
But most interesting is the healthy amount of cross hatching still on the main running surface (B.). This surely means the wear is absolutely minimal. And all cylinders show no scrapes or gouges Apart from the small chip show in my above post.
If the bore measurements come within tolerance (what ever that may be) I would hope a new set of piston rings would be enough to get good compression. My only reservation would be about that chip. and if it's the start of a bigger problem.

 

Bore 86mm stroke 86mm for 4 litre. A 'Square' motor in that the bore and stroke are the same, Ferrari really like the square engine design, that's why all their 12's have 'that' sound since the 50's, apart from the flat ones!
I can't believe you bought valves instead of shims, a brass wire wheel decokes them in seconds back up to factory finish, got bags of them here, and shims.

Options, AJ4.0,4.2,4.4,4.7 it's how much you want to get involved. From the liner chip that block's done.
You can find whole cars for 800 in the UK now, so don't be stuck on engine only, look at cars too if you've space that is. MOT failure rot boxes but with serviced strong engines are now getting crushed....

Why hung up on mileage, I've untouched 300,000 R & 3,000 rebuilt by me R engines and both don't use any oil, quiet and matched in performance. Both AJ27S spec.

 

Looking at your picture, it appears that you have liners in the block. May just be an "optical illusion" - is the circular line pointed at by the red line not a boundary between the block and the liner insert?


Otherwise, Nikasil is magnetic but the magnet will stick to it fairly lightly and rather strongly to a steel liner.

I do not know where I found it but the info on bore diameters I have is:

Example - *21222122* - Cylinder Bore and Piston
The cylinder bore grades read from LEFT to RIGHT as follows:
Bank 2 - Cylinder 1, Bank 2 - Cylinder 2, Bank 2 - Cylinder 3, Bank 2 - Cylinder 4, Bank 1 - Cylinder 4,
Bank 1 - Cylinder 3, Bank 1 - Cylinder 2, Bank 1 - Cylinder 1. (Note, in earlier publications Bank 1 was
described as A-Bank and Bank 2 as B-Bank)
Grade 1 Bore = 85,990 to 86,000 mm.
Grade 2 Bore = 86,000 to 86,010 mm.
Grade 3 Bore = 86,010 to 86,020 mm.

 

This is the engine number of my Nikasil 1999 AJ26 SC engine (Daimler Super V8):


Is your engine number at the same location?

 

Hmmmm.... I hope I never get to the point where I can take similar pictures
on the Duchess. These photos really show up nice in the forum and I am
certain many will find them informative, Nice job guys!

 

Hi @M. Stojanovic The numbers are in the same place on mine yes.
And I think it's just an illusion. Even in person it's very hard to tell though. And they're as you say only lightly magnetic.

I've found the Below chunk of info in Jaguars "Engine repair course" Doc. BUT! These numbers cannot be both for Piston and Cylinder as the label suggest.
Otherwise you could have a Grade 2 piston that's bigger than a Grade 2 Bore!

@M. Stojanovic Your numbers for Bore Tolerances are attractively close to working with the above numbers. By only allow at most 0.027mm clearance and at least 0.003mm!
Which seems... rather tight, to put it lightly. especially as that clearance across a diameter. So 0.0015 on each side. I also wish you knew where your numbers were from
Thank you none the less though.

And so the quest continues