Guys
I am in the process of assembling parts for an engine rebuild, in order to keep me occupied in my fast-approaching dotage when petrol (gasoline) is outlawed/prohibitively expensive and/or I am too old to drive.
In this matter I have been researching cylinder liners. Now the 5.3 litre V12 engine, right through from the E Type V12 and Series I XJ saloon V12, uses the same liner; but NOT the same pistons.
In all these engines, the liner and pistons used to come as a matched set, called A or B specification. Each engine was fitted with ALL A spec or ALL B spec pistons and liners. The engine number (stamped on the crankcase just at the rear end of the V) on our V12 engines ends in HA or HB. The A or B signified whether the engine has A or B spec pistons and liner sets.
The specification from the factory manual of the two sets is as follows:
A specification liner internal diameter: 89.98mm = 3.543 inches
A specification piston clearance to liner measured half way down liner bore across the bottom of the skirt: 0.03 to 0.04mm = 0.0012 to 0.0017 inches. A spec pistons for HE engines, at least, are stamped with an A on the piston crown.
B specification liner internal diameter: 90.01mm = 3.544 inches
A specification piston clearance to liner measured half way down liner bore across the bottom of the skirt: 0.03 to 0.04mm = 0.0012 to 0.0017 inches. B spec piston for HE engines are stamped with a B on the piston crown.

Therefore, a B specification piston may not physically fit in an A specification liner! If it does, it will have far too much friction.
Similarly, an A specification piston in a B spec liner will be loose, with a good chance of most un-jaguar like piston slap, even if it will produce more power as a result of lower internal friction! I am indebted to AJ6 engineering for explaining these points to me.

Now, what to do in the event of needing to replace a liner, as both A and B piston/liner sets are NLA from Jaguar? Well for pre HE engines, some piston and liner sets are available, from decent aftermarket makes, mostly Mahle. All good, EXCEPT they come in matched sets at 90mm liner internal diameter. There are no aftermarket A and B spec liners.
Therefore, for HE engines, even though the liners are the same in principle as pre HE engines, aftermarket liners do NOT come in A and B specs, neither are aftermarket HE pistons available. Assuming the pistons are OK, an A spec piston would fit in an aftermarket 90mm liner, but the piston skirt to liner clearance could be out of spec on the wide side by 1 thousandth of an inch.
However a B spec piston would be too tight on a 90mm liner and would be out of spec on the tight side by 1 thousandth of an inch.

If I had an A spec engine (mine is B) I would be prepared to risk an A spec piston in an aftermarket 90mm liner. But I am not willing to risk a B spec piston in a 90mm aftermarket liner, as being too tight is courting disaster. So what to do?

First of all, the chance of even a single duff liner in a 150,000 mile V12 is very small. Grant has rebuilt half a dozen and only ever found two bad liners, both in the same engine. Stories from the JEC mag are full of the factory hone marks being completely unworn on 100,000 mile engines that have been stripped down. Still and all, it is a worry if it turned out fate had been unkind. Additionally, liner ovality is always a possibility.
So I googled up and found the following things:
A well known motor factor in England can still get them made by the original OE supplier, but ONLY in A specification. All my pleading was to no avail to get them to make B spec ones. These are the guys, ask for Douglas, a very helpful guy:
https://www.mytonautomotive.com/engi...2-engine-75701

Additionally I found a mob in the USA in new England who, miracle of miracles, has TWO genuine OE, HE engine, B spec, new old stock liners for sale. These have been swiftly acquired and are now happily settled in France! Take a look at them on the supplier's video:
https://www.sportsandclassics.com/ja...liner-unboxed/

So I have two new liners if I need them, and if I need more, I have a new unworn sample I can give to a UK liner maker who say they can make anything! https://westwoodcylinderliners.co.uk/bespoke-liners/

And here is a snap of the refugees from the USA, proudly standing on Madame's kitchen table:

Interestingly, these brand new liners are not yet honed for oil retention. Luckily I have a Flex-Hone in stock for this requirement, if a new replacement liner is needed.




Finally, "what if you have a duff piston?", I hear you ask. Luckily, some years ago i bought an entire set of 12 B spec pistons, that had been used in test-bed engine for a very short period only! Interestingly, they have their skirts coated in a teflon-type feeling material; but I shall use them if I need to.

 

I think the government will outlaw / tax your car long before they outlaw you repairing your car. I've shipped many parts all over the world to places I cant pronounce labeled "tractor parts" to avoid taxes. I understand you may like to collect parts but of all the things to collect in anticipation cylinder lines are far down on the list of common fails. If you want to be prepared I'd suggest a complete good engine can be stored in a shed or covered well in an out of the way area. A complete engine or two will much better insurance in the long run.

- John

 

Agreed, and I do have a spare engine, but it is A spec! Additionally, I have a sentimental feeling about rebuilding my original engine, which is why I am doing what I am doing. Not that it needs it, you understand!

 

You got me curious so I went out and looked at the motor sitting in the garage I pulled from my '88 H&E parts car.
The numbers at the back of the 'V' are: 8S52862SA

No HA or HB in the coding there or anywhere else.

PS...I got the parts specifically to protect against the unlikely event of a catastrophic issue with my engine. Figured it would be better to have one handy than to have to go scrambling around trying to find one in an emergency.

 

Brad
The A is the important thing. The H part I do not think matters for these purposes. Somewhere on the web there is an engine number decoder for the V12.

 

I think the SA and SB signified 9.0 comp. ratio while HA and HB were 10.0 ratio.
As Greg says there is plenty of online info regarding the numbers and suffixes.

 

Mine is 12.5:1 He Baxtor, so i expect they used these on both engines!

 

can you 'hone out ' the tighter spec A liner to take the larger B piston ?

BB

 

No idea, maybe it is possible to accurately machine 1 thou off a liner diameter (ie cut 0.0005 thou off the inside surface all round) maybe not? Perhaps someone on here can tell us?

 

My engine is 8S 56504 SB. (Hess&Eisenhardt, origin of the car was UK coupe 1988)
The engine decoder and website https://www.automobile-catalog.com/ says it's set B and the ratio is 11.5: 1.
So where is the truth and where does the ratio change (from 9 to 12), if the HE engine is, for example, set B (pistons and liners) and it is always the same size?
Crankshaft, connecting rod, head ?
Furthermore, does the ECU number depend on the size of the ratio? (Set A or B)?

 

As I understand it, HA & HB = High Compression. Whereas SA & SB = Standard Compression.

Because the engines changed compression ratios for the HE variant, that means for pre-HE, SA & SB = 9.0:1 CR. And HA & HB = 10.0:1 CR

From HE engines, SA & SB = 11.5:1 CR. And HA & HB = 12.5:1 CR.

But then to make it more confusing, after engine 8S72157 the Suffix letter relates to Emission Type rather than Compression Ratio!

Paul

 

The MAJOR ratio change on 5.3 litre engines was between the flathead pre-HE engine (whether carburated or injected) and the HE engine which has a completely different head and a minimum compression ratio of 11.5:1. Most early HE engines outside of North America had 12.5:1 compression ratios.
Pre-HE V12s (so-called flathead engines) came in a variety of compression ratios varying from as low as 7:1 and right up to 10:1 for a very few late pre-HE engines made just before the HE engine was launched.
The ECU I.D. number does not refer to the engine compression ratio. For example, the 6CU (the one used in early V12 HE engined cars) and the 16 CU ECU model used in all later 5.3 litre HE engines, are completely interchangeable regardless of compression ratio - though not necessarily interchangeable if 02 sensors are fitted.
Both 11.5:1 HE engines and 12.5:1 HE engines were fitted with either A or B piston sets, as were pre-HE engines. The set fitted has no bearing upon the compression ratio.
All HE engines had a minimum of 11.5:1 compression ratios.
Early V12 HE-engined Lucas ignition XJS cars destined for USA and Canada had 11.5:1 ratios as the fuel there was considered not quite correct to support 12.5:1 ratio engines
UK and (as far as I know) RoW early XJS HE-engined cars, up to about 1987/88 when the Marelli ignition replaced Lucas, all had 12.5:1 ratio engines.
From the time that Marelli-ignition engined HE V12 XJSs were built (about 1987/88 from memory, someone will have the exact VIN number) ALL HE V12 engines had the 11.5:1 compression ratio.
I believe I am correct in saying that the ratio change was effected by using slightly different pistons, the heads were unchanged on all 5.3 litre HE engines, regardless of compression ratio.
Crankshaft and connecting rods are dimensionally identical on all 5.3 litre HE engines. Indeed, they are dimensionally identical on ALL 5.3 litre V12 engines, regardless of whether carburated, injected, pre HE or HE versions; except for detail changes on the flywheel end depending upon whether manual, or automatic, which type of automatic, and such things.
I am informed by someone who is pretty sure it is true but not 100% sure, that the H and S markings before the A or B refers to the market for which the car was destined, not anything directly to do with the engine itself. BUT, see PTJS's post immediately above, which may also be true!

 

Yes, that would be quite easy. You could do it in your home garage with a rigid hone and a heavy duty drill. Be careful not to hone too much, it is easier to remove material than to put it back!

 

All clear, thanks Greg.

 

Great info, thanks Greg.
I wonder why the compression ratio was dropped to 11.5:1 in 1988 with the introduction of Marelli ignition (which was surely an upgrade) - struggling to think of a reason!

 

According to AJ6 Engineering, they concluded that the 12.5:1 was more compression than needed, and that reducing it to 11.5:1 had no material effect, and, of course, it standardised all the engines!
I have driven a USA-model Lucas car (but changed to UK spec with no cats, no o2 sensors, and with the AJ6 super enhanced ECU and throttles etc) and it seemed to me to go as well as mine. So I suspect the USA cars' lower factory BHP performance stats were down to those things, not the CR.