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PostPosted: 23 Aug 2016 14:14 
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magn1t wrote:
You've got me a bit confused here, so I'll just quote the top bit.

If all the base circles are 30 mm, that's the cam diameter at it's narrowest point.
If it's 33.40 at the widest, that's 3.40 mm cam lift.
The 5.44 mm is then valve lift?

Correct. 5.44 is the valve lift with a 3.4mm cam lift.

magn1t wrote:
Duration at 0.1 mm (close to working lash), I'd expect to be at least 250 deg?

These are the measurements I got. Going below 0.1mm was very inconsistent. There was a few times I recorded 250+ degrees on the small cams and 320+ degrees on the big cam so I disregarded these measurements due to inconsistency.

magn1t wrote:
Did you get any numbers for intake opens, intake closes, exhaust opens, exhaust closes?
Then you've got overlap too?

If set to the factory lobe centers it's easy to work out the opening and closing points (and overlap) which is why I only included duration as I didn't want to make it too cluttered with values.
But I can provide these when I'm on my laptop next if you want?
Factory lobe centers are:
Inlet small - 97 deg
Inlet big - 102.5 deg
Exhaust small - 105 deg
Exhaust big - 107.5 deg

magn1t wrote:
So same goes here, 6.40 mm of cam lift, 9.53 mm of valve lift and 278 deg of duration, which I would have expected to be a bit longer, but maybe not?
Maybe that's where the RS cams come in?

Good work, it's good to see some real measured numbers.

I'm guessing that the Mitsubishi specs of 300deg inlet and 285 deg exhaust are at lower valve lifts then I was able to accurately measure. A few times I had both inlet and exhaust at over 300deg but it just wasn't repeatable.
I also decided to focus on 0.10mm and 1.00mm as they are the common measurements for aftermarket cams (and 0.50" in US measurements) to compare with.

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PostPosted: 23 Aug 2016 14:23 
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magn1t wrote:
Cutting from your top post.
Book numbers.

Inlet low speed: 7.58mm
Inlet high speed: 10.41mm
Exhaust low speed: 8.24mm
Exhaust high speed: 9.38mm

Then your measurements.
Inlet small Lift 5.44mm
Inlet big Lift 9.53mm
Exhaust small Lift 6.73mm
Exhaust big Lift 8.76mm

It doesn't quite fit with the spec, but it's to be expected.
Maybe there's been a few revisions over the years?
If you never measured, you'd be relying on nothing other than guesswork, like everyone else does.


Yeah its a little dissapointing that the lift isnt as high as origionally thought. Most aftermarket cams are 11+mm. So even of the duration is the same there is still decent power to be made with the more lift.
Although I can understand the longer duration and small lift of the factory cams as its easy way to increase power with minimal valve train stress for the production motor that is meant to last many 100,000kms

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GT3076, Motec, Forged etc.
ADR 37/01 Legal.


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PostPosted: 25 Aug 2016 21:35 
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Talking to a mate he suggested the cams specifications that are listed on the net might be for the Gen 2 head. Maybe the measurements I got are correct for the Gen 1 Head.

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PostPosted: 26 Aug 2016 11:53 
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That's a good point.
Can you get hold of one and do some measuring?


Just think.......this forum has been around since 199X


You are the first person to measure the 4G92 cams with any sort of effort involved.




So typical internet styles..........guess, guess, guess and guess.


Love it.

Kids still can't figure out why all the modified cars blow their engines up.

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PostPosted: 28 Aug 2016 19:47 
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I unfortunately don't have access to a gen 2 head for measurement / comparison.
Looking at the cam specs I want it would be great if I could just grind 1.00mm of the base of these cams. Have the same duration just with 11 ish mm of lift but from my understanding it will through of the rocker geometry and will wear out valve guides quicker. :(

I guess I'll just have to run more boost to compensate for the lack of lift.

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GT3076, Motec, Forged etc.
ADR 37/01 Legal.


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