These cams, especially the 5R, were designed to the outer limits of the
valvetrain geometry. On this family of Mitsubishi head designs there is a
limitation of how much valve lift we can achieve while maintaining good
rocker arm to valve tip contact and stability.
Having proper valve stem height is REQUIRED in order to use the 5R cam. This is not an option.
If
you have an OEM head that you KNOW FOR A FACT has never had a valve
grind, does not have aftermarket valves, you are OK. If you have had a
valve grind, or have aftermarket valves, checking stem height and
correcting to factory spec is REQUIRED.
Being slightly higher (up
to .010") than spec is generally OK, the high lift designs favor a stem
height slightly higher over one that is slightly lower, but if the stem
heights are too high HLA travel and proper operation is seriously
compromised.
When the roller is on the cams base circle (valve
closed) we recommend the HLA can be further compressed a MINIMUM of
.060". This allows for the thermal growth in the length of the valve,
especially the exhaust valve. If this clearance is too small, lowering
the valve stem height is necessary by grinding off a small amount of the
stem tip. You cannot just go to town on the stems- there is a limit to
how much you can grind off before the rocker to retainer clearance
becomes a problem, we recommend NO MORE than .010" come off in most
cases.
If the stem height is too low, the rocker arm to stem
contact goes off center at full lift, and rapid stem/rocker and valve
guide wear occurs, if not total high RPM carnage.
The current production rocker arm has a slightly longer pad and is recommended.
If
your rocker arms are galled or worn flat in the center of the valve
contact pad, throw them away and get new ones. Most people NEVER check
these. Do so.
If your valve guides have been replaced, you need
to make sure the guide height has not been increased over factory spec,
otherwise valve seal damage or guide to retainer contact can occur.
It
is amazing how many otherwise reputable machine shops, with high dollar
Serdi, Sunnen, Newen valve seat cutting machines CANNOT GET THESE
SIMPLE SPECIFICATIONS CORRECT. Do not trust them, make them provide you
with measurements of stem height and valve guide height.
For very
high RPM applications we recommend using the early DSM style HLA's
(they have a smaller diameter plunger) and reducing oil pressure to the
HLA oil galley by using the early JDM oil regulator or a restricted
orifice in the oil distribution block. These two items reduce HLA pump
up effects.
Notes about EVO valvetrains-
Due
to the very tall aluminum retainers used by the factory, valve lift
with the factory retainers is limited to ~.445" max otherwise the valve
seal will be damaged by contact with the bottom of the retainer. If you
have had valve guides replaced, be sure they were installed to the
correct protrusion specification. 119 ( EVO8) and 145 (EVO9) series
EXHAUST cams are the same, only the intakes vary due to the special core
required for the MIVEC system.
TECH TIP: Spring upgrade required, will not work with factory retainers. Must
check for coil bind. 11K RPM capable with good springs. Further
increase in upper RPM power. Intended for use with 65+ lb/min turbos.
Works well with header equipped engines. Not intended for use with
factory pistons. While most aftermarket pistons allow for adequate
piston to valve clearance, checking clearance is highly recommended,
especially with oversize valves. Choppy idle, not recommended for
factory ECU's or any ECU that you cannot disable O2 feedback at idle.
Recommend increasing idle RPM to ~1200RPM.
Fits: Mitsubishi Lancer Evolution VIII 2003-2005