MKV 3.5 engine rebuilt

Hello Pushrod People
I am Wolfgang from Germany, so please excuse my bad english.
In my former life I was common with the XK engines, but now I got my first pushrod Jaguar. Very nice car, engine was overhauled 4000mls before…but this was 40 years ago. Nobody knows what really happens.
The engine is completely dismantled, except cam bearings.
The reason to remove the head was a half pint of coolant fluid coming out when draining the engine oil.
The colour was the same like the coolant in the cooling system, a wrong fill up is very improbable. Nobody knows the time for this leakage volume, maybe years.
So I guessed the head gasket is broken and did a pressure leak test with shortened engine block (without cooler) and 20…30 psi air. With a stethoscope with open tube normally I can detect very small leaks. But it was tight. So I removed the head and the copper gasket seems to be ok.
But I saw scratches in the liners and “polished” areas 90° to the gudgeon pin.
So I removed the crankshaft and pistons. The pistons have some seizure areas under the slots under the oil scraper ring. Photos will follow.
The pistons have a mark “83” and this is the size of the bore. Du to the original bore of 82, it seems to be the 4th oversize.
I’m thinking about the next (and last) oversize or relining. Last one is 0,06", 0,05" is not available
But relining: There are two “ears” at the bottom of the original bores in the block. Does anybody knows what they are for? Or should I use new liners?
Does anyone knows a piston manufacturer except JP ?
I will post some photos tomorrow.
Thanks for your attention
Wolfgang

Hello Wolfgang,

You are correct to take your time making sure dimensions are aimed at good result with pistons and cylinders.

The block deck should show letter punchings at each cylinder, using “F”, “G”, or “H” to show which standard size piston originally was fitted to each cylinder. These punchings also can give you an idea of how much the block deck may have been skimmed previously in rebuilds. The same letter system was punched onto pistons, I am not aware of the factory pistons having metric stampings. An “83” on a piston also suggests previous rebuild with metric shop work.

An “83” indication would suggest 83 mm = 3.2677" which is 3.2677 - 3.2250 = 0.0427" oversize (40 thousandths) or 83 - 81.92 = 1.085 mm oversize, suggesting at least one prior rebuild. Page B.42 of the Service Manual for Mark V indicates the factory kept stock for up to +0.030" (0.76 mm) oversize.

It is up to the user to decide what oversize bore is okay for their engine block. Factory supply is only an indication of what the factory thought would be appropriate for inventory. I presently run in my Mark V a pushrod engine with 0.070" (1.778 mm) oversize cylinder bore in sunny Southern California. With a properly functioning cooling system I have seen no overheating issues with this engine.

While I have used JP for pistons some years ago, I now use:
Ross Racing Pistons

On the “ears” at the bottom of the bore, check the connecting rod and bolt clearance during rotation. And if you replace the conrod bolts, be careful to observe that they seat completely. For example, there are ARP bolts which don’t quite clear the conrod inner radiusing on the bolt deck.

Hallo Wolfgang,

You might be interested in this rather long thread:

I have had my 3 1/2 Litre MKV for 22 years by now and experienced head gasket failure in 2017 and cylinder bore / exhaust valve failure in 2019.

It turned out also my engine (a 1947 MK IV engine, but they are basically the same) had had the block overbored to accept 83mm XK pistons.

Also in the rebuild I went for STD size XK 3.4L pistons and new Mahle top hat liners.
And modified the crank and main bearing line bored to use Chevy small block Clevite 77 main bearings.

Cheers! Tsüß!

If you mean these:

Those are for clearance for the connecting rods as they swing around.

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Hi All,
thanks for your ideas.
@Pekka: This thread is like a bible for me, a lot of very good information
@ Rob: I should have known this…I was just wondering if new liners would be installed, that the ears have to be cut out in the same way.
@Roger: I took really a long time for my decision

My plan:
I wont´t use new liners, I give the block to an engine shop to hone it to the very next measure for roundness and good hone surface without scratches along the liner. This might be only 0,1…0,2 mm in Diameter.
Then I will order with this dimensions custom made pistons from Mahle forged blanks.
The conrods will be changed to steel ones, I got XK rods in the meantime.
The crank will be gas nitrided to bear the modern Chevy main bearings and the XK big end bearings.
Do you thinks its a good idea to reinforce the flywheel mounting with two additional screws? There are 4 dowel pin bores in the crank and just two are used.
What are the machine works for preparing the block or crank for the Chevy bearings? I dont got them yet.
I also will change the brass pilot bearing for a sealed ball bearing. I did this with a Tr6 engine with great success. There is an existing 12,5mm bearing which fits to the pilot end of gear shaft.
Also a new housing for modern crank seal at the clutch side is planed. For that I will use a speedy sleeve on the crank and build a little bigger housing for the seal than the labyrinth housing is. Did anyone do this before and has a drawing or data for this project?
Please don´t insult me for my plans, but I want do this only one time. Maybe some solutions are little oversized, but this car will not becoming a trailer queen, but a good drivable car also for journeys and maybe daily use without oil drops…these are in Germany not really welcome.

Thanks
Wolfgang

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Hello Wolfgang,

Good steps overall in your plans. Here are some comments on your list, in the same order as your list but not including all lines (I don’t have firm opinion on some of your steps).

Engine dimensions for cylinder roundness can be done on modern machines to a few tenths (i.e. a few ten thousandths of an inch, around 1/100 mm) both for circular variation in the cylinder and staying within that tolerance all the way down the bore. These engines often wear with elliptical and conical variations in the bore. When the engine cylinders are bored be sure to have temporarily-installed the valve tappet guides with screws to correct torque before the bore so cylinder distortion issues do not occur. In case you did not notice, the valve tappet guide screws come in two lengths, make sure correct length is used for each mounting point.

XK conrods can work fine.

Flywheel mounting has not needed modification in my experience. The dowels are important for centering, be careful about their dimensions and the holes in which they fit. Consider balancing steps for crank which include flywheel attached and also clutch attached. Clutch dowels also need care.

No harm in changing out brass pilot bushing with alternative. However, I’ve never had problem with brass pilot bushing.

Rear crank seal has not leaked in my experience. But piece of mind may follow your plan of changing the seal method. It would not be pleasant to discover rear crank leak in your engine and then need to take apart to eliminate leak.

However, the engine is likely to leak oil from various places. Making these cars free from oils leak seems possible but difficult (e.g., the breather tube will drip a little). Also, a Mark V parked for ten or twenty minutes will have some oil pulled into the cylinders and cause brief puff of startup smoke. Parked longer gives time for that oil to flow past the rings and down into the sump. For my car in California, I use three pans under the car in the garage since engine and transmission can drip from oil appearing anywhere ahead in the airstream and also the differential can have a little dripping. I am not constrained by local law on this matter and consider it partially rust protection and also not worth the hassle. I carry a cardboard piece to put under the engine and transmission where I would not want to leave an oil drip or two.

From about 2000 to 2010 I used my Mark V as my daily driver in California. I also used a Mark V from 1970 to 1975 as my only car. In both these periods I did not take it above 65 mph (110 kph) on the freeways. Nowadays I only use the Mark V rarely on the freeways since the typical speed now is either around 80 mph (125-130 kph) or nearly stopped and I don’t like to drive my Mark V above 65 mph or in stop-and-go traffic.

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