When you find something is wrong, fix IT. Don’t modify something else to
compensate. I would either mill the underside of the tappets or get the
correct ones.
Unfortunately, we found two surprising things: 1) the
new tappets are all over the place, in terms of thickness, varying
from 0.230’’ to 0.256’’. 2) The old tappets are consistently about
0.020’’ thinner. Several of the valves are already running on
near minimum thickness shims. So, if we put in the new tappets, we
will have negative clearance - not good.
So - What do we do? I can see a number of options, none
attractive: 1) Grind 0.020’’+ off the tops of the new tappets. 2)
Mill 0.020’’+ off the ‘‘pad’’ on the underside of the new tappets 3)
Remove the head, and ‘‘top’’ the valves 4) Remove the head and
install new valves and seats
What’s the ‘‘right’’ thing to do here?
Guys,
Jerry and I are stumped. We’re trying to help a guy with a
Tempero D-type replica adjust his valves. It appears the engine
was simply pulled from the donor car (3.8S) and dropped in the D-
type untouched (well, maybe a ‘‘Krylon’’ rebuild - i.e. - a fresh
coat of black paint.). When we pulled the cams, we found the
tappets were pretty well trashed. So, we had him order all new
cams. We went back tonight to install the new tappets, and shim
the valves. Unfortunately, we found two surprising things: 1) the
new tappets are all over the place, in terms of thickness, varying
from 0.230’’ to 0.256’’. 2) The old tappets are consistently about
0.020’’ thinner. Several of the valves are already running on
near minimum thickness shims. So, if we put in the new tappets, we
will have negative clearance - not good.
So - What do we do? I can see a number of options, none
attractive: 1) Grind 0.020’’+ off the tops of the new tappets. 2)
Mill 0.020’’+ off the ‘‘pad’’ on the underside of the new tappets 3)
Remove the head, and ‘‘top’’ the valves 4) Remove the head and
install new valves and seats
What’s the ‘‘right’’ thing to do here?–
Ray Livingston - '64 OTS Santa Cruz, CA
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
Just as a thought, sometime in the Xk’s production they changed from
long skirt to short skirt tappets - these are the “buckets” we’re
talking about right? I think the change was when the XJ6 came out in 68,
that was when they added valve stem seals.
I’d have to measure, but the XJ6 ones are much shorter than the old ones
that would have come with a 3.8S, so perhaps you could find a good set
of old ones?
Craig
Ray Livingston wrote:
Guys,
Jerry and I are stumped. We’re trying to help a guy with a
Tempero D-type replica adjust his valves. It appears the engine
was simply pulled from the donor car (3.8S) and dropped in the D-
type untouched (well, maybe a ‘‘Krylon’’ rebuild - i.e. - a fresh
coat of black paint.). When we pulled the cams, we found the
tappets were pretty well trashed.
Another option would be to grind the original tappets on top
to clean them up – a much lighter cut would be needed, and
then larger shims would work, too giving more adjustability
in future. Of course we have to worry about the hardening on the
top – how to replace/recreate it.
Jerry
Jerry Mouton '64 E Type FHC “Laissez les bons temps rouler!”
Right – the new ones are shorter-skirted than the originals…
Jerry
Jerry Mouton '64 E Type FHC “Laissez les bons temps rouler!”----- Original Message -----
From: “Craig Talbot” talbotc@telus.net
Just as a thought, sometime in the Xk’s production they changed from
long skirt to short skirt tappets - these are the “buckets” we’re
talking about right? I think the change was when the XJ6 came out in 68,
that was when they added valve stem seals.
I’d have to measure, but the XJ6 ones are much shorter than the old ones
that would have come with a 3.8S, so perhaps you could find a good set
of old ones?
In reply to a message from Craig Talbot sent Fri 11 Jun 2004:
Craig,
The difference you’re talking about is the length of
the ‘‘skirt’’ of the tappet, which is really irrelevent. What I’m
talking about is the thickness of the ‘‘head’’ of the tappet. With
these new one, even with minimum thickness shims, the valves will
no be even close to closed!–
The original message included these comments:
Ray,
Just as a thought, sometime in the Xk’s production they changed from
long skirt to short skirt tappets - these are the ‘‘buckets’’ we’re
talking about right? I think the change was when the XJ6 came out in 68,
that was when they added valve stem seals.
I’d have to measure, but the XJ6 ones are much shorter than the old ones
that would have come with a 3.8S, so perhaps you could find a good set
of old ones?
Craig
–
Ray Livingston - '64 OTS Santa Cruz, CA
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
Are the older tappets thinner than the new ones? I think I have a set of
old one I could be persuaded to part with, if that would work. Let me
know what head thickness you need and I can measure mine tomorrow night.
Craig
Ray Livingston wrote:
In reply to a message from Craig Talbot sent Fri 11 Jun 2004:
Craig,
The difference you’re talking about is the length of
the ‘‘skirt’’ of the tappet, which is really irrelevent. What I’m
talking about is the thickness of the ‘‘head’’ of the tappet. With
these new one, even with minimum thickness shims, the valves will
no be even close to closed!
In reply to a message from Ray Livingston sent Fri 11 Jun 2004:
Ray,
From what I’ve read regarding tappet noise recently on here, I’d
replace all tappets with constant thickness ones, measure the
clearances and remove and top the valve stems by surface grinding
as necessary.
When I got new vlaves for mine (8 years ago), that’s what I had to
do.
You’ve got to be careful that if you use the thinnest shims, or try
to increase the clearance by grinding the shims or the small pad
under the bucket, the shims can fall out of the wells and/or the
spring retainer can touch the underside of the bucket causing all
sorts of risky problems with the collets not being loaded properly.
From your description I would say that the thickness
spread of the new tappets (0.026") sounds alarming.
I have a number of older (longskirted) and newer ones
(shortskirted) in my inventory and I will measure them
for center thickness tomorrow and let you know.
In the Service Manual, Jaguar gives a nominal distance
from the back of the camshaft to the top of the valve stem.
You measure that with the tappets and pads out. If you
are within about 0.005" of that target, your valve and valve
seat are beyond suspicion and when using nominal tappets
you should end up with about 0.085" for the nominal pads.
If you are way out of the target value, it’s head-off time for
new valves, guides and valve seats. Also inspect the cam
bearings. Their condition can affect the clearances too.
Some valve stems have hardened Stellite tips on the stems
and you would not want to grind them. You also run the risk
of the pad now contacting the spring collar instead of the
valve stem. Not recommended unless these are confirmed
non-standard valves with longer tips above the circlip groove.
Do not grind valve stems in-situ, the resulting metal dust will
find its way to the main bearings eventually… you also cannot
expect an accurate angle and finish.
On high mileage engines the valve seat can be pounded in
to the point that you get out of pad range on the low end, but
the measurement method above will rule that in or out.
If the distance is within about 0.005", the problem lays with
the tappets/pads and is a lot easier to solve, at least the head
does not have to come off for that reason.
Dick Vandermeyden
San Carlos, CA________________________________________________________________
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In reply to a message from Mike Eck sent Fri 11 Jun 2004:
Mike,
Agreed, but it could well be the valve stems which are too long -
it’s important to establish what is wrong first. As I said before,
if the stems are indeed too long, and/or the tappets or shims were
relieved, it could lead to the shims falling out of the wells.
Not so long ago, many of the available new Jaguar valves (for older
xk engines) had to be modded slightly to fit properly.
Regards,
Garth.–
The original message included these comments:
When you find something is wrong, fix IT. Don’t modify something else to
In reply to a message from Ray Livingston sent Fri 11 Jun 2004:
Ray
Yhe ‘‘right’’ thing to do is to take the head off & fit new seats &
valves …hardened of course ‘cause the seats have ‘‘retreated’.
What I do is grind down the tappets.Every original one I’ve ever
measured has been 0.223’’ thick so please tell us where the new ones
are from so we can avoid them.Tha famous ‘‘long time Jag mech’c’’
tells me the hardening goes all the way through.The thinnest I’ve
had one is
0.205’’.Then of course you thin the shim if still needed.
One thing that helps is to measure the depth of the fitted stem
from the deck of the head,where the cam cover sits.If you have a
correctly set up head on anothe rcar that helps.Then do the math.
Also you might be better off getting a performance cam.In
replofiling it they cut the back off the lobe .They even sell
thicker shims to fill the gap.Not needed in this case.
Of course afer all this you’re still relying on a head rebuilt by a
guy who set the stem heights all over the place…see first
statement
Hope this helps.
MikeB–
The original message included these comments:
the valves. Unfortunately, we found two surprising things: 1) the
new tappets are all over the place, in terms of thickness, varying
from 0.230’’ to 0.256’’. 2) The old tappets are consistently about
0.020’’ thinner. Several of the valves are already running on
near minimum thickness shims. So, if we put in the new tappets, we
will have negative clearance - not good.
In reply to a message from Ray Livingston sent Fri 11 Jun 2004:
It sounds as if the problem here is the valve has retreated too far
into the seat thereby closing the tappet gap. It could be due to
age (worth pulling the head and correcting) or, if new valves have
been fitted and the seats recut.
Two engine remanufacturers I have spoken to say it is no problem.
All you would do is to grind down the tappet shim. In fact, I am
having my head rebuilt by Classic Torque here in the UK (I believe
he also does work for Rob Beere) and he will supply me with a set
of ground down shims in order for me to set a gap and then send me
a set ground to the correct thickness. I could have new seats
fitted but want to do as little work to an original head as
possible.
In extreme cases (this guy builds �5K plus racing engines) they
will also grind the valve stem down as well.
In reply to a message from Angus Moss sent Fri 11 Jun 2004:
Angus,
You have to be careful there! There’s a reason the minimum
shim thickness is 0.085’’. If you go much thinner than that, the
tappet can end up resting on the spring retainer, rather than the
shim. Start the engine like that, and you stand a real good chance
of swallowing a whole lotta valves, as the cams will be compression
the springs, rather than pushing the valves, allowing the keepers
to pop out.–
Ray Livingston - '64 OTS Santa Cruz, CA
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–