SPD_FRK

Cam Specifications

20 posts in this topic

Most of us V6 owners are building up our engines for increased performance with either simple bolt-ons such as air intake systems, headers, or intake manifold swaps. Some of you may be doing things internally for higher compression, or maybe just doing an engine swap.

Below is the current data we have on the 6g72, 6g74, and 6g75 Non-MIVEC OEM Camshafts. We currently do not have the valve lift specifications, but we are working to obtain this information to share within this thread. We have excluded the 6g75 MIVEC camshafts as most owners here are running the 6g72, 74, 0r 75 Non-MIVEC engines which can benefit from this information.

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 6g72,74, & 75 (Except SUV models), engines have the same intake valve duration, whereas 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 idel 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.

This is a good image that shows Lobe Seperation Angle and Valve Overlap;

LSA_021.jpg

If you have a 6g72, or 6g74 engine with OEM camshafts, then an inexpensive upgrade can be done by swapping in the Eclipse GTS 6g72, or 6g75 Non-Mivec camshafts. The 6g75 Non-MIVEC camshafts have less overlap, due to the increased Lobe Seperation Angle, this is what will yield more top end power potential than the 6g72 or 6g74 camshafts.

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and this folks, is what staying up until 4am with a good friend on the same level will get you. lol good times matt. i cant wait to get those cams sent off so we can see the fruits of our labor

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I search all over for the rocker arm ratios with no luck. All I find is the base circle for the lobes are ~35mm.

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interesting, I thought that the 6g74 had cams that were most optimized for bottom end torque and the 6g72 (none GTS) cams were better on the upper RPM range, also I thought that the 6g75 had completely diffrent cams (lots of lift and duration) than the prevous applications and now it turns out they are the same cams (on the duration front) as the GTS cams, you learn something new every day

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interesting, I thought that the 6g74 had cams that were most optimized for bottom end torque and the 6g72 (none GTS) cams were better on the upper RPM range, also I thought that the 6g75 had completely diffrent cams (lots of lift and duration) than the prevous applications and now it turns out they are the same cams (on the duration front) as the GTS cams, you learn something new every day

Keep this in mind though when you are talking about camshaft duration. Just because the duration may be the same, valve open/close timing can be different, but still result in identical duration times. The other thing to remember is just because duration is identical, it doesn't always mean the valve lift is the same either. You can have two camshafts with a 248/256 duration, but one may have more lift than the other.

Until we can get our OEM 75 Non-MIVEC cams spec'd out for lift, nobody can say without hard documentation for a fact that the Eclipse GTS & 75 Non-MIVEC cams are identical.

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This just dawn on me: Someone with a 72/74 head and 75 head, take the measurements of the valves at the peak or nose of the cam lobe from the valve seat to where the valve protrune the most. To determine the ratio of the rocker arms, valve lift divided by the subtraction the cam height by the lobe base circle (Valve Lift / [Cam Height - Lobe Base Circle]).

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Well I finally made some additional progress here with this stuff, mainly because we are gearing up for the start of our own camshafts that we hope to start getting some R&D on over the next few months.

I measured out the 6g72 & 6g75 Non-MIVEC cams today using a Mitutoyo calipers on the intake and exhaust lobes. I first measured for the lobe circle, and then measured the lobe height. Now the measurements I got were as followed;

6g72

Intake Lobe Circle: 1.263"

Intake Lobe Height: 1.485"

Exhaust Lobe Circle: 1.263"

Exhaust Lobe Height: 1.470"

6g75 Non-MIVEC

Intake Lobe Circle: 1.263"

Intake Lobe Height: 1.485"

Exhaust Lobe Circle: 1.263"

Exhaust Lobe Height: 1.470"

Now, these were my own measurements, which I am going to re-check again tomorrow, specifically for the Lobe Circle measurements as RPW states "standard Mitsu base circle of 1.180" being used for their camshafts. With that information taken into consideration below is what I have found for the valve lift on the stock camshafts;

6g72

Intake Lift: .305" (Per RPW base circle specs)

Intake Lift: .222" (Per my own current measurements)

Exhaust Lift: .290" (Per RPW base circle specs)

Exhaust Lift: .207" (Per my own current measurements)

6g75 Non-MIVEC

Intake Lift: .305" (Per RPW base circle specs)

Intake Lift: .222" (Per my own current measurements)

Exhaust Lift: .290" (Per RPW base circle specs)

Exhaust Lift: .207" (Per my own current measurements)

Now based on the above information, we now know for certain that the camshafts between the 6g72, 6g74, & 6g75 have only one key difference. The 6g75 has a 248* Intake duration, whereas the Exhaust duration is 256*. The valve lift between the 3 models were never changed apparently, the only change made with the duration makes sense as a longer duration on the exhaust lobes will reduce EGTs (Exhaust Gas Temperatures), and this ultimately helps to improve fuel economy.

Again, I will be going back to my lobe circle measurements again tomorrow, and double checking everything quite closely to ensure I can obtain as accurate information as possible, but for now we are making some great progress for our community's documentation, as well as our own information for our own camshafts.

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Alright, as of right now the measurements I have taken for the base circle of the lobes are correct. I had all lobes checked between the two cams, myself as well as two engineers at work checked these again. Measurements varied no more than 1.262-1.264", in order to try and find RPW's "standard Mitsu 1.181" base circle" measurement. I even went down to measuring the bare casting area between each cam lobe and saw measurement of 1.002" at most. to try and replicate RPW's spec reference they seem to use on their cams.

I will go one step further and note some additional, and easily found resources direct from the 8th Gen FSM (Page 11D-58, under Service Specifications). Camshaft cam height (basically lobe height) is as follows;

Intake Standard Value - 1.485"

Intake Limit Value - Minimum 1.465"

Exhaust Standard Value - 1.462"

Exhaust Limit Value - Minimum 1.443"

9th Gen FSM for 6g75, 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"

As for condition of the cams, I am comparing stock 6g72 cams with 172K miles on them, and the 6g75 cams had 143K on them...so any wear on material should have been easily noted. *If you caught it already, yes I may have flipped my intake and exhaust lobe height measurements on the paper I wrote them down on, just caught it now myself so will recheck that all as well and get t cleared up to eliminate any confusion of the information here.

I also found the rocker ratio for the 6g7x series engines is apparently a 1.6, so given what I have found for cam lobe height based on my measurements this is what the actual valve lift should be I guess;

Valve Lift = Lobe Height X Rocker Ratio

My 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 trying to find how RPW obtained the "standard Mitsu 1.181" base circle" specs given what I have found on two highly used OEM cams of my own, and the cam specs I am getting as a result with them. For finding our OEM valve lift specs I believe it is highly creditable and reasonable to go off of my measurements given what I have found, and no further documentation in the 8th-9th Gen FSMs on the measurement.

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).

Hopefully some of you are reading this stuff and learning, or at least able to follow along with my rambling lol....just trying to put in a lot of leg work on our end before we start with our camshafts.

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well now. this is much different than we first expected. and by a lot. i mean even if the stage 3 rpws do have .549 lift, thats a TON of lift. not even vr4 280's have that much lift. no evo cam even has a lift like that and for a cam designed for a piston that really has no valve reliefs in it, boy thats going to be cutting it close

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Idk if it is a ton of lift. While searching for rocker ratio information I ran across some 6g72 DOHC stuff which stated OEM lift for them was just over .350", with rocker ratio of 1.72 or 1.76 IIRC. With stock cams that puts their lift to .602"-.616" depending on the rocker specific rocker ratio.

You are right though, valve to piston clearance will undoubtedly become an issue for high lift cams, more so on my own build due to the heavily milled heads and already running a .070"-.095" valve to piston clearance.

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The 6G7x DOHC has the same rocker arm ratio as the 4G6x DOHC, same cam base circle as well. It seems like RPW mistakely have the 4G6x DOHC base cam circle listed for the 6G7x SOHC as ~30mm = 1.180"

Also, seems like the 4G64 and 6G7x SOHC share a similar valvetrain components: rocker arms, valves, valve springs, etc.

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Updated original posting to correct GTS cam specs, and added specifics for 6g75 and 6g74 cma profiles that vary depending on model year and vehicle model.

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One of the major setbacks we have for making our own cams is that most manufactureres, like cosworth, make a few different grinds that they've calculated to be optimal in power range they desire and then dyno test them to see what works best. We can certainly calculate something close, but we won't know what will for sure make the most power until we can run different profiles side by side to see what works better.

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Bringing this discussion back to life.....

 

I have just installed the adjustable cam gears on my 6G75 (6G74 block) 

 

I found some interesting results, these cams are the stock 6G75 camshaft supplied in the 2007 AU Mitsubishi 380 sedan, like a Magna....

 

After participating in a discussion on the AU Magna forum, I learned that advancing the camshaft timing about 6 degrees should bring on more torque at lower rpm and be a good starting point for tuning/testing.

 

So the results are as follows;

 

Intake lobe lift at camshaft is 6.3mm or 0.248 inch

 

Exhaust lobe lift at camshaft is 5.6mm or 0.220 inch

 

 

initially I set the adjustable gears to zero or stock and took some measurements with the dial indicator.

 

The Drivers side or no. 1 piston Inlet valve started moving at 6 degrees BTDC (crankshaft)

The Passenger side or no. 2 piston inlet valve started moving at 0 degrees or TDC

 

So I advanced both camshaft gears to have the Inlet valve starting to open at 15 degrees BTDC (crankshaft)

 

These measurements are all taken with the dial indicator sitting on top of the rocker arm directly above the valve

 

Intake opens 15 Deg BTDC

Intake closes 80 Deg ABDC

 

Intake centreline is 115 Deg

 

Exhaust opens 55 Deg BBDC

Exhaust closes 50 Deg ATDC

 

Exhaust centreline is 100 Deg

 

What is interesting is the duration of both intake and exhaust is a lot longer than any specs I have seen.

 

I double checked both banks and got slight variations but only by a couple of degrees.

 

Not really sure why, any thoughts ?

Edited by salt36

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what about valve clearance? Have there been any issues? I have the 6g72 and would like a little tougher cam. Now would be a good time as I'm getting ready to redo the engine after a timing belt snap.

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Ralliart Magna (duration same as 2002+ Diamante; Mitsubishi 380 have the same specs.)

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

Intake Valve Lift: 10mm

Exhaust Valve Lift: 9.5mm

 

tien99gtz likes this

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