What differences are there in the 5.3 V12's other than the H.E. heads? Could an earlier 70's engine use the heads and intake off an 80's H.E.?

 

At minimum you'd need different pistons. That's about as far as my knowledge on the head-swapping goes.

Cheers
DD

 

As Doug says, you will need to replace the pistons to match the HE heads. Also don't forget that you will need to change the fuelling settings somehow as the HE has a higher compression ratio.

 

Jag changed the rear main seal from rope to lip seal in 1989 also. If you are after power the pre-HE heads are much better for this. All of the Jag racers used the flat heads. Due to the design of the HE combustion chamber the valve size is limited. The HE heads are limited to around 450hp.

There were also differences in fuel injection and ignition. My 1989 runs Marelli which is a full ECU controlled ignition system. Still uses a dissy and rotor to distribute the spark but no points has 2 igniters and coils. With the higher CR the older ignition system might not cope with the advance retard.

If it is power you are after I would be inclined to keep the flat heads. Then a number of options.

1. Bore and stroke the standard crank can be welded and offset ground for 78mm stroke and standard bore giving 6L capacity or you can bore up to 93mm with 78mm stroke giving 6.3L capacity.

2. Aftermarket ECU there are a few Megasquirt systems running around on Jag V12's all be it in different vehicles.

cheers W

 

Eventually I will be looking at the performance changes, but for now I'm just looking at what options I have.
Here is the scenario. I have an 83 H.E. convertible with 28,000 miles, in good condition, but doesn't run. It's been sitting in a garage for several years before being sold to a salvage yard because there was no title in the state it was being sold (in my state a title isn't needed if older than 10 years). I bought it cheap...really cheap for that reason.
Before I picked up the car, I checked the oil level. It was a quart or two low and had a couple drops of water on the stick. My first thought was it might be condensation, but could be head gaskets or even cracked block, hard to say. I drove home in a horrendous downpour, and the next day when I checked the oil, the level was full and more water on the stick. I wondered if maybe any water left in the system leaked down into the crankcase after moving the car around and on and off the trailer. The engine doesn't turn over, but I'm not yet sure if that is because the battery is weak or if it's seized. I wondered if it might also be hydrolocked if it was the head gasket.
Today, I was pulling the plugs to do a compression test and to check for water, and so far I've pulled 6 plugs from the front and they are clean and dry. However the oil level is now several inches above the full mark after a torrential downpour on Sunday.
The car hasn't moved, so I'm lead to believe water is somehow leaking around the hood and finding it's way into the engine.
Any suggestions as to where the most likely area water would find it's way in? I would think between the V, but as I'm pulling the plugs I don't see any puddles or any way it could enter?

 

Its highly unlikely the block is cracked these things are bulletproof. More than likely head gasket. If the HG is gone it is pretty likely you will have a dropped valve seat.

I guess there are 2 ways to go

1 remove the heads and survey the damage if not too bad, do what is necessary to get it running.

2 look at salvage yards and see if you can pick up a 6L running engine. You will need it with ECU and wiring

cheers
Warren

 

Found something interesting today when I pulled out the remaining plugs. All plugs were clean, no sign of water in the cylinders.
I put a little oil down the holes and put in a battery. Lo and behold it turns over smoothly! The battery is weak and won't hold a charge even though it's new. It's a Walmart special so I'll take it back and exchange it.
So, no water came out the plug holes when I spun the engine, no binding, grinding, crunching noises whatsoever, which is encouraging.
HOWEVER....
Under the distributor cap I found the amber colored plastic shield was partially melted, along with the soft rubber plug that wraps around the wires to the magnetic pickup. There was obviously some sort of fire inside the distributor, but it must have been brief because the cap, rotor and wires themselves were undamaged. I'm assuming there was a buildup of gasses that leaked past the shaft and ignited? I'm rather suprised considering there are two vacuum hoses attached to the cap to evacuate the gas. Is this a common problem?

 

I'd compression test it just to make sure, this will also give you an indication of a valve seat issue, replace the parts in the dissy and see if it fires up.

 

I plan on the compression test anyway, considering I have all the plugs out already, I think I'd be foolish not to.
If the pressure tests are good, I'll try to get it running to make sure there aren't any other issues, then proceed to replace the wire harnesses. I haven't checked for the infamous seized distributor centrifugal weights yet, maybe this weekend when I have time.

 

I finally got a few minutes to play with the car again today. I removed the oil drain plug and....out came about 2 or 3 quarts of crystal clear water.
At first I was crestfallen, but I realized that if it were a cracked block or blown headgasket the water would be green, so this must be rainwater leaking onto the engine as I had hoped.
Considering the water hasn't been in there for very long and the engine hasn't been run with the water in it, I'm beginning to raise my hopes a bit. After I do the pressure tests, I'll flush it out, replace the oil and see what happens.

 

Awww crap.
I suppose water exiting out the spark plug hole and from the oil drain plug is a bad sign, wouldn't you say?

 

The absolute MINIMUM attention you should give your engine is a heads-off and sump drop inspection. Water in the wrong place will do a lot of damage.

 

Yeah, I'm trying to decide if I should pull the head on that side, both heads, or just pull the engine for a complete tear down, or replacement.
I don't have a garage, so I can only work on it during good weather and keep it well covered the rest of the time. It sucks, but I've been doing it that way for years.

 

Not a good sign - but before you panic I would do as Fraser suggested and get the heads off, there is no point in only doing 1 side, I rebuilt 1 engine on my boat and guess what the other failed dropped a valve VERY soon after.

A set of reco heads here in Australia are about $2000 a set see ebay here
http://cgi.ebay.com.au/Jaguar-V12-cy...item439a5f791a

If the damage is terminal there are a couple of options

1. Lump it with a Chev, I was going to do this but that V12 is soo sweet I decided not to.
2.Buy a good running engine from a salvage yard, you will usually get some kind of warranty

good luck and let us know how you go

Warren

 

The compression check was dismal to say the least. The cylinders had either no measurable compression, or had such low numbers as to make them worthless. The highest number I got was 60 psi. I can only assume the block is twisted from overheating.
So, next question. I may have found a couple used engines, however one of them is out of a 76. What differences are there between the older V12's and the one in my 83 H.E. other than compression? Will there be sensors in the 83 not found in the 76? Will the transmission bolt up?

 

Oh...and I apologize for being such a pain. Finding reliable information about the nuts and bolts of Jaguars has been interesting to say the least!

 

Anyway you cut it you are going to have to strip down your engine, in the last resort to use some of its parts on a mix-n-match engine if you buy the two others you mention. A '76 will have the old type pistons and heads.

Why do you think the block is warped ? Lack of compression is probably due to stuck piston rings and other corrosion.

Transmission not a problem, the bell-housing mounting is the same at the engine, but the bellhousings themselves will vary according to the transmission fitted.

 

Hey Jamie,

the 76 will also have a rope rear main seal , there is a procedure to replace this with a ford unit I think or could buy a used later model with the lip seal block here is one on ebay for $500 so far.

http://cgi.ebay.com/ebaymotors/1990-...Q5fAccessories

There are also lots of mods you can do in rebuilding such as machining for Ford 460 main bearings. Depends on your budget but this would also be a good time to add some cubes. You can have the crank welded and reground for 78mm stroke gives 6L and the original liners can be bored to 93mm gives 6.3L with 78mm stroke or 5.7L with standard stroke.

Here is a link to a guy who has done some pretty neat mods including Wolf ECU and distributorless ignition. Depending on how tech savy you are there have been a few guys who have used the Megasquirt ECU and dual Ford EDIS 6 ignition modules to run the Jag V12.

http://www.ichi-intl.com.au/Personal...ds%20Index.htm

hope this helps

BTW I have a complete set of XJS manuals so if you have any questions just ask

cheers Warren

 

Warrjon, that engine on Ebay is a 1990, which is the 6.0 isn't it? Are they the same as the 5.3 engines, just bored out to higher displacement? Or are they a completely different animal? I assumed that the 6.0 was completely different and even used a different bellhousing?

 

The 1990 will be a 5.3L, there is not a lot of difference between the Marelli 5.3L from about April 1989 (my car is a Marelli 5.3L and its a April 1989 build) and the 6.0L. To get the 6.0L the stroke was increased from 70 to 78.5mm the 5.3 Rods were retained but the pistons have a reduced pin to crown height to allow for the extra stroke. The liners are also slightly shallower.

The bellhousing is the same for all of the GM transmission V12's Jag changed the bellhousing from the BW to the GM in the late 70's early 80's can't remember the exact time.

The 6.0L also came with the GM4L80 4 speed auto, if you could pick up a good running 6L with trans at a reasonable price it would worth it, don't forget you will need the ECU and wiring otherwise an aftermarket ECU would be needed.

Here is another link to AJ6 its got some good info on the V12 including bore and stroke's that have been used GET this, the Jag v12 is capable of being bored and stroked to 10L, was used in aircraft. There goes the reliability argument who would put an engine in a plane that was going to fail.