[v12-engine] Which valve is which?

I’m looking over the returned parts from my heads now undergoing rework. Can
someone tell me which is the smaller valve, exhaust or intake? From the
photo in the parts book it looks like the exhaust.

Ed Sowell
'76 XJ-S coupe, red
http://www.efsowell.us/ed/myJag.html

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In reply to a message from Ed Sowell sent Thu 16 May 2013:

The exhaust valve is the smaller one.

If it is all still in pieces, then I’m surprised you didn’t label
them 1-24 before stripdown. If they are already back in place, you
can easily trace the path from the inlet port (or the exhaust port)
on the head back to the relevant valve. The order front to back
goes EIEIEI IEIEIE (as old Macdonald would have said).

kind regards
Marek–
MarekH
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Thanks, Marek.

The work is being done by JP’s European Auto in Huntington Beach. The
machinist etched each set with numbers 0, 2, 3,… 11, 12, where I assume he
used 0 instead of 1 for some reason. That tell me which is which.

I went down and saw the reassembled heads a couple days ago and went over
the work with the shop owner. I was surprised to hear that the seats were
not replaced. The next day I called him and said I was concerned about the
seats, even though they all looked good according to the machinist. He
immediately conceded and sent them back for rework.

But, frankly, I’m amazed at how good the returned valves look, for the most
part. All the intakes look like new, at least to my untrained eye. The
exhausts look pretty good too, with the exception of A4 and A6 which are
seriously corroded on the stem guide surface. The associated springs,
especially A4, are also corroded. I’m trying to put together a theory on how
that could have happened.

Ed Sowell
'76 XJ-S coupe, red
http://www.efsowell.us/ed/myJag.html

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In reply to a message from Ed Sowell sent Thu 16 May 2013:

Ed
Did you have problems removing the heads?
Hayden
78 XJS–
hudge
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In reply to a message from Ed Sowell sent Thu 16 May 2013:

Ed, I’ve enjoyed your posts and look up to you as a
knowledgeable person on V12 & XJ-S matters. Your various
photos and projects are very useful and you’re obviously
very familiar with many aspects of your car through the
long term ownership and improvements etc.

Which is why I’m in mild shock at your initial question
and thread title. I thought it was going to be some kind
of mix up about pressure relief versus filter bypass
valves or something, which could take a bit of head
scratching as the terms are sometimes muddled. There may
be a 4-stroke engine somewhere in a lawn mower or weed
eater, or maybe back in the 19th Century or early 20th
that had equal sized valves - I don’t know. But asking
which is the larger valve struck me almost like mixing up
the big and little end of a connecting rod. Not quite, but
almost…

My main point though is that if an experienced machinist
who I assume has done lots of engines says the seats look
OK where’s the problem? If you didn’t know which valve was
which (no offence) why would you be anything other than
happy, reassured in fact, that the pro was denying himself
some easy extra income and doing the right thing by his
customer?

I had an overdrive rebuilt one time by ex-Laycock
personnel who assured me I needn’t spend the extra money
on a competition upgrade just because I wanted to use it
in a V12 E-type. Being stupid, I mumbled something about
maybe using it in something else later and would they do
the upgrade anyhow? Like your machinist, they ‘immediately
conceded’ but I was very impressed that they did not seek
to extract maximum revenue from me until I practically
insisted.

Many times in life it’s the poor old customer who gets
ripped-off by the savvy pro padding extra work onto the
bill. In the case of my overdrive it needed doing anyhow
and there was no downside or pointless machining required,
just alternative parts and assembly. In your case, you are
gouging out original factory metal and incurring serious
extra expense whilst trusting the result to be better than
stock. If the guy is good it might even be so, but if he’s
good why question his initial opinion if you’re not
familiar enough to be able to ID valves?

Anyway, keep up the good work…

Pete–
The original message included these comments:

I went down and saw the reassembled heads a couple days ago and went over
the work with the shop owner. I was surprised to hear that the seats were
not replaced. The next day I called him and said I was concerned about the
seats, even though they all looked good according to the machinist. He


1E75339 66 D, 885958 62 FHC,1R27190+1R28009 70FHCs, 1960 Mk9
Gaithersburg, Maryland, United States
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Hi Pete,

Thanks for your frank input.

I did feel a bit silly at not knowing which valve was which, but frankly I
don’t see how that lack of knowledge translates into not being qualified to
question the shops decisions on replace vs not of parts that I am paying $3k
to get close enough to even consider the matter.

What meager, practical knowledge of auto engines I do have I got from high
school auto shop or gleaned from these forums, Jag Club members, etc. On the
matter of the keeping or replacing the valve seats the vote from the latter
sources is about 50/50. I’m leaning towards not replacing them, on the
grounds you mention.

Then there is the matter of the guides. The machinist replaced the intake
guides only, in spite of the obvious serious corrosion on the stems of two
exhaust valve stems. IMHO, if the stems are corroded, how could the guides
not be?

Then there’s the matter of the root cause of the problem. The shop nor the
machinist seem to believe it’s necessary to go further than saying “oil
starvation” and cleaning the feed lines and cam bores (actually, the right
cam itself will be replaced). No one, including this forum, has offered an
explanation of the absolutely dry, rusty, and collapsed exhaust springs on
A4 and A6. Here’s mine: I believe it’s because they have been running so hot
as to vaporize any oil that happens to splash their way. I believe this is
because those valves have not been closing. Going way out on the limb, I
speculate that the overheating also reached the camshaft, possibly
vaporizing oil in the bore. As bizarre as that seems, if true it would
explain the loss of lubrication forward and all that wear on the guides.

Ed Sowell
'76 XJ-S coupe, red
http://www.efsowell.us/ed/myJag.html

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Ed
Did you have problems removing the heads?
Hayden

No, I didn’t. The tech that actually did it didn’t have much difficulty. The
shop had a heavy-duty looking pulling plate setup.

Ed Sowell
'76 XJ-S coupe, red
http://www.efsowell.us/ed/myJag.html

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In reply to a message from Ed Sowell sent Mon 20 May 2013:

Thanks for taking my query in the spirit it was intended
Ed. Are you saying there’s a fixed $3k bill in prospect
and he was then deciding how much to do? I’d have thought
the cost would go up or down with actual work needed,
after an up-front cleaning/checking charge of course.

Depending on material a valve and guide can corrode
differently or not at all. Valves (including new ones) are
very easy to measure. Guides slightly less so but if he
has visually inspected and accurately measured them it’s
not a given they need replacing on a lowish miles/lowish
use engine although for many shops it might be a default
fixed-price refurb SOP.

Any new guides must have resulted in recut seats for those
valves. Hope he didn’t overdo it.

I don’t remember the valve or spring issue but do not
believe vaporisation is a feasible cause for parts running
in an oil bath. Of course lack of lube and excess heat go
hand in hand - either from excess friction or lack of
bathing and heat removal, so there could be an element of
chicken and egg guesstimation.

I don’t know if he’s a good machinist or not, plus not
every good machinist is a first class diagnostician and
vice versa.

Good luck

Pete–
1E75339 66 D, 885958 62 FHC,1R27190+1R28009 70FHCs, 1960 Mk9
Gaithersburg, Maryland, United States
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In reply to a message from PeterCrespin sent Mon 20 May 2013:

I think it was a perfectly reasonable question and anyone who will
do their own valve timing will ask exactly the same.

I answered it the way I did because the order changes between
cylinders 1-3 and 4-6 and with others in mind, putting this
down ‘‘on paper’’ and into the archive, with an easily understood
question and equally easily understood answer can only stand
someone else in good stead at some future date, assuming they know
what the button labelled ‘‘Search Forums’’ means.

Before the next person asks, it is the same for HE and pre-HE and
if you have an HE, this is where the phrase ‘‘pocketed exhaust
valve’’ starts to make sense.

To test your theory Ed, it would have been interesting to have
known what shim thicknesses and valve clearances you had at
stripdown.

My money would still be on an oil blockage at the pipe to the cam.
I’d guess that as the compartments along the cam are linked, so if
any oil were getting up there, then there ought to have been oil
all along the cam before it got to drain down to the sump. At
startup, there ought to be (cold) oil at ~10psi gushing out of the
cam caps within seconds of startup, which can only get better as it
all heats up and the oil thins, yet you have reported ‘‘oil
stavation’’. I say that based on looking at an open cam fed by an
insecticide sprayer when pre-oiling the engine whilst doing valve
timing.

Ask yourself, why did the other cam not suffer the same fate, since
its valve timing was unlikely to be any different?

kind regards
Marek–
MarekH
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Hi Pete,

Are you
saying there’s a fixed $3k bill in prospect and he was then deciding how
much to do? I’d have thought the cost would go up or down with actual
work needed, after an up-front cleaning/checking charge of course.

I got estimates from 4 shops. The two most reasonable one, bot highly
regarded, quoted 30 hours for R/R of the heads. Also both quoted about $1000
for rebuilding the heads or exchange for rebuilt ones, once shipping charges
were factored in. One would have done complete replacement of everything,
the other, which was the shop I chose to do the work, was to replace what
needed replacement.

Depending on material a valve and guide can corrode differently or not at
all. Valves (including new ones) are very easy to measure. Guides
slightly less so but if he has visually inspected and accurately measured
them it’s not a given they need replacing on a lowish miles/lowish use
engine although for many shops it might be a default fixed-price refurb
SOP.

One thing I didn’t mention before is the end of the A4 exhaust stem had been
damaged. There was a bit of mushroom, enough so that it would not easily
slip into one of the intake guides that were removed. So my guess is the A4
exhaust guide was scored when the valve was removed. The cost of the part
and R/R of a guide can’t be all that much, so in my view it should be
replaced.

So what I was trying to say was I have already agreed to pay to $3k to R/R
the heads. The Jag shops seem to be giving 12 month/12k mile warranty these
days, but I hope to drive the car another 10 years or so and would really,
really hate to have to do pay another $3 again in 5 years to fix a dropped
seat or a sticky valve guide.

I don’t remember the valve or spring issue

The photo album is now at my website. Click on link below, then go to bottom
of page and click on Valve Train Problem.

but do not believe
vaporisation is a feasible cause for parts running in an oil bath. Of
course lack of lube and excess heat go hand in hand - either from excess
friction or lack of bathing and heat removal, so there could be an
element of chicken and egg guesstimation.

Can you think of a better explanation for only 2 of the 12 valves on the
A-bank to be dry and corroded? If it was friction, presumably it would be in
the guides and/or tappets. The worst guide wear was near the front, where
the springs were not dry and corroded. I would very much like to understand
why that would be.

Again, thanks for your interest and your thoughts.

Ed Sowell
'76 XJ-S coupe, red
http://www.efsowell.us/ed/myJag.html

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In reply to a message from Ed Sowell sent Mon 20 May 2013:

Frankly Ed, I’m struggling with the very idea of dry and
corroded valve gear on any car engine with enclosed cams
and valved. Last time I saw anything vaguely in that line
it was the exposed sidevalve gear on an air-cooled WW2
Norton single I had. Oil starvation has to be the #1
suspect.

Pete–
1E75339 66 D, 885958 62 FHC,1R27190+1R28009 70FHCs, 1960 Mk9
Gaithersburg, Maryland, United States
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One thing I didn’t mention before is the end of the A4 exhaust stem
had been damaged. There was a bit of mushroom, enough so that it would
not easily slip into one of the intake guides that were removed.

That’s unusual. Offhand, I can only think of three possible reasons
for such damage:

  1. That particular valve was defective, not heat-treated properly.

  2. Somebody had been in there before, and when they discovered that
    the clearance wasn’t quite right, they fixed it by grinding off the
    tip of the stem – which breaks through the case hardening and
    exposes softer metal within.

  3. Something prevented that valve from opening, so the cam had to
    push on it really hard.

Anybody else have other ideas?

– Kirbert

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !On 20 May 2013 at 14:44, Ed Sowell wrote:

Thanks, Kirby.

That’s unusual. Offhand, I can only think of three possible reasons for
such damage:

  1. That particular valve was defective, not heat-treated properly.

I had thought about that. My records of compression tests show A4 low
(70psi) on and off since at least late '90s, so the valve issue is not a
sudden, recent development.

  1. Somebody had been in there before, and when they discovered that the
    clearance wasn’t quite right, they fixed it by grinding off the tip of
    the stem – which breaks through the case hardening and exposes softer
    metal within.

This engine has never been opened before. I’ve owned it since late 1980 and
got all service records.

  1. Something prevented that valve from opening, so the cam had to push
    on it really hard.

There is evidence of that, in my opinion. E.g., the cam lobe was worn, and
the noise which caused me to have the heads pulled.

BTW, have you looked at the photos? I would really like your opinion (as
well as others’ here) on the bone dry, rusty, collapsed springs.

Ed Sowell
'76 XJ-S coupe, red
http://www.efsowell.us/ed/myJag.html

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In reply to a message from Ed Sowell sent Tue 21 May 2013:

I have never in my life seen guide wear like that, or even close.
No wonder you had a noise and low compression. Can’t think what
happened except either total lack of lube over a long period or
some kind of water leakage through a porous casting or something?

By the way, in case it’s any use to you, I have a set of 18,000
mile liners, rods and pistons plus crank and sundry other bits,
including cams. They came from an XJ-S engine like yours that got
damaged in a crash and stripped for parts. The postage would be
high but other than that pm me off list if it’s still relevant. I
only thought of them when I looked up your photos, in case one or
two of your cylinders are dud after that kind of punishment?

Pete–
1E75339 66 D, 885958 62 FHC,1R27190+1R28009 70FHCs, 1960 Mk9
Gaithersburg, Maryland, United States
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In reply to a message from PeterCrespin sent Tue 21 May 2013:

Ed,

I have looked at the photos and was wondering how long between you
stopped driving and the photo of the rusty spring still in place on
the head?

Dan–
DanS
columbus ga. usa, United States
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Dan,

I have looked at the photos and was wondering how long between you
stopped driving and the photo of the rusty spring still in place on the
head?

Not very long. It had been getting noisier and noisier and when I finally
decided on the shop to take it to I had it flat-bedded there. So it sat in
my garage about 2 weeks, but I drove it up onto the flat-bed.

Ed Sowell
'76 XJ-S coupe, red
http://www.efsowell.us/ed/myJag.html

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In reply to a message from Ed Sowell sent Tue 21 May 2013:

Ed
I expect you may have thought of this, but in case not:
Once the head is reassembled but still off the engine, would
it be possible for your garage to rig up a methos of
pressurising some oil through the banjo on that side, while
turning the cam, so you can see what happens to the oil?

Or even, do this before the valves are inserted with the cam
in place only?–
HE V12
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Thanks, Jean. Someone here described such a process, done with the heads in
place. He put oil in at garden pesticide sprayer and jury-rigged a
connection to the distribution tower, then watched the flow along the cams.
I tried to get the shop to do this but they pointed out that they have
cleaned and verified as clear all the feed lines and cam center bore, and
maintain that should be proof enough. I had to agree.

Ed Sowell
'76 XJ-S coupe, red
http://www.efsowell.us/ed/myJag.html

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In reply to a message from Ed Sowell sent Wed 22 May 2013:

Ed, it’s ok to believe the machine shop, but I heartily reccomend
the pesticide sprayer to pressurize the oil system before you re-
install the cam covers.
I would really like to see proper oil delivery to that cam lobe.

BTW, were the cam bearings in this area OK?

Mark.–
The original message included these comments:

place. He put oil in at garden pesticide sprayer and jury-rigged a
connection to the distribution tower, then watched the flow along the cams.


Mark Mackay 1974 E Type OTS 5 speed
Park City, UT, United States
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Thanks, Mark.

Ed, it’s ok to believe the machine shop, but I heartily reccomend the
pesticide sprayer to pressurize the oil system before you re- install the
cam covers.
I would really like to see proper oil delivery to that cam lobe.

BTW, were the cam bearings in this area OK?

I’ll have another go at him on the testing issue.

The shop made the judgment to replace both the cam and the tower (tappet
block) due to excessive wear. I have these parts and was able to measure the
wear on the A6 exhaust lobe, but since they didn’t give me the journal caps
I could measure the journals. As you know, there are no inserts on the V12.

Ed Sowell
'76 XJ-S coupe, red
http://www.efsowell.us/ed/myJag.html

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