Summer of '99 I put a professionally done (one of The Lists favorite
suppliers) rebuilt engine into an '87 XJ-6. This is the car that my kids
have been driving to high school. I drive it occasionally just to see how
it’s running, and to keep up with the maintenance. They do not drive the
car
hard.
Here’s my problem. No. 3 plug continually fouls over a period of time, and
for all appearances, it’s from oil. I followed my usual break-in regimen,
using non-detergent single grade 30w oil for the first thousand miles. I
then changed over to a premium multi-grade, and for awhile was using
synthetic until the Jag-Lovers group convinced me it wasn’t worth it if you
change your oil every 3000.
The car has been driven in all sorts of varying conditions, including a
75-MPH run to southern California and back from Sonoma County. 1200 miles+
at freeway speed.
At 10,000 on the engine, compression was between 150 and 155 straight
across,
although the #3 plug came out fouled badly.
Engine now has almost 20,000 on it and compression (cold, with throttle
open)
reads 155-140-150-140-140-145 (rear to front) and the #3 plug came out badly
fouled again. The car was running like crap. Just changing the plugs makes
it run 100% better.
I have JPEG’s so you can see the plugs if you really want. Other 5 are
perfect. I took out the Champions, and put in NGK BP5ES. Slightly hotter
plug for mostly around-town driving.
What do you people think? Did the rings in #3 cylinder never seat? Do you
guys stagger the ring openings around the piston like I always used to do on
assembly, or was I just being superstitious back when I rebuilt engines on
my
own?
I have juggled the injectors around, and, as expected, there was no effect.
I also suppose the apparent drop in compression means it’s time I checked
the
valves, but that is not going to affect the oil fouling in #3.
What’s the take, from the assembled cadre of geniuses on The List?
Regards,
MilesDate: Sun, 25 Nov 2001 01:34:54 EST
Subject: Piston rings seated, or not?
For that type of symptom on the number 3 only IMHO, especially since you
flowed and swapped the FI, as a must do, I would include the distribution
system and plug wiring as a primary foul-out candidate. Switching #3
wire with another that reaches would be a start but the dissy cam lobes
and what ever they trigger should be checked too! Next in line would be
the rotor and cap if not previously done with the rebuild!
Have sent my early re-linered 4.2 block in for cleaning and
machining but now find I have to choose between two different sets
of rings for my K. Smitt pistons. One set has a 1 piece oil control
with stepped 2nd comp. ring and plain top ring. The other set has a
3 piece oil control with a chrome plated top ring where there is a
warning not to use with high compressions or with an engine likely
to suffer from detonation.I remember that the original spec on a
standard engine included a chrome top ring with the 9.1 comp
ratio,but what is the advantage-disadvantage of a chromed top ring?
Just as an aside, a well known Jag specialist here in UK turned me
down on my request for machining work on the grounds that they
would only do it if they could assemble the whole engine which I
found strange.After spending �7000 on two engines that were built
for me in the past which both failed in a short space of time, one
only went 15 miles,I like to attend this part myself as I don’t
have a budget to work to.–
Keith.P. Series2 Roadster
exmouth, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from sozfingers sent Thu 20 Nov 2008:
Hi Keith,
I’ve seen a fair amount of oil burning with the one piece oil rings
so I won’t use them even if my customer brings in his own new
pistons with rings included. Chrome compression rings are mainly
good for long wear characteristics in an abrasive environment like
a dirt track car with no air cleaner. They are also used in modern
engines that have very thin compression rings, again for better
life. Because they are so hard they require a coarser cylinder
finish in order to get them to seat properly. I think the rings
you’re looking at are cast iron bodied and that is too fragile to
withstand high compression (11:1 and up) or detonation when used as
a top ring. I prefer to use a moly top ring, a stepped second ring,
and a three piece oil ring. For competition engines I use a ductile
iron bodied moly top ring.
Regards,
Rich Olson '67 OTS–
The original message included these comments:
Have sent my early re-linered 4.2 block in for cleaning and
machining but now find I have to choose between two different sets
of rings for my K. Smitt pistons. One set has a 1 piece oil control
with stepped 2nd comp. ring and plain top ring. The other set has a
3 piece oil control with a chrome plated top ring where there is a
warning not to use with high compressions or with an engine likely
to suffer from detonation.I remember that the original spec on a
standard engine included a chrome top ring with the 9.1 comp
ratio,but what is the advantage-disadvantage of a chromed top ring?
In reply to a message from Richard Olson sent Thu 20 Nov 2008:
thanks for clarifying that Richard,I’ve been running through the
search forum and reading various tips on bedding in rings to a new
bore. I remember my dad telling me years ago to load it up at full
throttle but only in the high gears, not letting the revs rise too
high then letting rip after a thousand miles, do you agree with
this technique?–
The original message included these comments:
In reply to a message from sozfingers sent Thu 20 Nov 2008:
Hi Keith,
I’ve seen a fair amount of oil burning with the one piece oil rings
so I won’t use them even if my customer brings in his own new
pistons with rings included. Chrome compression rings are mainly
In reply to a message from sozfingers sent Thu 20 Nov 2008:
Keith : please, please, don’t use full throttle at all during the
running in period, and above all do NOT allow the engine to labour
under heavy throttle openings in the high gears. I don’t know what
this does to piston ring bedding, but I can tell you that it
absolutely wrecks bearings, and is one of the easiest ways
completely to ruin an engine as a long term prospect
I imagine it was VSE that refused to do the machining - I met
with the same refusal, the reason being that they have had some
unfavourable experiences having gone down that road–
christopher storey
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
In reply to a message from sozfingers sent Thu 20 Nov 2008:
The general procedure for seating new rings on a fresh rebore is to
keep the engine in a varying rev range, no lugging and no red
lining. You do want to put the engine under some load, increasing
as the mileage increases.
The trick is that you are trying to wear the particular ring edge
shape and hardness to the particular bore finish. If one wears
smooth before the other then the break-in process stops and you may
get oil burning. When you load the engine the cylinder pressure
forces the top ring into the cylinder to help the break-in. The
worst thing you can do is to put a fresh engine into a parade. That
guarantees an oil burner. Any automotive machinist worth his
micrometer will want to see the rings before he hones the final
finish on the bores. Only then can he provide a compatible surface
that will break-in along with your rings.
Regards,
Rich Olson '67 OTS–
The original message included these comments:
bore. I remember my dad telling me years ago to load it up at full
throttle but only in the high gears, not letting the revs rise too
high then letting rip after a thousand miles, do you agree with
this technique?
In reply to a message from christopher storey sent Fri 21 Nov 2008:
Yep, this is probably why my dads car left a smoke trail everywhere
he drove! I always go very lightfooted on my run-ins but was
intrigued by some comments over the years on this forum where some
have advocated full throttle openings in the early stages as the
only way to bed in the top ring. Picked up the block yesterday,
�260 for the re-bore and block sufacing, rings are coming from
Phoenix I understand where I think the pistons I use are used in
an aero application, on an flat four I believe. Over �800 paid out
yesterday for new valves, springs, head studs and big end
bolts,things have gone up a bit since my last build ten years ago,
but I remember when my car was only 7 years old when a lot of E
spares just were not available,thanks for all those people who
supply what we need, the profits can’t be great.–
The original message included these comments:
In reply to a message from sozfingers sent Thu 20 Nov 2008:
Keith : please, please, don’t use full throttle at all during the
running in period, and above all do NOT allow the engine to labour
under heavy throttle openings in the high gears. I don’t know what
this does to piston ring bedding, but I can tell you that it
absolutely wrecks bearings, and is one of the easiest ways
Exactly what our Sprite’s 1961 factory BMC manual says, Rich.
;]–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.
Richard Olson wrote:
In reply to a message from sozfingers sent Thu 20 Nov 2008:
The general procedure for seating new rings on a fresh rebore is to
keep the engine in a varying rev range, no lugging and no red
lining. You do want to put the engine under some load, increasing
as the mileage increases.
The trick is that you are trying to wear the particular ring edge
shape and hardness to the particular bore finish. If one wears
smooth before the other then the break-in process stops and you may
get oil burning. When you load the engine the cylinder pressure
forces the top ring into the cylinder to help the break-in. The
worst thing you can do is to put a fresh engine into a parade. That
guarantees an oil burner. Any automotive machinist worth his
micrometer will want to see the rings before he hones the final
finish on the bores. Only then can he provide a compatible surface
that will break-in along with your rings.