You should see an abnormal running temperature rise & back off immediately. You need to watch your temperature gauge like a hawk in the early days after a rebuild. If the vehicle runs on the hot side you know it's tight/lean and needs very careful driving until temperature is stable ~ richen mixture if necessary. Jaguar's old run in procedure should be ignored with modern lubricants. Run in on a max SF mineral oil. If temperature is stable at around 70 degrees after the first 300 Km's (limit RPM to 3000 until then) give it bursts at full throttle (not RPM) watching temperature ~ back off if temp rises excessively. Avoid constant throttle driving so that on over run you draw oil up into the ring belt. Change oil at approx 1500 Km's & then you can move to premium oils or synthetics. If you want to adopt a belt & bracers approach delay the first change to 2000 Km's. Continue to drive sensibly with increasing use of revs. The engine should be fully broken in by 4 to 5000Km. This is a little excessive but ultra safe.
With modern lubricants you can battle to run these things in and end up with an oil burner. Don't run the engine lean. Don't try & run in on premium oils. They protect too well to achieve proper break in. Don't be too gentle with the engine after the first 300Km's
Boroscope will tell you if you are too late
If you have got to 3000 miles your engine is just fine & you can demand full performance & RPM very safely. Using Mahle's recommendation was wise. They know their piston metallurgy. I've said from the start of these threads use Jaguar clearances or those of the piston supplier.
EDIT: Never lug the engine. Rather use higher RPM than recommended.
OK, I have written to Hepolite requesting they give us their recommended piston to bore clearance for a 1965 Jaguar 3.8 litre XK engine.
I will publish their response here.
Let's clear this up & move on. Mahle have of course done the right thing by providing it.
I'm having a right run around here but what looks like the official Hepolite site is for Motorcycle pistons only. They are completely divorced from Hepolite Automotive pistons from some further reading. Peter ~ you might be interested.
Be patient ~ at least they responded. I have been given 2 other contacts for Hepolite Automotive pistons. Lets see what they have to say.
BTW my genuine Jag pistons were made by Brico. They were swallowed by Federal Mogul in 1998. My restorer found a box.
Unfortunately, 'Hepolite' seems to have gone the way of many, notably Dunlop, and been reduced to a trademark, a label, separated from its original manufacturing and technical base, that is bought and sold purely for the goodwill value associated with the name.
BTW my genuine Jag pistons were made by Brico. They were swallowed by Federal Mogul in 1998.
As Brico made the pistons, the rings, and the liners, no doubt they had sufficient knwledge to be able to specify that very small clearance of .0011 to .0017. There's an old rule of thumb that, if the clearance is much different from the bore divided by a thousand, check that you haven't made a mistake.
All new HEPOLITE automotive pistons have the piston size and minimum clearance marked on the piston crown. The clearance is the "SP" number, in this case it is 0.03mm
3.4 piston marking example, could not find a 3.8 ~ excuse weight matching scriblings by a chap at Jag-lovers.
On Mon, 20 Sept 2021 at 14:00, Glyn M Ruck <gmruck@lantic.net> wrote:
Dear Sirs,
See below. Could you please provide your recommended
Hepolite piston to bore clearance for a 1965 3.8 Litre Jaguar XK engine or
do you suggest adhering to Jaguar published specs.
Dear Sirs/ Madams,
Could you please provide your recommended
Hepolite piston to bore clearance for a 1965 3.8 Litre Jaguar XK engine or
do you suggest adhering to Jaguar published specs.
Kind Regards,
Glyn Ruck.
As Brico made the pistons, the rings, and the liners, no doubt they had sufficient knwledge to be able to specify that very small clearance of .0011 to .0017. There's an old rule of thumb that, if the clearance is much different from the bore divided by a thousand, check that you haven't made a mistake.
Yes. It's like the old plain bearing rule of thumb for clearance. Thou per inch shaft diameter plus 1 thou. I think the whole SA mining industry runs on it. ~ Scotsmen engineers.
