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GROOVED TAPPET - SEE PHOTOS

PostPosted: Sun Feb 05, 2006 9:59 pm
by poiuyt
I just added an album called TWIN CAM TAPPET with scans of the grooved
tappet I pulled out of the engine on Saturday. None of the other
tappeta are damaged and the cam lobe is ok.

I'm guessing the tappet was defective because there was no shortage of
oil in the head.

By the way - I wound up removing the gear because I could not get
enough slack to lift the chain off the gear, even though I backed the
adjuster all the way out. Did not give me any problem at all - let's
hope it goes back the same way!

I have the chain wedged in place with a block of wood to keep it on all
of the other gears.

Steve B.

GROOVED TAPPET - SEE PHOTOS

PostPosted: Mon Feb 06, 2006 1:46 am
by "Tim Engel"
"Steve B" <***@***.***> wrote:
(Snip)...
I'm guessing the tappet was defective because
there was no shortage of oil in the head.


Steve,

Wow! That's much more erosion than I was expecting... sorta re-defines
"groove". Trench, maybe. There's a lot of metal missing and it had no
where to go but into the engine. Regardless of how localized the original
damage is found to be, there should be real concern for the collateral
damage all the bits of iron could still do in the future if not removed.

A proper fix should involve an engine tear down and thorough cleaning. All
the oil passages, the hollow parts (cams, crank, etc), the oil pump, the
oil cooler and hoses... everything the circulating oil touches must be
cleaned. Brushed, not just flushed.

It's a leap to assume the tappet is the root cause simply because there was
no shortage of oil. I suspect there's more at work in there than just
friction/wear and I'm not confident that replacing that tappet will correct
the problem. If the valve was replaced, measure it to make sure the
retainer groove wasn't cut too low. If the valve spring was replaced,
measure it's compressed-solid length to make sure it's not too long.
Either of those conditions could cause the spring to go coil-bound before
the cam reaches full-open, and that would put huge loads into the tappet
and cam. Enough to crack the hardened top surface and cause it to flake
out.

The tappets are surface-hardened. If it was an original tappet that had
worked for years, then there's a low probability of it suddenly going soft
and wearing like that. If it was a replacement tappet that was dead soft
(defective), then it could have worn to that point in a short time. Have
an undamaged surface on the tappet checked for hardness. If it's hard,
then you need to be looking for other culprits before you re-assemble the
engine and call it good.

The top of a good tappet should appear smooth/ polished. In the photo,
the tappet's top surface looks "grainy". Like what you would see in the
fractured edge of a broken cast iron part. Is that what it really looks
like? Or am I seeing something else like oil deposits (that doesn't make
sense either). If the thin, case-hardened top surface cracked, flaked out
and exposed the plain cast iron below, then that sub-surface would wear
quickly. Again, in that case you would really want to know where those bits
of hardened surface went. They cannot be left in the engine.


"Steve B" <***@***.***> wrote:
By the way - I wound up removing the gear because I
could not get enough slack to lift the chain off the gear,
even though I backed the adjuster all the way out.

As mentioned before, the idea isn't to remove the chain from the sprocket.
Rather to lift the cam, sprocket and chain up out of the bearing journals as
far as full tensioner slack will allow. Then lift the back end of the cam
higher yet, tilting the cam "tail high" to clear all but the front
bearing cap studs. Then swing the back of the cam toward the center of the
head and lay the cam down at an angle between studs with the sprocket still
meshed with the chain. Pad the stud threads and the head with rags to
protect the cam lobes and bearing journals.

But it's certainly a good procedure to dismantle everything. That for sure
forces the issue of re-timing the cams from scratch, and that's a good
thing.

Tim



----- Original Message -----
From: "Steve B" <***@***.***>
To: <***@***.***>
Sent: Sunday, February 05, 2006 3:58 PM
Subject: [LotusElan.net] GROOVED TAPPET - SEE PHOTOS


I just added an album called TWIN CAM TAPPET with scans of the grooved
tappet I pulled out of the engine on Saturday. None of the other
tappeta are damaged and the cam lobe is ok.

I'm guessing the tappet was defective because there was no shortage of
oil in the head.

By the way - I wound up removing the gear because I could not get
enough slack to lift the chain off the gear, even though I backed the
adjuster all the way out. Did not give me any problem at all - let's
hope it goes back the same way!

I have the chain wedged in place with a block of wood to keep it on all
of the other gears.

GROOVED TAPPET - SEE PHOTOS

PostPosted: Mon Feb 06, 2006 2:21 am
by Lincoln62
I wouldn't panic. The oil filter do it's job and trap that amont of
metal before it gets to the oil galleries. Worth checking the internals
of the oil pump for damage though.

Cheers
Peter
66S2

Tim Engel wrote:

A proper fix should involve an engine tear down and thorough cleaning. All
the oil passages, the hollow parts (cams, crank, etc), the oil pump, the
oil cooler and hoses... everything the circulating oil touches must be
cleaned. Brushed, not just flushed.


GROOVED TAPPET - SEE PHOTOS

PostPosted: Mon Feb 06, 2006 10:10 am
by rgh0
Tim

Just picking up on one of your comments

"The tappets are surface-hardened".

The original Lotus tappets were chilled cast iron and given their
thickness would have been hard all the way through and typically they
crack if major damage occurs. Modern replacements are steel and
normally nitrided to achieve a thin hard surface layer on a more
ductile subsurface.

Given that the tappet has not cracked and yet it has so much damage it
would not surprise me if it was a modern steel replacement that maybe
was not hardened properly.

Rohan

GROOVED TAPPET - SEE PHOTOS

PostPosted: Mon Feb 06, 2006 1:36 pm
by poiuyt
I drove the car close to 100 miles after the tapping started, to get
home, which would explain why the damage was so bad. I suspect if I
was near home when the problem started the damage would not have been
so bad.

The engine has almost 8000 miles since it was rebuilt, and it was
done by a shop that builds these for racing, so I don't believe that
the wrong parts were used. There is no damage on any of the other
tappets and the cam bearings are clean. I intend to change then oil
again after running it for a short time, and look at the tappets on a
regular basis to see if the problem returns.

Steve B.


--- In ***@***.***, "Tim Engel" <[email protected]> wrote:
"Steve B" <[email protected]> wrote:
> (Snip)...
> I'm guessing the tappet was defective because
> there was no shortage of oil in the head.


Steve,

Wow! That's much more erosion than I was expecting... sorta re-
defines

"groove". Trench, maybe. There's a lot of metal missing and it
had no

where to go but into the engine. Regardless of how localized the
original

damage is found to be, there should be real concern for the
collateral

damage all the bits of iron could still do in the future if not
removed.


A proper fix should involve an engine tear down and thorough
cleaning. All

the oil passages, the hollow parts (cams, crank, etc), the oil
pump, the

oil cooler and hoses... everything the circulating oil touches
must be

cleaned. Brushed, not just flushed.

It's a leap to assume the tappet is the root cause simply because
there was

no shortage of oil. I suspect there's more at work in there than
just

friction/wear and I'm not confident that replacing that tappet will
correct

the problem. If the valve was replaced, measure it to make sure
the

retainer groove wasn't cut too low. If the valve spring was
replaced,

measure it's compressed-solid length to make sure it's not too
long.

Either of those conditions could cause the spring to go coil-bound
before

the cam reaches full-open, and that would put huge loads into the
tappet

and cam. Enough to crack the hardened top surface and cause it to
flake

out.

The tappets are surface-hardened. If it was an original tappet
that had

worked for years, then there's a low probability of it suddenly
going soft

and wearing like that. If it was a replacement tappet that was
dead soft

(defective), then it could have worn to that point in a short
time. Have

an undamaged surface on the tappet checked for hardness. If it's
hard,

then you need to be looking for other culprits before you re-
assemble the

engine and call it good.

The top of a good tappet should appear smooth/ polished. In the
photo,

the tappet's top surface looks "grainy". Like what you would see
in the

fractured edge of a broken cast iron part. Is that what it really
looks

like? Or am I seeing something else like oil deposits (that
doesn't make

sense either). If the thin, case-hardened top surface cracked,
flaked out

and exposed the plain cast iron below, then that sub-surface would
wear

quickly. Again, in that case you would really want to know where
those bits

of hardened surface went. They cannot be left in the engine.


"Steve B" <[email protected]> wrote:
> By the way - I wound up removing the gear because I
> could not get enough slack to lift the chain off the gear,
> even though I backed the adjuster all the way out.

As mentioned before, the idea isn't to remove the chain from the
sprocket.

Rather to lift the cam, sprocket and chain up out of the bearing
journals as

far as full tensioner slack will allow. Then lift the back end of
the cam

higher yet, tilting the cam "tail high" to clear all but the
front

bearing cap studs. Then swing the back of the cam toward the
center of the

head and lay the cam down at an angle between studs with the
sprocket still

meshed with the chain. Pad the stud threads and the head with
rags to

protect the cam lobes and bearing journals.

But it's certainly a good procedure to dismantle everything. That
for sure

forces the issue of re-timing the cams from scratch, and that's a
good

thing.

Tim



----- Original Message -----
From: "Steve B" <[email protected]>
To: <***@***.***>
Sent: Sunday, February 05, 2006 3:58 PM
Subject: [LotusElan.net] GROOVED TAPPET - SEE PHOTOS


> I just added an album called TWIN CAM TAPPET with scans of the
grooved

> tappet I pulled out of the engine on Saturday. None of the other
> tappeta are damaged and the cam lobe is ok.
>
> I'm guessing the tappet was defective because there was no
shortage of

> oil in the head.
>
> By the way - I wound up removing the gear because I could not get
> enough slack to lift the chain off the gear, even though I backed
the

> adjuster all the way out. Did not give me any problem at all -
let's

> hope it goes back the same way!
>
> I have the chain wedged in place with a block of wood to keep it
on all

> of the other gears.


GROOVED TAPPET - SEE PHOTOS

PostPosted: Mon Feb 06, 2006 3:12 pm
by Harald S. Feeß
Steve,

could you ask the shop and tell us what they say ?

Harry


The engine has almost 8000 miles since it was rebuilt, and it was
done by a shop that builds these for racing, so I don't believe that
the wrong parts were used. There is no damage on any of the other
tappets and the cam bearings are clean. I intend to change then oil
again after running it for a short time, and look at the tappets on a
regular basis to see if the problem returns.

Steve B.

GROOVED TAPPET - SEE PHOTOS

PostPosted: Mon Feb 06, 2006 6:49 pm
by poiuyt
I'm doing the work myself, but will be in contact with the engine
builder. In fact, I just came back from there with some suggestions:

1. measure from the top of the valve to the deck and compare with the
other valves to check whether the valve has been pushed into the head.
2. Possible broken valve spring
3. 3. chack the bad tappet for out of round causing sticking

What I'll be doing is to chaek the measurements in #1 @ #3 and, if I
can't ID a problem there, replace the tappet with new and see what the
gaps look like. If normal I'll put everything back together and run
the engine. I don't see a down side to this because if the problem
doesn't return I'll chalk it up to a defective tappet. If it returns,
I'll have the head pulled. I don't see any down side to this because
if the problem returns I can then pull the engine apart.

Steve B.


--- In ***@***.***, Harald S. Fee? <[email protected]> wrote:
Steve,

could you ask the shop and tell us what they say ?

Harry


> The engine has almost 8000 miles since it was rebuilt, and it was
> done by a shop that builds these for racing, so I don't believe that
> the wrong parts were used. There is no damage on any of the other
> tappets and the cam bearings are clean. I intend to change then oil
> again after running it for a short time, and look at the tappets on
a

> regular basis to see if the problem returns.

> Steve B.


GROOVED TAPPET - SEE PHOTOS

PostPosted: Mon Feb 06, 2006 10:01 pm
by gwnorth68
I'd like to see the damaged cam bucket? Where is the photo? Sorry for being
obtuse.
Tom Moore

GROOVED TAPPET - SEE PHOTOS

PostPosted: Mon Feb 06, 2006 11:16 pm
by poiuyt
Actually, you sound acute to me!

Look in Twin Cam Tappett in the photo section.

Steve B.

--- In ***@***.***, "tom moore" <[email protected]> wrote:
I'd like to see the damaged cam bucket? Where is the photo? Sorry for
being

obtuse.
Tom Moore