I have posted 5 pages above.

I will provide Cylinder Head/Camshaft material when needed.

 

If you end up needing new pistons, disregard the Jaguar skirt clearances. They are too tight for modern aluminium alloys and almost certainly result in a seized engine. I've personally seen two examples recently, one a 3.8 the other a 4.2. The clearances need to be larger.

 

What brand of pistons? Was that in genuine 3.8 Brivadium sleeves?

 

Both sets of pistons were AE Hepolite. One was reasonably recent production, the other was NOS, probably from the early 70's.

4.2 was in a 1970 E Type, and as far as I know the original block/liner. 3.8 had been resleeved with sleeves made by Westwood.

 

Mahle would have a heart attack with that comment. My engine still has it's genuine Brivadium sleeves which I bored 20 thou with NOS Jaguar pistons out of genuine dark green Jag Box. Bought over 25 years ago.

Uses no oil & runs as cool as a cucumber. Tight engines should immediately have shown raised temperatures long before seizure.

What are people doing to open clearance? Overbore? Or using one of the 5 piston grades which I thought was only applicable to standard pistons?

 

When I bought my car it had been apart for at least 20 years. The engine was sitting on a pallet, and when I took the head off there was 3" of water sitting on top of one piston. I ended up needing to resleeve, new pistons and a different head, as it was quite corroded. I would have like to have kept the original liners, but it took 40 tons in a hydraulic press to get the piston out and it scored the liner; plus the corrosion was over the rebore limit.

 

Yes. The 3.8 could only be bored max 30 thou. The 3.4 could go 60 thou.

 

The machinist said the corrosion hadn't cleaned up by 80 thou. It was new sleeve time.

 

Sounds like crap QC to me. If you open piston to bore clearance you are are almost guaranteed slow run in of the chamfered top & 2nd ring & an oil burner.

 

The machinist I went to the second time said that he had had problems using the Jaguar spec of 0.0011-0.0017" skirt clearance, instead he went to 0.0025" and never had any complaints. After I went to that for the second set of pistons it broke in nicely and I can use 5W30 oil with no consumption or smoke. The machinist did mention that the diameter of each piston in the new set of 6 was different, so he machined each bore to match and have a consistent skirt clearance. He returned them all in numbered boxes to match the bore and gave me stern instructions not to mix them up. He was also aware of the XK's numbering convention.

My usual trip is Calgary to Vancouver, BC and back, and I monitor oil consumption. It's a road with many mountain grades, so the engine gets worked hard and gets hot, and about 1100km each way. The S Type didn't use any oil, and it also has no valve stem seals. Does have modern bronze inserts though. Every other XK engined car I have driven that route I need to add oil part way through.

 

He obviously did a very good job of matching pistons to bores & you had a good tight set of rings. Always good to hear a happy story. I kept my tight piston to bore clearance (& consider it a best practice) & all is well but I monitored the whole process & Plastigauged every bearing clearance. Old habits from running race team days. You should be able to run a 5W-30 synthetic happily in these engines in top condition & have decent oil pressure. I'm about to change to a 10W-30 Synthetic with a heavy overdose of Mercedes 229.5 additive in it. Running in on a monograde mineral. You would never run the thing in on my racing blend. Studiously ignoring Jags run in procedure with minimal constant throttle, frequent lift offs & bursts at full throttle. Nearly there. Covid messed things up.

I don't need a 5w with our mild climate so my oil is virtually VI Improver free.That said I would be quite happy running a 5W-30 or 5W-40.

 

I like to use a 5W simply for the cold pumpability on startup. My S is a summer car, so it sits for about 6 months at a time in winter storage and when I start the car I want that oil up in the engine as fast as possible.

I have fitted a block heater to warm things and it does make a noticeable difference to cranking speed, but my winter storage facility doesn't have the ability to plug the car in for the first start of the season.

 

Oh! You are spot on for your ambient conditions.

I've been giving this whole story some further thought with all the gaps you have now filled in.

I'll bet that Hepolite have botched up here and that your normalised operating clearances fully warmed up are a lot tighter than you think.

I would equally bet that Mahle pistons would react differently. I'm going to check it at some time..

NOS pistons should not seize at recommended Jaguar OE clearances.

 

I'm sure that's the case. It ran fine while I was tuning and driving at low load on city streets. The first time I took it up a long hill and needed to give it more throttle is when it seized. It was the sort of sound where I put the clutch in and had pulled over before I realized I had done it. Let the car cool off and I was able to restart it and gently drove it home, but the oil was full of metal. Had to pull the engine and strip it down again, it had under 200 miles on it.

 

Ugh! I pain for you. A typical heat seize if she would turn over once cooled down. More typical of 2 Stroke racing motorcycles tuned at the limit when they run into oxygen rich air under trees & go lean.

 

I can't find the photo, but the aluminium was smeared all along the piston height where it rubbed in the bore, including metal covering the rings. It wasn't pretty. I was fortunate that the bore wasn't damaged, just some superficial marking, no actual wear. I was able to get away with new pistons and a complete cleaning of everything.

 

Lucky ~ with racing 2 stroke bikes it tears all the Nikasil off the bores.