SPD_FRK
12-28-2012, 04:56 PM
Below is the current and accurate data on the 6g72, 6g74, and 6g75 Non-MIVEC OEM Camshafts.
6g72 Camshafts
(Galant & Eclipse GT Model)
Intake Opens (BTDC) 15*
Intake Closes (ABDC) 53*
Exhaust Opens (BBDC) 53*
Exhaust Closes (ATDC) 15*
248* Intake Valve Duration
248* Exhaust Valve Duration
109* Lobe Seperation Angle
30* Valve Overlap
(Eclipse GTS Model)
Intake Opens (BTDC) 7*
Intake Closes (ABDC) 61*
Exhaust Opens (BBDC) 57*
Exhaust Closes (ATDC) 15*
248* Intake Valve Duration
252* Exhaust Valve Duration
115* Lobe Seperation Angle
22* Valve Overlap
6g74 Camshafts
(1997-2001 Model Years)
Intake Opens (BTDC) 9*
Intake Closes (ABDC) 59*
Exhaust Opens (BBDC) 47*
Exhaust Closes (ATDC) 21*
248* Intake Valve Duration
248* Exhaust Valve Duration
109* Lobe Seperation Angle
30* Valve Overlap
(2002+ Model Years)
Intake Opens (BTDC) 13*
Intake Closes (ABDC) 55*
Exhaust Opens (BBDC) 51*
Exhaust Closes (ATDC) 17*
248* Intake Valve Duration
248* Exhaust Valve Duration
109* Lobe Seperation Angle
30* Valve Overlap
6g75 Non-MIVEC Camshafts
(Galant Models)
Intake Opens (BTDC) 7*
Intake Closes (ABDC) 61*
Exhaust Opens (BBDC) 61*
Exhaust Closes (ATDC) 15*
248* Intake Valve Duration
256* Exhaust Valve Duration
115* Lobe Seperation Angle
22* Valve Overlap
(Endeavor & Montero Models)
Intake Opens (BTDC) 5*
Intake Closes (ABDC) 55*
Exhaust Opens (BBDC) 51*
Exhaust Closes (ATDC) 17*
240* Intake Valve Duration
248* Exhaust Valve Duration
111* Lobe Seperation Angle
22* Valve Overlap
As you can see the engines have the same intake valve duration, whereas the 6g72 in the Eclipse GTSm, and the 6g75 Non-MIVEC engines have a longer exhaust valve duration as well as less valve overlap. What is valve overlap? Overlap is where both the intake and exhaust valves are open at the same time on each cylinder (this occurs around Top Dead Center or TDC). Excessive valve overlap is something commonly found on racing engines, too much overlap also results in rough idle conditions. A lot of overlap favors higher RPM range performance ranther than lower RPM range. A certain amount of valve overlap is beneficial, without it volumetric efficiency of the engine is usually compromised.
Lobe seperation angle: a wider lobe-separation angle (overlap decreases) improves idle quality, idle vacuum and helps top-end power (say 112 to 116 degrees for example). A tighter lobe-separation angle (104 to 110 degrees) will produce a rough idle and better midrange torque but limit top-end power.
Valve Lift Specifications & Tech Information
I measured two sets of 6g72 cams, and a set of 6g75 Non-MIVEC cams using a Mitutoyo calipers. These were my own measurements, and to be as accurate as possible I had all lobes checked for each set of cams. I enlisted the assistance of two engineers who are high end machinists for 20+ years for a company called Sundyne. All of our measurements had no more than a +/- .002” variance.
Here is where we ran into conflicting information between our own measurements and those stated by RPW's measurements. RPW states a "standard Mitsubishi base circle of 1.180" being used for their camshafts. We even went as far as measuring the bare casting area between each cam lobe where the best measurement we obtained was 1.002" maximum between 3 different sets of the 6g7x series camshafts.
I will go one step further and note additional creditable documentation that is easily found in the Factory Service Manual. Here I reference from the 8th Gen Galant FSM (Page 11D-58, under Service Specifications). Camshaft cam height (basically lobe height) is as follows;
8th Gen Galant – Page 11D-58
Intake Standard Value - 1.485"
Intake Limit Value - Minimum 1.465"
Exhaust Standard Value - 1.462"
Exhaust Limit Value - Minimum 1.443"
9th Gen Galant FSM - Page 11D-63
Intake Standard Value - 1.472"
Intake Limit Value - Minimum 1.452"
Exhaust Standard Value - 1.485"
Exhaust Limit Value - Minimum 1.465"
With that information taken into consideration below is what I have found for the valve lift on the stock camshafts. I first measured for the lobe circle, and then measured the lobe height. Now the measurements were as followed;
6g72 Galant & Eclipse GT
Intake Lobe Circle: 1.263"
Intake Lobe Height: 1.485"
Intake Lift: .305" (Per RPW base circle specs)
Intake Lift: .222" (Per my own current measurements)
Exhaust Lobe Circle: 1.263"
Exhaust Lobe Height: 1.470"
Exhaust Lift: .290" (Per RPW base circle specs)
Exhaust Lift: .207" (Per my own current measurements)
6g75 Non-MIVEC Galant
Intake Lobe Circle: 1.263"
Intake Lobe Height: 1.485"
Intake Lift: .305" (Per RPW base circle specs)
Intake Lift: .222" (Per my own current measurements)
Exhaust Lobe Circle: 1.263"
Exhaust Lobe Height: 1.470"
Exhaust Lift: .290" (Per RPW base circle specs)
Exhaust Lift: .207" (Per my own current measurements)
Actual Valve Lift -
I found the rocker ratio for the 6g7x series engines is apparently 1.6, so given what we have found for cam lobe height this is what the actual valve lift should be I guess;
Valve Lift = Lobe Height X Rocker Ratio
Our measurements;
Intake Lobe Height .222"
Exhaust Lobe Height .207"
.222" x 1.6 =.355" Lift (9.017mm)
.207" x 1.6 = .331" Lift (8.407mm)
RPW Spec (1.181" lobe base circle)
Intake Lobe Height .305"
Exhaust Lobe Height .290"
.305" x 1.6 =.488" Lift (12.395mm)
.290" x 1.6 = .464" Lift (11.786mm)
So what does all of this mean? Well that is the difficult part and I am still struggling with trying to find where/how RPW obtained the "standard Mitsubishi 1.181" base circle" specs given what we have found on 3 sets of highly used OEM camshafts. This base circle measurement, as well as the cam specifications we are getting as a result from different measurements.
The question that begs to be asked is if the RPW valve lift specs are actual valve lift, or lobe height? Let's take their Stage 3 cams with .343" advertised lift for example. As we know the Rocker Ratio plays a part in finding the actual valve lift so we will factor this in here as well.
.343" x 1.6 = .549" Valve Lift
If the .343" is actual valve lift, then let's flip the equation to find out for reasonable doubt;
.343"/1.6 = .214" Valve Lift
With that I think it is safe to say the advertised valve lift of .343" is just part of the lobe height measurement on the cam, and actual valve lift is really .549" (13.945mm) vs .214" (5.436mm).
Valve Spring Specifications/Tech
OEM 6g7X Valve Spring Demensions
Installed height is 1.74"
Seat pressure of 60lbs
Spring ID - .639" (+/- .01")
Spring OD - .981" (+/- .01")
6g72 Camshafts
(Galant & Eclipse GT Model)
Intake Opens (BTDC) 15*
Intake Closes (ABDC) 53*
Exhaust Opens (BBDC) 53*
Exhaust Closes (ATDC) 15*
248* Intake Valve Duration
248* Exhaust Valve Duration
109* Lobe Seperation Angle
30* Valve Overlap
(Eclipse GTS Model)
Intake Opens (BTDC) 7*
Intake Closes (ABDC) 61*
Exhaust Opens (BBDC) 57*
Exhaust Closes (ATDC) 15*
248* Intake Valve Duration
252* Exhaust Valve Duration
115* Lobe Seperation Angle
22* Valve Overlap
6g74 Camshafts
(1997-2001 Model Years)
Intake Opens (BTDC) 9*
Intake Closes (ABDC) 59*
Exhaust Opens (BBDC) 47*
Exhaust Closes (ATDC) 21*
248* Intake Valve Duration
248* Exhaust Valve Duration
109* Lobe Seperation Angle
30* Valve Overlap
(2002+ Model Years)
Intake Opens (BTDC) 13*
Intake Closes (ABDC) 55*
Exhaust Opens (BBDC) 51*
Exhaust Closes (ATDC) 17*
248* Intake Valve Duration
248* Exhaust Valve Duration
109* Lobe Seperation Angle
30* Valve Overlap
6g75 Non-MIVEC Camshafts
(Galant Models)
Intake Opens (BTDC) 7*
Intake Closes (ABDC) 61*
Exhaust Opens (BBDC) 61*
Exhaust Closes (ATDC) 15*
248* Intake Valve Duration
256* Exhaust Valve Duration
115* Lobe Seperation Angle
22* Valve Overlap
(Endeavor & Montero Models)
Intake Opens (BTDC) 5*
Intake Closes (ABDC) 55*
Exhaust Opens (BBDC) 51*
Exhaust Closes (ATDC) 17*
240* Intake Valve Duration
248* Exhaust Valve Duration
111* Lobe Seperation Angle
22* Valve Overlap
As you can see the engines have the same intake valve duration, whereas the 6g72 in the Eclipse GTSm, and the 6g75 Non-MIVEC engines have a longer exhaust valve duration as well as less valve overlap. What is valve overlap? Overlap is where both the intake and exhaust valves are open at the same time on each cylinder (this occurs around Top Dead Center or TDC). Excessive valve overlap is something commonly found on racing engines, too much overlap also results in rough idle conditions. A lot of overlap favors higher RPM range performance ranther than lower RPM range. A certain amount of valve overlap is beneficial, without it volumetric efficiency of the engine is usually compromised.
Lobe seperation angle: a wider lobe-separation angle (overlap decreases) improves idle quality, idle vacuum and helps top-end power (say 112 to 116 degrees for example). A tighter lobe-separation angle (104 to 110 degrees) will produce a rough idle and better midrange torque but limit top-end power.
Valve Lift Specifications & Tech Information
I measured two sets of 6g72 cams, and a set of 6g75 Non-MIVEC cams using a Mitutoyo calipers. These were my own measurements, and to be as accurate as possible I had all lobes checked for each set of cams. I enlisted the assistance of two engineers who are high end machinists for 20+ years for a company called Sundyne. All of our measurements had no more than a +/- .002” variance.
Here is where we ran into conflicting information between our own measurements and those stated by RPW's measurements. RPW states a "standard Mitsubishi base circle of 1.180" being used for their camshafts. We even went as far as measuring the bare casting area between each cam lobe where the best measurement we obtained was 1.002" maximum between 3 different sets of the 6g7x series camshafts.
I will go one step further and note additional creditable documentation that is easily found in the Factory Service Manual. Here I reference from the 8th Gen Galant FSM (Page 11D-58, under Service Specifications). Camshaft cam height (basically lobe height) is as follows;
8th Gen Galant – Page 11D-58
Intake Standard Value - 1.485"
Intake Limit Value - Minimum 1.465"
Exhaust Standard Value - 1.462"
Exhaust Limit Value - Minimum 1.443"
9th Gen Galant FSM - Page 11D-63
Intake Standard Value - 1.472"
Intake Limit Value - Minimum 1.452"
Exhaust Standard Value - 1.485"
Exhaust Limit Value - Minimum 1.465"
With that information taken into consideration below is what I have found for the valve lift on the stock camshafts. I first measured for the lobe circle, and then measured the lobe height. Now the measurements were as followed;
6g72 Galant & Eclipse GT
Intake Lobe Circle: 1.263"
Intake Lobe Height: 1.485"
Intake Lift: .305" (Per RPW base circle specs)
Intake Lift: .222" (Per my own current measurements)
Exhaust Lobe Circle: 1.263"
Exhaust Lobe Height: 1.470"
Exhaust Lift: .290" (Per RPW base circle specs)
Exhaust Lift: .207" (Per my own current measurements)
6g75 Non-MIVEC Galant
Intake Lobe Circle: 1.263"
Intake Lobe Height: 1.485"
Intake Lift: .305" (Per RPW base circle specs)
Intake Lift: .222" (Per my own current measurements)
Exhaust Lobe Circle: 1.263"
Exhaust Lobe Height: 1.470"
Exhaust Lift: .290" (Per RPW base circle specs)
Exhaust Lift: .207" (Per my own current measurements)
Actual Valve Lift -
I found the rocker ratio for the 6g7x series engines is apparently 1.6, so given what we have found for cam lobe height this is what the actual valve lift should be I guess;
Valve Lift = Lobe Height X Rocker Ratio
Our measurements;
Intake Lobe Height .222"
Exhaust Lobe Height .207"
.222" x 1.6 =.355" Lift (9.017mm)
.207" x 1.6 = .331" Lift (8.407mm)
RPW Spec (1.181" lobe base circle)
Intake Lobe Height .305"
Exhaust Lobe Height .290"
.305" x 1.6 =.488" Lift (12.395mm)
.290" x 1.6 = .464" Lift (11.786mm)
So what does all of this mean? Well that is the difficult part and I am still struggling with trying to find where/how RPW obtained the "standard Mitsubishi 1.181" base circle" specs given what we have found on 3 sets of highly used OEM camshafts. This base circle measurement, as well as the cam specifications we are getting as a result from different measurements.
The question that begs to be asked is if the RPW valve lift specs are actual valve lift, or lobe height? Let's take their Stage 3 cams with .343" advertised lift for example. As we know the Rocker Ratio plays a part in finding the actual valve lift so we will factor this in here as well.
.343" x 1.6 = .549" Valve Lift
If the .343" is actual valve lift, then let's flip the equation to find out for reasonable doubt;
.343"/1.6 = .214" Valve Lift
With that I think it is safe to say the advertised valve lift of .343" is just part of the lobe height measurement on the cam, and actual valve lift is really .549" (13.945mm) vs .214" (5.436mm).
Valve Spring Specifications/Tech
OEM 6g7X Valve Spring Demensions
Installed height is 1.74"
Seat pressure of 60lbs
Spring ID - .639" (+/- .01")
Spring OD - .981" (+/- .01")