Hi All,

I've rather unfortunately started hearing the noise of a loud knock, presumably #1 con-rod. Engine was a little noisy last week, so over the weekend I pulled the belts and as soon as the serpentine belt came off, the noise disappeared. Seemed likely the belt or pulley as the noise was only at idle and disappeared completely under load. Then on my way to work it sounded like a bucket of rocks in the crankcase. Not an ideal situation. Issue isn't the tensioners as they were replaced by the dealer just a few thousand miles before I bought the car and looked pristine when I replaced the cam cover seals last summer.

I'm not seeing many options for used XJR or XKR engines, and even though I've never done it, would certainly be open to a complete rebuild. I'm assuming the crank is junk, and I'd read in a couple different posts here that the block and crank are the same between the NA and supercharged engines. So if that's true (and please shout it out if it isn't!), what are the major internal differences between the NA and SC engines? Obviously the SC has the Eaton huffer, different thermostat housing, different intakes, and I'm assuming different intake cams (no VVT), but is there anything else different internally? Can I buy a complete XJ8 engine with the intention of rebuilding that, swapping the necessary components, and dropping it into my car once complete? Am I better off with picking up a crank, bearings and a couple rods and rebuilding the bottom end?

Whatever the decision is, I'm going to document it pretty thoroughly as it may be useful to others. I used to be anxious about working on my Jags, but after paying a shop ridiculous money to swap out a blown pumpkin on another XJR, I've taken on pretty much everything to include cam swaps my XJ8L. I'm trying to get as much detail about the differences between the NA and SC engines as I don't want this process to turn out like a Top Gear project - ambitious but rubbish.

 

Car-part.com

 

You sure that "bucket of rocks" sound isn't detonation? I'd bet there's a lot more of it going undiagnosed given the carboned up pistons/combustion chambers and lowered octane levels from the stock crankcase breathing.
Just sayin'...

 

Will pull the #1 coil pack and plug tonight and do the dowel rod test, but it sounds exactly the same as when the bottom end in my '07 went out a few years ago. There was a lot of play in one of the bearings on the #1 rod when that happened, much to my dismay. The car also threw on the low oil pressure light just as I was pulling it in the garage - oil level was nearly full.

 

In your first post you said you took a drive belt off and the noise immediately went away. Did you find and repair the cause of that belt driven noise before condemning the engine??

Might be worth a revisit?

Also, if you have a difficult time finding a 4.0, maybe do a 4.2 but, you’ll want to swap your 4.0 heads onto the 4.2.

 

Correct, it was making noise that was only there at idle and disappeared under load, suggesting one of the drive belts. After isolating the noise to the serpentine belt, I ordered one. The engine is now making noise with all belts removed, the exact noise my 4.2 made when the bottom end failed.

Interesting you mention using a 4.2, is the block and crank the same as the 4.0?

 

4.0
Bore: 86mm
Stroke: 86mm

4.2
Bore: 86mm
Stroke: 90.3mm

The 4.2 crank and rods will be different.
To the best of my knowledge, the blocks are pretty much the same.

Whatever engine you go with, (if it’s actually bad) if your engine has a factory engine oil cooler, your upper oil pan will have the 2 holes on the front of the engine. The replacement engine may or may not have a factory engine oil cooler provision. Just an FYI. I do not know if the upper oil pan on a 4.2 will have the crank sensor hole IN THE EXACT SAME SPOT AS A 4.0!!

 

you can use a 33/34/36 short block. to fit the 4.0 intercooler manifold you need carefully drill a couple bolt holes in the 4.2 heads and you may still need a spacer gasket for the supercharger outlet. or use the entire manifold and fuel rail from the 03-09 XKR. or just use 4.0 heads


if it didn’t come out of an 03-06 XKR, you need the upper oil pan from the AJ27S. the dew98 cars have a totally different pan. seal it with ta-31 unless you want to do the job again

 

Dowel test failed big time, lots of movement in #1 rod as suspected.

 

Well that’s a bummer! I did forget to mention that the naturally aspirated and the supercharged engines have much different compression ratios. I don’t have those numbers though. I wonder if they’re the same between the 4.0 vs 4.2 NA and SC engines...

Xalty, do you know how to plumb the 4.2 top feed injectors that’s originally a returnless system to a 4.0 return type system?

Also, because the 4.0 has side feed injectors and the 4.2 has top feed injectors, do you know if the 4.0 ECM can drive the 4.2 injectors? I know at minimum the fuel injector electrical connectors will have to be replaced but I don’t know the ohms difference (if any?) between the two are.

Lastly, do you know if the 4.2 heads flow better than the 4.0 heads? Do you know why the intake splitters on the 4.2 is much more pronounced than the 4.0?

 

NA is like 10.5 SC is 9 to 1 on both

the entire setup of the 4.2 XKR works you just need to repin the large connector. the rail still has holes for the original feed and return lines. the only problem is XKR engines are expensive

count iblis has a bunch of posts on the differences between 20 series and 30 series engines

 

Well, I've come to the conclusion that I'll rebuild my engine rather than swapping an unknown engine. After seeing some of the completely trashed engines that I had found locally, I'd rather spend the time doing this right rather than settling for the unknown. I don't see the value in putting good money into an unknown engine for tensioners, seals and other common issues. This way, I can upgrade to the morse chains and pulleys that they had on the later engines. The only thing that I'm a little apprehensive of is the bearing tolerances on the crank, mains and the big end of the rod. I'm curious if the crank is salvageable, or if I'm better off spending a few hundred on eBay.

While I'm in there, does it make sense to bother replacing rings or are they known to last quite a long time on these engines? I have memories of swapping valve seats on an old car because the engine was a smoker, just to find that the rings were worn (that engine had over 170k). I would surmise that it's worth checking tolerances on all main bearings since I'll be in there. After some reading on the 168 engine repair guide, is it safe to say that the bottom end specs are the same for the AJ27 as the AJ26? For those of you whom have opened up the bottom end before, where can I expect to see markings and color codes for bearings, will it be stamped inside the block somewhere or on the bed plate? Will start putting together a list of what I know now is needed (just got the SNG Barratt guide!) and getting parts ordered.

I appreciate the wealth of knowledge thus far from everyone, it is certainly helping to guide me through some decision making!

 

early engines have the production date on water pump crossover and the important stuff to the block heater port/drain plug, driver’s side. yours will have everything next to plug

 

In case you did not check it out yet (ignore if you have....), there is good info in the "Brand review > Jaguar engines and transmissions" sub-forum

e.g. this post on swapping a 4.0 block with a 4.2
https://www.jaguarforums.com/forum/j...k-4-2-a-23763/

 

@xalty - That's one scary looking con rod failure, hope that wasn't your engine!

• Decision has been made to overhaul as long as the block itself is not damaged. If it is, then I'll make a table out of this one and source another one
• Good precision measurement tools procured (Mitutoyo for measurement to .0001", CDI for the crank bolt)
• Plan to replace literally all perishables during rebuild (hoses, tubes, seals, etc.)

The only question that I have, and more than likely for someone that has done a successful rebuild in the past, how the heck do I determine which bearing is appropriate for the block and bed plate? With the bore gauge and micrometer that I have, it will should be easy to effectively measure each bearing journal and bore.

I've printed over 500 pages of the student guides posted by several users like @motorcarman on here, as well as a 294 page version found elsewhere online. I'm looking specifically at page 3-10 from the August 2003 version - how do I differentiate upper and lower bearings or are they marked with paint dots as blue/ green or blue/ blue? I've not yet opened up my engine and realize it has to be done before I can measure the crank to see if it's destroyed (likely) or if I can salvage it. I've been very apprehensive of rebuilding simply because I didn't have the tools to effectively measure, but now that I do the only thing that I'm apprehensive of is, how do I determine which bearing goes where? I'm assuming a blue/green combo means that one bearing half is blue and the other is green, is this correct?

I'm finally ordering the engine hoist and spreader this week to pull the engine and strip it down. Side note, planning to order up some Simple Green Aircraft/ Precision cleaner, can anyone confirm if there will be negative implications to using this to clean the external surfaces on the block, sump, heads, etc.? I have methanol for cleaning mating surfaces to remove all gunk without damaging mating surfaces (use it for cleaning precision instruments prior to calibration, too) and can confirm that it won't be used for that.

I'm planning to start a new thread once the hoist arrives to fully document from start to finish the entire job, as well as all tools used. I've seen some posts where others have done similar work, though nothing that specifically calls out the time involved, tools required, parts costs, removal/ installation process, etc.

I appreciate all the support so far from everyone!

 

See the attached two documents. The info on what you have in the engine is stamped at the side of the block as shown on the drawing in the first document. This document also describes the meaning of each segment of the stamped codes and provides the graph for determining the selection of bearing colours. The second document (in two parts due to size) also contains info on bearing selection (from pdf page 46) and provides a lot of other useful info for engine rebuild.

You will find answers to your specific questions in these documents. Keep in mind that the grooved half of the main bearing always goes to the block side and the plain half goes to the bedplate.

 

ever consider a LS swap? with money you are going to spend the a replacement of another old AJ27, why not swaping to a LS3?

 

Zero interest in an LS in my XJR.

 

Not to mention that it would cost thousands more.

 

Yeah, if you went with a different power plant, the amount of money and fabrication needed would be huge even if you did most of it yourself. The entire rear end would have to be a Ford 9” (IMO) to accommodate such foolish HP numbers. Just thinking about everything needed to be done is giving me a headache. I would be happy with 450 to the wheels if the diff wasn’t so prone to breakage. Fortunately I’ve got a complete rear end ready to install with the sway bar.