Camshaft/valve timing
Camshaft/valve timing
Hi. I have a 2000 coupe, lovely car, but not sure if valve timing is right. It is rough at tickover and low speeds. How can I check the timing without removing the front timing cover?
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Bert Ewalds
- Posts: 247
- Joined: 22 Dec 2008, 00:13
Re: Camshaft/valve timing
You will need a degree wheel mounted to the crankshaft pulley, and a suitable pointer, see first picture.
Next you will need a suitable dial gauge and a proper stable stand for it, second picture.
Adjust valve play for the inlet valves of Cil 1 (left bank) and 2 (right hand bank) to 0.45 mm
Turn the engine to Top Dead Centre (TDC) for Cilinder 1 on valve overlap, i.e. mark on the flywheel opposite the 1/2 mark on the flywheelhousing and both rocker arms moving when you turn the crankshaft (so not TDC for ignition)
Turn the degree wheel so that its 0 point is at your self made pointer
At 0.45mm valve play the inlet valve should open at 17degr 30' before TDC and close at 60 degr 30' beyond BDC (bottom dead Center)
Thus the valve moves over a total trajectory of 17,30' +180 (TDC to BDC)+60,30' = 258 degrees.
Maximum opening is at midpoint of this trajectory so after 129 degrees.
But since the valve starts moving 17,30'before TDC, the max opening will take place at 111degr 30'after TDC
(Data from Lancia Technical Datasheet DT Duem. 01/400 published 1971)
The dial gauge can only measure a limited stroke 3 or 4 mm typically.way less than the total rocker arm movement
So turn the engine some 100 degrees forward from TDC and mount the dial gauge in a way that it can extend about 3 quarters of its stroke.
If mounted as in the picture measurement will increase if valve is still moving dorwnwards.
Move the engine a few degrees and then adjust the gauge to a zero position on the scale.
Note down the exact degrees on the degree wheel.
Turn the engine further, the values on the gauge will increase till the point of max opening, and then start to decrease again, rotate further until it is back at the zero mark again.
Again note down the position of the degree wheel.
Subtract the starting position from this value and you you have the total number of degrees from zero to zero on the gauge.
Divide this nuber by 2 and you have the midpoint value (max opening)
Add this value to the degrees at starting point and you have the max opening point from TDC, this should be 111 degr 30' or in decimal 111.5 degrees
Plus or minus 2 degrees probably won't hurt but if its more the valve timing is out.
You have to repat the whole procedure for cilinder 2, the other bank.
By measuring from Zero to zero on the gauge, you are much more accurate than trying to read it off directly from the gauge.
Next you will need a suitable dial gauge and a proper stable stand for it, second picture.
Adjust valve play for the inlet valves of Cil 1 (left bank) and 2 (right hand bank) to 0.45 mm
Turn the engine to Top Dead Centre (TDC) for Cilinder 1 on valve overlap, i.e. mark on the flywheel opposite the 1/2 mark on the flywheelhousing and both rocker arms moving when you turn the crankshaft (so not TDC for ignition)
Turn the degree wheel so that its 0 point is at your self made pointer
At 0.45mm valve play the inlet valve should open at 17degr 30' before TDC and close at 60 degr 30' beyond BDC (bottom dead Center)
Thus the valve moves over a total trajectory of 17,30' +180 (TDC to BDC)+60,30' = 258 degrees.
Maximum opening is at midpoint of this trajectory so after 129 degrees.
But since the valve starts moving 17,30'before TDC, the max opening will take place at 111degr 30'after TDC
(Data from Lancia Technical Datasheet DT Duem. 01/400 published 1971)
The dial gauge can only measure a limited stroke 3 or 4 mm typically.way less than the total rocker arm movement
So turn the engine some 100 degrees forward from TDC and mount the dial gauge in a way that it can extend about 3 quarters of its stroke.
If mounted as in the picture measurement will increase if valve is still moving dorwnwards.
Move the engine a few degrees and then adjust the gauge to a zero position on the scale.
Note down the exact degrees on the degree wheel.
Turn the engine further, the values on the gauge will increase till the point of max opening, and then start to decrease again, rotate further until it is back at the zero mark again.
Again note down the position of the degree wheel.
Subtract the starting position from this value and you you have the total number of degrees from zero to zero on the gauge.
Divide this nuber by 2 and you have the midpoint value (max opening)
Add this value to the degrees at starting point and you have the max opening point from TDC, this should be 111 degr 30' or in decimal 111.5 degrees
Plus or minus 2 degrees probably won't hurt but if its more the valve timing is out.
You have to repat the whole procedure for cilinder 2, the other bank.
By measuring from Zero to zero on the gauge, you are much more accurate than trying to read it off directly from the gauge.
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