Hi Martin,
Pushrod 3 1/2 Litre? And not an XK 3.4L?
If it’s a pushrod block and usable I am interested of course, DHL from Germany is not that bad.
And no customs nor taxes (except for the freight there is of course VAT)
Thanks!
Hi,
I will get back to other parts later, but now I am trying to get standard size 3 1/2 Litre piston set (apparently made in UK) for my project, 82mm I believe. (From Worcester Classic Spares)
I was tempted to get a standard set of XK 3.4L 83mm pistons, it would cost less than half, fit the con rods I have 100% and give more cc and power, right? But original size should last longer, I hope.
Cheers!
When my engine was rebuilt in 1970 it was bored out to 83mm plus 20 thou. The XK 20 thou oversize pistons have been there for the last 50 years with no problems!
Denis
There is no reason to believe that: 82 vs. 83 mm in a decent block, and either should last well into the next owner’s stewardship.
I wouldn’t put split skirt pistons in personally
I’ve never had trouble with them bored out.
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Pekka,
I guess split skirt pistons may be more likely to fail under stress. I wonder if piston failure may be in part due to oil failure resulting in partial seizure?
Just out of interest were you using mineral oil, semi-synthetic or fully synthetic oil?
Peter
Pekka, does your engine have valve stem seals? If exhaust valve heated enough to stick open in guide, then first noise you heard might have been valve hitting piston, second noise on restart was more extensive damage?
Hi everyone,
Good thoughts, I will ask if the pistons are split skirt (hopefully not, anyone know which standard size 82mm pistons Worcester Spares would supply?).
I have been running Castrol SAE 30 mineral engine oil for 15 years.
Yes the 83mm +0.030" overbore lasted at least three ownerships (Colorado, Florida, UK/Finland) and over four decades.
Not sure what failed first, I have the exhaust valve, yes it was stuck, evdn without the dish (I found 50% of it in the oil pan, can post a photo) the piston is in bits and pieces, the gudgeon pin is still there in the con rod and one side if the piston, one locking ring is still in situ, the other one was found in the sump, yes the failed side of the piston is on the exhaust side as is the hole in the cylinder.
Cheers!
Soooo, I should just get standard size 83mm XK pistons (easy and cheap) and have liners fitted in the block? Instead of getting expensive 82mm standard size pistons and having liners fitted (total ca €1000,- euros for the machine shop) right?
Oh well, lets see where this will take me.
Cheers everyone!
1mm difference, which translates to 0,5 mm/ radius, which is ~0.020".
On a stock block, don’t see why not.
Pekka,
I’ve been running my SS on fully synthetic for the last 10 years and it has split skirt pistons. Fully synthetic oils don’t break down under stress like mineral oils. They are more expensive but I think the benefits are well worth it.
It’s quite possible that partial seizure was not the cause of your piston failure but apart from having better properties under stress synthetics also have other useful advantages. Most normal wear in the past occurred at cold start-up because mineral oils drain off bearing surfaces.
Synthetics have been designed not to drain off and tests over hundreds of thousands of miles have shown dramatically reduced engine wear over the use of mineral oils. Don’t be put off by the lower viscosity. I am using 5W-30 and my running oil pressure always remains above 40 psi regardless of how I drive.
I also changed to fully synth for the gearbox 10 years ago with no regrets.
Needless to say my Reliants were running on mineral oils when they failed.
Peter
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Synthetic oil is thinner when cold and more quickly reaches where it’s needed than mineral.
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Synthetic oil doesn’t dissolve in petrol so reduces bore and ring wear, which is a problem when the choke is out or the carbs flood.
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Synthetic oil maintains viscosity to much higher temperatures and pressures, so might prevent a seizure in an overheating engine or maintain oil pressure when mineral oils won’t.
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Synthetic oil clings to surfaces for longer so that an engine left for a long time will have better protection of cams, tappets, cylinder bores etc when you start it.
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Synthetic oil can withstand high pressures so that cam and bore wear is reduced.
For normal use, I’d have no issue with split skirts: for sustained, spirited driving, non-split would be good insurance.
Hello
I was once told by an old Jaguar man in Sydney that he recommend drilling a 1/16" squirt hole through to the oil galley in the conrod, 1/4" to 3/8" max down from the bottom of the skirt of the piston on the exhaust side of the conrod, ie thrust side. I have not done the process but wonder what the experts think?
Cheers Peter
Not a chance I’d drill a hole, mid-rod: down on top of the big end…maaaaybe.
That would have been Jim Wilson. And he would have prefaced it by saying “Are you listenin’ young Peter,as I’m only gonna tell you this once”
I’ve said it before, but I guess I’ll tell you guys this twice, only this time with pictures. 
Here is a C1049 aluminum con rod with offset oil tube, as was used in early 3.5 Mark V engines up to T6790, and Mark IV and SS.
Here is a C1144 con rod bearing as was used in the above C1049 con rod. Notice the offset oil hole.
Here is a C2844 aluminum con rod with a center drilled oil passage, as was used in 3.5 Mark V engines T6791-9999 and Z1501-2198.
Notice the groove inside the wrist pin hole. You should not need any additional shade tree mechanic’s hole in the side to lubricate the wrist pin.
Now to the problem. The factory used the same C1144 bearing with offset oil hole in these C2844 rods. Here is why that was wrong.
Reduced oil flow through that passage would lead to reduced oil at the wrist pin, especially at high speed, leading to heat, drag in the pin, fatigue loading and eventual fracture of the piston and/or the rod.
The C2448 steel rods used in engines Z2199 to the end have a center drilled oil passage, and the C1132 bearings also have a center drilled hole. But the anti-rotation tab is on the other side, so they don’t fit in the earlier rods.
So the problem was reduced oil flow at the wrist pin.
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Thanks for the pidgers!
Interesting that the oil passage was offset.
Hi!
Ahhhh, you seem to know how I drive! 
I have all pistons and con rods out now. Pistons nr 1 and nr 2 were fine, Nr 1 was really really clean, all the others had some black deposits. The two top rings were stuck on piston nr 5. Nr 4 was in bits and pieces. The con rods are not all the same, but I think they all are XK con rods. Nr. 4 may be slightly bent anyways. 
Cheers!
I love the display case! 
Can you tell if there was any blockage in the small end oil feed?
Peter