help documents for valve adjustment job?
Discussion
Here's a very detailed how-to from Tim Engel:
The manual covers the basic steps fairly well but doesn't get into details.
With the timing belt off, turn the crank back from TDC 90°. That puts all the
pistons half way down their bores and out of harm's way with regards to
hitting the valves. With stock cams, the intake and exhaust valves will
not collide with each other, so with the pistons down out of the way, you
are free to spin the cams as will. Use a 17 mm wrench or socket on the hex
of the pulley-securing bolt to turn the cams easily.
The valve clearances tend to tighten up with wear (the valve head hammers
it's way up into the valve seat, the end of the valve stem gets closer to
the cam, and the clearances get tighter). So shooting for the high end of
the clearance range will optimize the time it will take for clearances to
reach minimums again (how often do you wish to repeat this). The ranges
are .005" to .007" for intakes and .010" to .012" for exhaust, so shoot
for .007" IN and .012" EX.
Measure the existing clearances and the installed shim thicknesses.
Calculate how much more or less clearance is required and select a thicker
or thinner shim as required.
I use a worksheet with two rows of circles drawn on it. One row for each
of the two cams. Each row has four sets of two circles side by side for
the tappets. Above each circle I write the measured clearance and shim
thickness in the engine as well as the calculated shim thickness required.
Then as the required new shims are found in your stash (including those
currently elsewhere in the engine) or purchased, place them in the circles.
When you get ready for the next trial assembly, just transfer the shims
from the worksheet to the engine.
I've put an MS-Excel worksheet in the Files section. Scroll way down to
the Tech folder and open it, then open the Engine folder and look for "9xx
Valve Shim Worksheet - Shop Format.xls. Enter the current clearance and
shim measurements in the appropriate fields. It will calculate the
required shim thickness to produce valve clearances at the tops of each
range (0.012" for exhaust and .007" for intake). When you print it out,
it will have the circle pattern described above as well as the measured and
required dimensions.
Note that all sealants have thickness, even the so-called zero-clearance
sealants. If you shim the valves to perfection at the top of the range
when everything is assembled dry, then when you add the sealant the carrier
and it's cam will be lifted some small amount higher above the head and
valves, resulting in more valve clearance. The old Loctite 504 would add
about 0.0015" to the clearance. I think Loctite 524 and Permatex Aviation
Form-A-Gasket add something less than 0.001", and Loctite/ Permatex 518 and
Permabond A136 add 0.0005" (half a thousandth). The latter is not enough
to worry about, but 0.0015" would be worth allowing for. Just shim the
valves tighter than your target by the expected sealant thickness and count
on it to open the clearances the last little bit during final assembly.
New shims are flat on both sides and it doesn't matter which way they are
installed... there is no up or down. However, used shims can develop a
small circular depression in the center where the end of the valve stem
rides. Sometimes it's little more than a bright spot, other times it will
be deep enough to feel with your fingernail. Measuring the shim thickness
at the rim and at the center will give two different results, and depending
how the shim is installed, it will two different working thicknesses.
The inside of the tappet has a flat surface that contacts the shim that is
wide enough to bridge across the depression... it won't touch the floor of
the depression. So with the depression facing up into the tappet, the
shims rim thickness is it's working thickness. If you flip the shim over
so the depression faces the valve stem, the top of the stem will contact
the lower level of the depression and the shim's center thickness is it's
working thickness. Use a micrometer to measure shim thickness since you
can place the small diameter anvil just where you want to check the
thickness. The jaws of a caliper will not get into the center depression
to check the thickness there.
If the shim has been used multiple times and has a depression on both sides,
it's best to replace it... they're cheap. The working thickness will be
from the flat rim on one side to the center depression on the other side,
and neither a micrometer nor a caliper will give you that measurement. A
depth gauge and surface plate (ground plate glass isn't bad) and a dial
indicator could measure them correctly, but it's hardly worth the effort or
brain overload. Just buy new shims.
The cup surrounding the end of the valve stem into which the shim sits has a
radiused corner where the side walls meet the bottom. The shims have
square corners. The square and rounded corners would interfere except that
the shim's OD is significantly normally smaller than the cup's ID... a
loose sloppy fit that keeps it from making contact with the radius.
However, I have received some shims from USA suppliers that supposedly came
from LCU that were larger in diameter... a snug fit into the cup. That
put the shim's square edge on the cup's corner radius and the shim would not
sit down against the valve stem properly. After much frustration, I
finally figured out what was going on and ground a corner radius around the
shim's perimeter. That allowed the shim to sit down into the cup properly
and everything was fine. So if the shim is a snug diameter fit into the
cup, expect problems and deal with the before they occur.
Are you taking the opportunity to set the cam's MOP to 104° ? It will
never be easier to do than now. The 110°/100° MOP timing is for emissions,
and the 104° MOP is the cam's nominal design setting. The engine will run
a little better if you set it there. The stock Auxiliary pulley is a 104°
MOP, so just swap it with one of the cam pulleys and purchase a second 104°
pulley for the other cam.
Regards,
Tim Engel
The manual covers the basic steps fairly well but doesn't get into details.
With the timing belt off, turn the crank back from TDC 90°. That puts all the
pistons half way down their bores and out of harm's way with regards to
hitting the valves. With stock cams, the intake and exhaust valves will
not collide with each other, so with the pistons down out of the way, you
are free to spin the cams as will. Use a 17 mm wrench or socket on the hex
of the pulley-securing bolt to turn the cams easily.
The valve clearances tend to tighten up with wear (the valve head hammers
it's way up into the valve seat, the end of the valve stem gets closer to
the cam, and the clearances get tighter). So shooting for the high end of
the clearance range will optimize the time it will take for clearances to
reach minimums again (how often do you wish to repeat this). The ranges
are .005" to .007" for intakes and .010" to .012" for exhaust, so shoot
for .007" IN and .012" EX.
Measure the existing clearances and the installed shim thicknesses.
Calculate how much more or less clearance is required and select a thicker
or thinner shim as required.
I use a worksheet with two rows of circles drawn on it. One row for each
of the two cams. Each row has four sets of two circles side by side for
the tappets. Above each circle I write the measured clearance and shim
thickness in the engine as well as the calculated shim thickness required.
Then as the required new shims are found in your stash (including those
currently elsewhere in the engine) or purchased, place them in the circles.
When you get ready for the next trial assembly, just transfer the shims
from the worksheet to the engine.
I've put an MS-Excel worksheet in the Files section. Scroll way down to
the Tech folder and open it, then open the Engine folder and look for "9xx
Valve Shim Worksheet - Shop Format.xls. Enter the current clearance and
shim measurements in the appropriate fields. It will calculate the
required shim thickness to produce valve clearances at the tops of each
range (0.012" for exhaust and .007" for intake). When you print it out,
it will have the circle pattern described above as well as the measured and
required dimensions.
Note that all sealants have thickness, even the so-called zero-clearance
sealants. If you shim the valves to perfection at the top of the range
when everything is assembled dry, then when you add the sealant the carrier
and it's cam will be lifted some small amount higher above the head and
valves, resulting in more valve clearance. The old Loctite 504 would add
about 0.0015" to the clearance. I think Loctite 524 and Permatex Aviation
Form-A-Gasket add something less than 0.001", and Loctite/ Permatex 518 and
Permabond A136 add 0.0005" (half a thousandth). The latter is not enough
to worry about, but 0.0015" would be worth allowing for. Just shim the
valves tighter than your target by the expected sealant thickness and count
on it to open the clearances the last little bit during final assembly.
New shims are flat on both sides and it doesn't matter which way they are
installed... there is no up or down. However, used shims can develop a
small circular depression in the center where the end of the valve stem
rides. Sometimes it's little more than a bright spot, other times it will
be deep enough to feel with your fingernail. Measuring the shim thickness
at the rim and at the center will give two different results, and depending
how the shim is installed, it will two different working thicknesses.
The inside of the tappet has a flat surface that contacts the shim that is
wide enough to bridge across the depression... it won't touch the floor of
the depression. So with the depression facing up into the tappet, the
shims rim thickness is it's working thickness. If you flip the shim over
so the depression faces the valve stem, the top of the stem will contact
the lower level of the depression and the shim's center thickness is it's
working thickness. Use a micrometer to measure shim thickness since you
can place the small diameter anvil just where you want to check the
thickness. The jaws of a caliper will not get into the center depression
to check the thickness there.
If the shim has been used multiple times and has a depression on both sides,
it's best to replace it... they're cheap. The working thickness will be
from the flat rim on one side to the center depression on the other side,
and neither a micrometer nor a caliper will give you that measurement. A
depth gauge and surface plate (ground plate glass isn't bad) and a dial
indicator could measure them correctly, but it's hardly worth the effort or
brain overload. Just buy new shims.
The cup surrounding the end of the valve stem into which the shim sits has a
radiused corner where the side walls meet the bottom. The shims have
square corners. The square and rounded corners would interfere except that
the shim's OD is significantly normally smaller than the cup's ID... a
loose sloppy fit that keeps it from making contact with the radius.
However, I have received some shims from USA suppliers that supposedly came
from LCU that were larger in diameter... a snug fit into the cup. That
put the shim's square edge on the cup's corner radius and the shim would not
sit down against the valve stem properly. After much frustration, I
finally figured out what was going on and ground a corner radius around the
shim's perimeter. That allowed the shim to sit down into the cup properly
and everything was fine. So if the shim is a snug diameter fit into the
cup, expect problems and deal with the before they occur.
Are you taking the opportunity to set the cam's MOP to 104° ? It will
never be easier to do than now. The 110°/100° MOP timing is for emissions,
and the 104° MOP is the cam's nominal design setting. The engine will run
a little better if you set it there. The stock Auxiliary pulley is a 104°
MOP, so just swap it with one of the cam pulleys and purchase a second 104°
pulley for the other cam.
Regards,
Tim Engel
many thanks. i knew there must be a procedural out there. i could use more detail as the only valve job i've done was on a motorcycle. i've never seen anything like the lotus tappets. does anyone have some general advice and tips for someone opening up the 910 engine for the first time?
Put magnets on each tappet before removing the cam towers, or you will lose all the shims.
Turn the crank back 90deg before moving the cams without the belt on, this will keep you from bending valves on the pistons.
If you are removing the head, DO NOT turn the crank without using cylinder liner holders or you will break the sealant and the cylinders will leak coolant into the sump.
You must tighten the cam tower bolts in the correct order (sorry I don't have the manual on me right now). Also the cam towers are held on by two hex nuts (one on each end) and a bunch of Torx E-10 bolts (need an E-10 socket that can pass through the holes in the cam tower) Use a ratchet and extension with a long jack handle (over the ratchet handle) as a cheater. Support the ratchet with one hand to keep from rounding off the torx, and use the other hand to gently loosen the bolts by gently, and slowly, pushing on the end of the long cheater tube. If you don't do this, you will break or round off the torx, and then they will have to be drilled out.
Turn the crank back 90deg before moving the cams without the belt on, this will keep you from bending valves on the pistons.
If you are removing the head, DO NOT turn the crank without using cylinder liner holders or you will break the sealant and the cylinders will leak coolant into the sump.
You must tighten the cam tower bolts in the correct order (sorry I don't have the manual on me right now). Also the cam towers are held on by two hex nuts (one on each end) and a bunch of Torx E-10 bolts (need an E-10 socket that can pass through the holes in the cam tower) Use a ratchet and extension with a long jack handle (over the ratchet handle) as a cheater. Support the ratchet with one hand to keep from rounding off the torx, and use the other hand to gently loosen the bolts by gently, and slowly, pushing on the end of the long cheater tube. If you don't do this, you will break or round off the torx, and then they will have to be drilled out.
I've got an Excel file that will do the math for you. It's posted on the turboesprit mailing list at YahooGroups, or I can forward it to you as a file attachment. PM me if you want it sent.
Magnets are nice if you have them, but not absolutely necessary. If you pull the cam carrier straight up and hold it there, it's likely that either a shim or two will fall out, or tappets will begin dropping out. Neither is a good thing.
However if you remove the carrier with a rolling motion... rolling it toward you as soon as it clears the studs, and then holding it inverted, there's little risk of loosing a shim.
But magnets are still good.
The usual problem with the Torx bolts isn't really the bolt's fault. The Permabond A-136 sealant (anaerobic sealant like Loctite 515/ 518/ 574) is also a pretty good glue/ threadlocker. If a little too much is applied to the joint, the excess oozes up the bolt/stud hole in the cam carrier. There is sets up and glues the whole mess together.
Then it can take a lot of torque to break a bolt loose. Enough to potentially round-off the drive or to pop the bolt head off.
The obvious solution is to not put on excessive sealant. Also lightly oil the shank of the bolt (not the tread) so it's less likely to stick if sealant does get on it. Be very careful with the oil. Don't get it on any surface that must seal.
In addition to that, the redundant back-up is to replace all the OEM bolts (not very strong) with ARP bolts from JAE. They are very strong and will put up with the abuse required to remove them if you ever glue them in again.
Good luck,
Tim Engel
Lotus Owners Oftha North
>> Edited by Esprit2 on Friday 31st March 03:07
Magnets are nice if you have them, but not absolutely necessary. If you pull the cam carrier straight up and hold it there, it's likely that either a shim or two will fall out, or tappets will begin dropping out. Neither is a good thing.
However if you remove the carrier with a rolling motion... rolling it toward you as soon as it clears the studs, and then holding it inverted, there's little risk of loosing a shim.
But magnets are still good.
The usual problem with the Torx bolts isn't really the bolt's fault. The Permabond A-136 sealant (anaerobic sealant like Loctite 515/ 518/ 574) is also a pretty good glue/ threadlocker. If a little too much is applied to the joint, the excess oozes up the bolt/stud hole in the cam carrier. There is sets up and glues the whole mess together.
Then it can take a lot of torque to break a bolt loose. Enough to potentially round-off the drive or to pop the bolt head off.
The obvious solution is to not put on excessive sealant. Also lightly oil the shank of the bolt (not the tread) so it's less likely to stick if sealant does get on it. Be very careful with the oil. Don't get it on any surface that must seal.
In addition to that, the redundant back-up is to replace all the OEM bolts (not very strong) with ARP bolts from JAE. They are very strong and will put up with the abuse required to remove them if you ever glue them in again.
Good luck,
Tim Engel
Lotus Owners Oftha North
>> Edited by Esprit2 on Friday 31st March 03:07
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