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Ssaga

Cam card figures vs measured figures

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Ssaga    10
Posted (edited)

I while back I took my car, (280z) to a dyno the result, (discussed in separate thread,http://forums.hybridz.org/topic/127636-thoughts-on-my-dyno-result-280z-triple-webers/?hl=%2Bdyno+%2Bresult

 

I contined the investigation regarding the strange figures.

I surely have jetting isusue, I however also discovered that my cam was way to retarded.

After several measurements with degree wheel and indicator clock I decided to move the

cam one notch forward.

 

After this the measurements look quit ok, would probably be a even better with adjustable cam sprocket

After advancing the cam these are the figures i got.

Max lift intake lobe at 105 degres, approx 12,3 mm, defined max lift according to cam card 12,57 mm at 104 degreess

Max lift Exhaust at 111 degrees, approx 12,3 mm, defined max lift according to cam card 12,57 mm at 108 degreess

 

Intake lift at overlap 4,5mm

Exhaust lift at overlap 3,5mm

 

Below are figures I measured when camshaft mounted in engine.

 

At 0,05 inch.

Exhaust opens 65 degree BBDC

Exhaust closes 17 degree ATDC.

 

Intake opens 27 degree BTDC

Intake closes 51 degree ABDC

 

 

 

Overlap 44 degrees

Overlap according to cam card 32 degrees

 

The Duration I get with measured figures

Intake 258 degrees

Exhaust 262 degrees.

 

Figures according to the cam card.

Exhaust opens 50 degrees BBDC

Exhaust closes 14 degrees ATDC

 

Intake opens 18 degrees BTDC

Intake closes 46 degrees ABDC

 

Duration according to cam card.

Intake 244

Exhaust 244

 

 

What I don´t understand is the differences in Duration and overlap when comparing to the cam card, this is very strange to me.

 

I´m measuring this with valve play at 0,08 inch as stated in cam card and at the valve retainer.

There are certainly some degrees here and there that are incorrect, but as whole I think this is correct.

The big picture is showing a quit a big difference in Duration and overlap.

 

I´m I missing something when measuring?

The feedback I get from supplier are more aiming towards that the Max lift should be at the correct timing, and not

focus on Duration and Overlap.

For me this is a bit strange, I would like to know the actual Duration and overlap of the cam in the car.

 

Grateful for any help.

 

/Henrik

Edited by Ssaga

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TimZ    21

Below are figures I measured when camshaft mounted in engine.

 

At 0,05 inch.

Exhaust opens 65 degree BBDC

Exhaust closes 17 degree ATDC.

 

Intake opens 27 degree BTDC

Intake closes 51 degree ABDC

 

 

 

Overlap 44 degrees

Overlap according to cam card 32 degrees

 

The Duration I get with measured figures

Intake 258 degrees

Exhaust 262 degrees.

 

Figures according to the cam card.

Exhaust opens 50 degrees BBDC

Exhaust closes 14 degrees ATDC

 

Intake opens 18 degrees BTDC

Intake closes 46 degrees ABDC

 

Duration according to cam card.

Intake 244

Exhaust 244

 

 

What I don´t understand is the differences in Duration and overlap when comparing to the cam card, this is very strange to me.

 

I´m measuring this with valve play at 0,08 inch as stated in cam card and at the valve retainer.

There are certainly some degrees here and there that are incorrect, but as whole I think this is correct.

The big picture is showing a quit a big difference in Duration and overlap.

 

I´m I missing something when measuring?

The feedback I get from supplier are more aiming towards that the Max lift should be at the correct timing, and not

focus on Duration and Overlap.

For me this is a bit strange, I would like to know the actual Duration and overlap of the cam in the car.

 

Grateful for any help.

 

/Henrik

 

I _have_ seen cam cards where the 0.050" events were to be measured at the cam instead of at the valve, even though it said nothing about this and everything else was measured at the valve.  The results of this are consistent with what you are describing -perhaps try repeating your measurements using 0.075" (0.050" x 1.5 rocker ratio) lift at the valve and see if they make more sense.

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