AJ6 engine into a X300 car?
 

As some of you might have read in the timing chain interference engine thread, I have purchased a 1995 XJ6 VdP with a suspect motor.
I do not have the car back to Ohio yet but I have been thinking about how I will go about repairing the car so I can drive it.
I have several spare 4.0L AJ6 motors and I am wondering if there is any fundamental reason why a 4.0L AJ6 motor could not be installed in a X300 car.
I know the cam cover on the AJ6 does not have the mounts for the coil on plug modules but would the AJ16 cam cover fit onto the AJ6 cylinder head?
I also seem to recall that there might be a bolt pattern difference between the AJ6 exhaust manifolds and the AJ16 ones.
So the AJ16 exhaust manifolds might not bolt onto the AJ6 cylinder head.
If that is the case maybe I could use the AJ6 exhaust manifolds assuming the downpipe connections and locations are the same.

Anyone know any other gotchas that might bite me in the butt if I tried this?

The engine ECU for the AJ16 engine car and it's wiring is already set up for you . The engine ECU and the transmission ECU are inter wired as well as the rest of the car like the A/C , alternator , BPM ECU , security ECU , fuel pump control , and on and on so there is something that will stop you from success .

The AJ16 engine in a worse case scenario with your 525 buck Jag ( no offence intended but there's your personalized licence plate ) has the option of replacing the the D clip on the drive gear and replacing the valves from the donor engine in KC ( I'm going to use the head and experiment with valve throat opening or porting even though it may be warped out of machining limits / cheap ) makes the valves available with some valve lapping compound and replacing the stem seals if stressed to one side .

There is a reason the valve timing went off and maybe the the previous owner had a low competence level as he was tinkering with it like the previous with mine

There was a reason the timing chain looks intact and not bunched up and probably the D clip or other spline device went aaaaaaaaawinck

I'm not an expert in the field of Jaguars but I'm working with what I got . and that's not alot

Off the top of my head, engine management and various electrical connectors may be issues.

The AJ16 used the Lucas/Sagem/GEMS engine management system while the AJ6 used a Lucas system that if I recall correctly was licensed from Bosch. The electrical connectors on some of the sensors may be different. Also, the AJ6 has no camshaft position sensor (CMP) which the X300 ECM references at engine startup to identify cylinder 1 TDC within less than one full engine rotation. Without the CMP, the ECM defaults to the crankshaft position sensor (CKPS), which can take up to 30 seconds to identify cylinder 1 TDC so the ECM knows how to time the ignition.

The late '94 AJ6 camshaft covers may have the same screw positions as the AJ16 cover - if so, you might be able to use the AJ16 cover and on-plug-coils. A test fit should answer that question.

The '93/'94 XJ40s have the same higher output alternator with the wider pulley so their CKPS brackets are the same and you could just use the AJ16 CKPS on the AJ6, although I am not certain whether the reluctors/tone rings/timing rings on the harmonic damper have the same tooth pattern (they are different part numbers).

The coolant temperature senders that drive the IC temperature gauge are the same part, but the engine coolant temperature sensors (ECTS) that the ECM references are different part numbers (the electrical connectors are the same, though).

You could swap the AJ16 fuel injectors into the AJ6 - they're the same size and similar in performance to those on the '93/'94 engines. If I recall correctly, the inlet hose on the AJ16 fuel rail is different from the one on the AJ6, but you might be able to swap the AJ16 fuel rail onto the AJ6, possibly with some modification of the mounting points. The fuel pressure regulators are the same part.

The carbon canister setup and plumbing is different but you might be able to adapt the AJ16 setup to the AJ6.

The X300 and 1990 and later XJ40s used the same ZF 4HP24 transmission, but the part numbers are different for the late XJ40s and the X300s. I don't know if this has something to do with the transmission control module (TCM) interface, the bell housing mounting points, or some other difference.

I'm sure you will have lots of other challenges, but these are ones that come to mind.

Cheers,

Don

I was NOT talking about changing any of the X300 / AJ16 engine management. I am talking about the basic engine long block. From the top of the cylinder head, down to the bottom of the oil pan.
I would keep ALL of the AJ16 / X300 engine management, transmission and what not including the AJ16 intake. I think the only pieces I might have to use outside of the basic AJ6 long block might be the AJ6 exhaust manifolds.

The AJ6 is a 2 valve per cylinder ( if I recall ) and the AJ16 is 4 so the actual intake and exhaust flutes as they come together before exiting the head may have a different size and shape

The ignition distributor as the hole on the left front side in your pic was replaced by a finer resolution cam position sensor that helps the car start faster and the ignition timing is then controlled by the ECU

Alot of variables that can be off in the last steps of conversion like the different sensors physically fitting and " adjusting " to the ECU

Very interesting question. The most obvious difference is the AJ6 has a dizzy and the AJ16 has coil packs BUT, as far as I remember you should be able to plug the camshaft position sensor inside the dizzy hole and use coil packs if you can transfer camshaft cover from AJ16 to AJ6. Mounting holes are exactly the same from memory. I suspect you could even use coils with AJ6 camshaft cover but you'd need to somehow fabricate holes for coil bolts. Other than that the engines don't look that much different. When you start taking them apart you'll find the AJ16 has a slightly different crankshaft and con rods, and the heads are slightly different, as you know exhaust manifold from AJ16 are completely different and you'll need to use AJ6 ones but they will connect to the exhaust with no trouble at all. The AJ16 has a much better inlet manifold but I believe bolts will be in the same place. Fueling is almost exactly the same on both engines(5% increase on AJ16) so ECU and engine should handle everything with no problems at all and fuel rail should go in the exactly the same way on both engines.
If you get both engines side by side, this should be much easier to answer, I'd say main issue might be camshaft cover. Everything else is shared with the late 40, you might struggle with Ac compressor mount, both cars use different compressors and I'm not sure if X300 compressor will mount anywhere to AJ6.

AJ6 is a 4 valve head
 

Wrong! The AJ6 is also a 4 valve per cylinder engine just like the AJ16. You are perhaps thinking of the older XK engine that was used through 1987 in the US.

I think the only AJ6 engine with a cam cover that might work is from Engine (179542) onward. (1993/94?)

The earlier AJ6 has a cam cover with 7 fasteners. The later ones might be the same as the X300 bolt pattern??

Good luck with the search.

bob

I think sourcing an aj16 would be better and easier. If you have spare aj6's you could sell one to recoup the cost of the new used engine. There are several one fleabay and salvage sites that will ship to you.

I've checked my Haynes and holes are in different places so covers wont be interchangeable. This mean that AJ6 cover will have to be used as I suspect it will be much easier to somehow mount the coils to it than fabricate holes for the AJ16 cover so it fits AJ6 head. Coils don't really need much support to stay in place, unlike the cam cover which really needs to be be tightened properly or it will leak oil.

Well, the previous owner said the car was idling and then suddenly stopped running. He said that when he pulled the cam cover and turned the motor over with a socket on the crank, that the cams did not move.
I have to imagine that prior to that there was also some prolonged cranking of the motor on the starter while attempting to restart.
Since I still do not have any definite call on what would actually happen if the lower timing chain broke as far as valves impacting pistons or not, I don't know if the motor would be prevented from smoothly turning over on the start for full rotations or not.
When I looked at the car in the storage yard in NJ, the upper timing chains looked normal. He had the crank damper pulled from the motor and the cam sensor pulled out of what I always consider the "distributor" hole on the side of the block.
He also had the crank sensor bracket pulled from the front of the engine and the various tensioner parts pulled from the motor. As a result there was at least one open hole also visable in the front of the timing cover.
But I did not have a good light or anything I could use to peer down into either of the open holes and I am not really sure I could have seen anything anyway.

Yes, I do plan on diagnosing the problem but according to what I have found getting the lower timing cover off is quite a job.
I plan on first pulling the cylinder head since I want to see if there are any valve impact marks on the top of the pistons.
Then if that does not reveal the smoking gun my next step might be to start pulling the engine while leaving the transmission in the car.