STARTING NEW THREAD: I HAVE NEVER DUG SO DEEP INTO A V12 ENGINE SO I WILL NEED ADVICE:
I removed the blown engine from the car yesterday so now I have both engines side by side on engine stands. I will call the engine from the car Engine #1 and the Spare Engine #2
Before I go further, Engine 1 is a A series and Engine 2 is a B series. Engine #1 is Marelli and Engine #2 was Lucas.
THE PLAN:
Engine 2 had a dropped valve seat which damaged the head and the piston on Bank B Cyl #1
Since Engine 1 was a perfectly running car until it got destroyed after an oil change?? I want to swap some parts from Engine #1 into Engine #2
a. Remove a piston and liner from Engine #1 and install it into Engine #2. Renew all big end bearings if needed. What do I use to to seal the replacement liner? Any advice on this part of the job is welcome.
b. Remove the heads complete with Camshafts from Engine #1 and install them on Engine #2.
c. Remove damper assembly from Engine #1 and install on Engine #2
Question. Is the Marelli car's flex plate (drive plate) different from the Lucas? How does the ESS (speed sensor) read the engine RPM? Is there a special tooth on the ring gear that triggers the RPM reading? If it is the standard flex plate I will leave the one on Engine #2. If not I will swap them over.
Once the above is done, the reassembly will begin.
All new gaskets and O rings for the engine.
If any of the above is not doable please let me know.
Also, I will also want to flush out the oil cooler and lines. Is this possible or should I replace it?
Recommendations needed.

 

Sanchez
Flex plate is the same on all GM400 5.3 HE engines.
Speedo drive question: Do both cars drive the speedo from the rear differential, or does the Lucas one drive it from the gearbox?
A and B for the engines just refers to the tolerances of the piston and liner set. As long as you remove the piston AND its liner and replmace it by a piston AND its liner to do the swap, all will be well. It does not matter if an engine has a mix of A and B piston/liner sets as long as each cylinder has one of the other.

Palm has stuff on the liner sealing.
PLEASE takes lots of photos and post as you go along!

 

Adding to Greg's post and my thoughts from way down here.

I am assuming both engines are USA spec engines ??

My reasons are that the Lucas engine is more than likely 11.5:1 Comp ratio.

GUT FEELING, is that the Marelli went to a lower comp ratio world wide, BUT, only a gut feeling.

That would have a lumpy running engine for sure.

SOOOOO

Paul, PTJS1, will have the answer when he wakes up and gets some coffee in him.

All the rest looks OK.

 

@Greg and Grant: Both engines are MY 1990 XJS' so the presumption is that both were diff driven speedos. I do not think that matters as I am bolting the tranny from Engine #1 to Engine #2.
Also, I have not looked deeply into this but do I have to replace the timing chain cover from Engine #1 to Engine #2 to facilitate the installation of the the front crank sensor?
I have a hard copy of 'Palm' so I will read up on sealing the liners.
From what I have gleaned: "Whether Lucas or Marelli, the engine blocks are the same. Series A and B blocks only denotes the variance between piston and liner which varied 0.0001. Maybe my interpretation of what I read is wrong, but the consensus is that piston and liner from either series must match. Can I remove the piston and liner as one unit or should it be separated and installed liner first then piston. One other thing to note is that the standard piston rings are the same for either A or B engines. I hope I am right. "Looking" at both engines, they look the same. Combustion chamber in the heads; piston crown flat, but I am pushing 74 so my eyes may be deceiving me. I don't know much about the comp ratios of Lucas engines compared to Marelli engines. My thought is that the names Lucas or Marelli refers to the type of ignition systems used on these engines. You all are the gurus of these engines so I have total confidence in every comment/post made by you all. RESPECT.
On another note regarding valve seats. Should I remove all the valves on the heads I am going to use to inspect the valve seats? What am I looking for? Is this just extra work?
I don't want to install heads, which I know very little about and have a valve seat drop down the road.
Should I install new piston rings or should I leave them alone. Looking to save some $$ here.
BIG ?: I have to turn the engine I am going to use with the heads off in order to remove and replace the piston and liner. Will the method I used in the attached photo suffice or do I have to put another liner hold down on the other side.
In my other post, I mentioned while removing the head from Engine #2 it stalled 1/2 to 3/4 inch up and I had to cut 4 of the inner studs in order to remove the head. I successfully removed the cut studs. I am wondering whether I should replace all the studs on the engine I am going to use or just the bad ones. What say you?

this is what I am using to prevent the liner from moving

 

Also, I have not looked deeply into this but do I have to replace the timing chain cover from Engine #1 to Engine #2 to facilitate the installation of the the front crank sensor? No idea, but take a look at see, it will be obvious.
I have a hard copy of 'Palm' so I will read up on sealing the liners. OK
From what I have gleaned: "Whether Lucas or Marelli, the engine blocks are the same. Series A and B blocks only denotes the variance between piston and liner which varied 0.0001. Maybe my interpretation of what I read is wrong, but the consensus is that piston and liner from either series must match. Can I remove the piston and liner as one unit or should it be separated and installed liner first then piston. Removing the liner may not be easy. I advise FOR SURE remove the piston first. To remove the liner you will almost certainly need to get a mchine shop to make you a puck of the same diameter as the liner O/D with a step to a reduced O/D in it that fits inside the liner I/D. Then either whack the puck to push up the liner, or make a hole in its centre for (say) 18mm threaded rod, and protecting the deck with wood, wind the liner out using a thick piece of steel across the wood blocks, threaded rod and a nut under the puck and above the steel.

One other thing to note is that the standard piston rings are the same for either A or B engines. They are.
Combustion chamber in the heads; piston crown flat, but I am pushing 74 so my eyes may be deceiving me. I don't know much about the comp ratios of Lucas engines compared to Marelli engines. USA 5.3 HE engines are all the same CR. With the introduction of the Marelli ignition, ALL V12s became 11.5:1 worldwide. Originally, up to the Marelli intro, UK and ROW had 12.5:1 CRs.
My thought is that the names Lucas or Marelli refers to the type of ignition systems used on these engines. Correct, but instaling a Marelli ignition engine in a Lucas wired car may not be simple, as Marelli has an extra ECU to handle the ignition as well as the boot installed ECU. As long as you install a Marelli engine into a Marelli-wired car, no problem.
On another note regarding valve seats. Should I remove all the valves on the heads I am going to use to inspect the valve seats? What am I looking for? Is this just extra work? Leave well alone!
I don't want to install heads, which I know very little about and have a valve seat drop down the road.
Should I install new piston rings or should I leave them alone. Looking to save some $$ here. No need for new rings. The bores will almost certainly be fine and likely still have the factory hone hatching on them. Only if the bores are scored, OR if a huge wear-step at the bore tops above the ring max point need you do anything.
BIG ?: I have to turn the engine I am going to use with the heads off in order to remove and replace the piston and liner. Will the method I used in the attached photo suffice or do I have to put another liner hold down on the other side. I would do both sides for safety!
In my other post, I mentioned while removing the head from Engine #2 it stalled 1/2 to 3/4 inch up and I had to cut 4 of the inner studs in order to remove the head. I successfully removed the cut studs. I am wondering whether I should replace all the studs on the engine I am going to use or just the bad ones. What say you? Replace any badly corroded/eroded stud, if they are OK no need to unless you are going to race the car!

this is what I am using to prevent the liner from moving

I would decoke those piston tops! That is the dirtiest-looking piston top I have ever seen in a V12! What are the bores like, they should be coke free below the piston rings max height?

 

For general interest, the relevant extract from AJ6 Engineering's old website:https://www.jagweb.com/aj6eng/v12_performance.php

 

Greg. The cylinder bores are in good condition. I will "decoke' the pistons before reassembly. I will be attempting to remove the head studs that I need from Engine #1 to install in Engine #2.
I have a stud extractor which I successfully used to remove the 4 cut studs. I don't know of the stud extractor I used will damage the threads on the studs. I will try the 2-nut method first.

 

3rd coffee in, but I see that Greg has already done all the heavy lifting on the answers, particularly the compression ratios!

I'll bow to Kirby's statement on the .0001 difference on A & B pistons & liners, although that does seem a very fine tolerance? Everything I've read has always indicated that you must match pistons and liners. However, you really need to measure everything as you don't know if anything's been previously changed, so the A/B indicator may not be accurate for the engine in it's current state. Also the SA / SB indication for compression & piston size is APPARENTLY only relevant up to engine 8S72157, so check the engine block numbers.

As Greg has mentioned, I think installing a full Marelli engine configuration in a Lucas car would be more difficult than the reverse.

Good luck, and keep the pics coming!

Paul

 

Paul
Interesting point about liners. I actually have a B engine in my car, and against a possible engine rebuild as a prophilactic against boredom in advanced old age when Madame will no longer let me drive, I have four genuine NOS B spec liners in stock together with everything else needed including new rods, heads, tappet blocks, valves and springs; all genuine parts.
AS i was concerned about perhaps needing more liners, I bought some more new ones made by the same firm that made the Jaguar stocks. They only supplied A spec so i sent them to the top guys in Coventry to be sized to B. Having measure them all, they were ALL at least big enough diameter-wise to qualify as B spec! So no work needed!

 

Just to make things a little clearer:.
Engine #2 came out of a Lucas ignition car. What I got was the bare bones 1990engine with a dropped valve.
Engine #1 is the engine that came out of the car. This was fully wired for the Marelli system, hence my questions regarding the parts exchange.
All of the pieces to make Engine #2 Marelli compliant will be taken off Engine #1.
The Marelli electrical harness is in the car.
As far as the engines go they are basically the same except for the "SA" "SB" designation.
Also I need some clarity on the flex plate. Greg said that all the V12 flex plates are the same. How does the rear sensor read the RPM. Does it count all the teeth on the ring gear or does it look for a particular tooth on the ring gear to calculate the RPM. I am curious.

 

Greg,

That's intriguing! I looked through my docs but couldn't find a reference to the .0001 difference previously mentioned. Kirby's book mentions a "microscopic difference. I'll do some more digging and see if I can find what the specs and thresholds are for A & B size pistons and liners.

Paul

 

@ptjs1: After my last post, I was thinking that instead of going through all the work to remove the 'A" spec piston and liner to fit it into the "B" spec engine, wouldn't it be mor cost effective to purchase a "B" spec piston and re- ring all 12 pistons and new big end bearings(this was my plan all along). This way I do not have to get into liner removal/replacement issues. The liner with the damaged piston has no damage so I should just leave it be and get the "B" spec piston. I am going to clean of the piston crown and see what markings I find on the "B" spec engine.
PS: If the rings are the same for both the "A" and "B" spec pistons, the difference between the two must be minimal. Maybe the 0.0001 is the correct difference between the two.
Besides Kirby, I have seen this number in other posts by different people.

 

The first post in the thread below gives the math behind A spec vs. B spec. Worth a read.
https://www.jaguarforums.com/forum/x...rs-fyi-241438/

Jon