A choice was made between two similar hydraulic roller cams for a mild TPI combo
the crower cam I suggested
http://www.lunaticams.com/Product.aspx?id=1835&gid=254
http://garage.grumpysperformance.com/index.php?threads/port-speeds-and-area.333/
the lunati that was purchased / bought
this will be very informative, because it points out the difference between listed and true lift and duration, look at the duration and lift figures, then at the .050 timing
look both over carefully and compare
most guys use the terms LSA and LCA almost interchangeably WHICH THEY ARE NOT in all cases!
LCA =(LOBE CENTER ANGLES)remember lobe center angles can be changed thru indexing the cam when degreeing it in, LSA (LOBE SEPERATION ANGLE) is ground into the cam during its manufacturing process.
most guys looking at the stated info,
and not the actual timing figures
will think the
LUNATI with its Duration @ .050
Intake:206/Exhaust:215
is slightly wilder than
the CROWER
with its Duration at .050" of
Intake: 204 Exhaust: 213
THATS NOT TRUE
LOOK CLOSELY
LUNATI INTAKE Opens: -5.0 ATDC
Closes: 31.0 ABDC
EXHAUST Opens: 43.5.0 BBDC
Closes: -8.5.0 BTDC
Gross Valve Lift (Int/Exh): .469/.489
CROWER INTAKE Opens: -8.0 ATDC
Closes: 32.0 ABDC
EXHAUST Opens: 45.0 BBDC
Closes: -12.0 BTDC
Lift: .484 Lift: .505
the fact is the crower design is just a bit more aggressive
NEITHER cam is a max effort design. both are designed for a boost over stock but they will retain decent street and traffic manors in basically stock or mildly modified engines, BOTH cams will work fine, in most TPI engine combos if clearances are carefully checked and maintained, and Ill be the first guy to suggest that on a stock set of heads the lunati with its lower lift is the safer choice, but on decent aftermarket heads with no clearance issues the crower design is almost sure to produce a better power curve.
Ive used several very similar cams over the years and every last one in that duration range ran better , in a TPI equipped engine with its restrictive intake, and head flow rates if the cam was retarded a few degrees (INSTALLED SPLIT OVERLAP)vs installed advanced 4 degrees (DOT-TO-DOT)the main reason seems to be that a TPI needs all the upper rpm savaging it can get to help fill the cylinders and with the limited duration the delayed intake valve closing tends to help just a bit to extend the rpm band, higher.
as IM sure your aware
the formula for hp is tq x rpm/5252
lets say the cam change moves the tq peak 150 rpm higher (WHICH IT TENDS TO)
now lets assume the torque peaks at only the same point and power peaks at
http://www.stingray.nu/tips/tech85.htm
165 NET HP @ 5200 the stock engine was supposed to make at 200rpm, higher, but it now jumps just a bit to 5350rpm,thats about 5-6 hp advantage, but in reality youll see closer to 40-60 more hp more due too both the more aggressive cam timing and the slightly retarded timing also, install it advanced and youll still get a big boost but your leaving 3-6 hp on the table in most cases
the crower cam I suggested
http://www.lunaticams.com/Product.aspx?id=1835&gid=254
http://garage.grumpysperformance.com/index.php?threads/port-speeds-and-area.333/
the lunati that was purchased / bought
this will be very informative, because it points out the difference between listed and true lift and duration, look at the duration and lift figures, then at the .050 timing
look both over carefully and compare
most guys use the terms LSA and LCA almost interchangeably WHICH THEY ARE NOT in all cases!
LCA =(LOBE CENTER ANGLES)remember lobe center angles can be changed thru indexing the cam when degreeing it in, LSA (LOBE SEPERATION ANGLE) is ground into the cam during its manufacturing process.
most guys looking at the stated info,
and not the actual timing figures
will think the
LUNATI with its Duration @ .050
Intake:206/Exhaust:215
is slightly wilder than
the CROWER
with its Duration at .050" of
Intake: 204 Exhaust: 213
THATS NOT TRUE
LOOK CLOSELY
LUNATI INTAKE Opens: -5.0 ATDC
Closes: 31.0 ABDC
EXHAUST Opens: 43.5.0 BBDC
Closes: -8.5.0 BTDC
Gross Valve Lift (Int/Exh): .469/.489
CROWER INTAKE Opens: -8.0 ATDC
Closes: 32.0 ABDC
EXHAUST Opens: 45.0 BBDC
Closes: -12.0 BTDC
Lift: .484 Lift: .505
the fact is the crower design is just a bit more aggressive
NEITHER cam is a max effort design. both are designed for a boost over stock but they will retain decent street and traffic manors in basically stock or mildly modified engines, BOTH cams will work fine, in most TPI engine combos if clearances are carefully checked and maintained, and Ill be the first guy to suggest that on a stock set of heads the lunati with its lower lift is the safer choice, but on decent aftermarket heads with no clearance issues the crower design is almost sure to produce a better power curve.
Ive used several very similar cams over the years and every last one in that duration range ran better , in a TPI equipped engine with its restrictive intake, and head flow rates if the cam was retarded a few degrees (INSTALLED SPLIT OVERLAP)vs installed advanced 4 degrees (DOT-TO-DOT)the main reason seems to be that a TPI needs all the upper rpm savaging it can get to help fill the cylinders and with the limited duration the delayed intake valve closing tends to help just a bit to extend the rpm band, higher.
as IM sure your aware
the formula for hp is tq x rpm/5252
lets say the cam change moves the tq peak 150 rpm higher (WHICH IT TENDS TO)
now lets assume the torque peaks at only the same point and power peaks at
http://www.stingray.nu/tips/tech85.htm
165 NET HP @ 5200 the stock engine was supposed to make at 200rpm, higher, but it now jumps just a bit to 5350rpm,thats about 5-6 hp advantage, but in reality youll see closer to 40-60 more hp more due too both the more aggressive cam timing and the slightly retarded timing also, install it advanced and youll still get a big boost but your leaving 3-6 hp on the table in most cases
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