Camshaft deegreeing question

[delcbr]

valve clearances are 0.25mm
If I am setting the cam up with the opening and closing points And the Timing card states Timing of inlet @1mm opens -7 and closes 57 degrees
So the question is do I still take it to 1mm or do I subtract or add the 0.25mm?

[PaulKemp]

Valve clearance is the gap between cam love and bucket or vale tip
The 1mm measurement I guess is inlet valve lift on No.1 cylinder at TDC, measured with dial gauge

[stevesingo]

What you could do is work out peak lift which is peak lift regardless of clearance, and set the cam to that.

Open 7 Before TDC
+ 180
Close 57 After BDC

Full duration= 7+180+57= 244

Mid point of cam duration 244/2=122

Peak lift - open AFTER TDC - peak lift= 122-7=115

It is difficult to set using peak lift as the cam dwells on peak lift for several degrees. To get around this bracket peak lift point at say peak lift -0.5mm.

Turn the engine until you reach peak lift and zero the Dial Indicator. Turn through another cycle to peak lift -0.5mm on the opening side and note the crank angle eg 105deg.

Continue turning until you pass peak lift and get to peak lift -0.5mm on the closing side eg 125deg

125-105=20

20/2=10

105+10=115. If it is not correct then adjust the cam to suit and repeat.

It is best if you set the cam up advanced to start with and end up with a peak lift of eg 105, you can turn the engine to 105(peak lift), slacken the vernier and turn the engine (whilst looking at the dial indicator to ensure the cam hasn't moved) until the crank reaches 115deg. Tighten the vernier and recheck.

Edited by stevesingo on Friday 26th September 07:19

[delcbr]

Stevesingo very useful information there thanks. It does state that the lobe angle is 122 degrees so is that not where I set peak lift midpoint?

[DVandrews]

Ask them for the lift at TDC, this is far easier to check and set and in the main it can be achieved with greater accuracy.

Dave

[226bhp]

DVandrews said:

Ask them for the lift at TDC, this is far easier to check and set and in the main it can be achieved with greater accuracy.

Dave

Doesn't that depend whether they have quoted it with clearance or not? He will still have the same problem.

[226bhp]

delcbr said:

valve clearances are 0.25mm
If I am setting the cam up with the opening and closing points And the Timing card states Timing of inlet @1mm opens -7 and closes 57 degrees
So the question is do I still take it to 1mm or do I subtract or add the 0.25mm?

Ask the cam manufacturer, it's the only way. Some quote with lash, others not, it should be outlined on the timing card.

[stevieturbo]

delcbr said:

valve clearances are 0.25mm
If I am setting the cam up with the opening and closing points And the Timing card states Timing of inlet @1mm opens -7 and closes 57 degrees
So the question is do I still take it to 1mm or do I subtract or add the 0.25mm?

1mm lift at the valve is 1mm lift. That is not a variable. Likewise they have given you a specific cam/follower clearance to work with. Again this is not a variable

There should be no adding or subtracting anything as you would be measuring valve/follower lift.

[DVandrews]

As above, lift is always lift that you measure at the valve or follower, this means as measured it is nett of any clearance and is quoted as such.

Dave

[delcbr]

Ok thanks for all the help from everyone to let you all understand it's a set of used PTG cams 280 degree for a BMW. PTG were a BMW racing company in the USA.I have no other information to help me degree them. The figures I quoted were for a set of similar cams for my engine from catcams.
The cams I have already fitted to my engine using BMW can setting tools as the camshafts are BMW parts the engine revs smoothly and quickly but I feel it's lacking power in the high rpm area maybe not enough overlap for scavenging to take place.
So now I want to explore at what degrees when are the valves opens and closing and compare to Schrick and catcam offerings. So that's why it was important for me to know if I needed to factor in the valve clearances.

[delcbr]

The exhaust lobe angle is 108 degrees.
So at 108 degrees on the timing disc it should be at maximum lift midpoint?
Using catcams values it says opens 43 degrees closes 7 degrees,
43+180+7=230
230/2=115
115-7=108
Is that how you set it up for exhaust?

But the one for inlet lobe centre is 122 which I thought is where I set max lift mid point but you said 115 degrees?

[stevieturbo]

If the engine is already built and running with cams of unknown specs, stop wasting your time guessing numbers.

Take it to a dyno and have them swing the cam to see which gives you the best results.

[delcbr]

Can't do that unfortunately. There is no adjustment possible as it's chain and fixed sprockets. I would have to remove the vanos to move the camshaft to another position then refit vanos again.

[stevesingo]

delcbr said:

The exhaust lobe angle is 108 degrees.
So at 108 degrees on the timing disc it should be at maximum lift midpoint?
Using catcams values it says opens 43 degreesBBDC closes 7 degreesATDC,
43+180+7=230
230/2=115
115-7=108
Is that how you set it up for exhaust?

That sounds fine.


But the one for inlet lobe centre is 122 which I thought is where I set max lift mid point but you said 115 degrees?

Where does it state 112 intake lobe centre?

[delcbr]

Stevesingo this is the standard information here
http://www.catcams.com/products/camshafts/datashee...

[stevesingo]

The way I read that is that you disengage the VANOS and set the cam in the fully retarded position. i.e 122.

[carlt5]

Simple question sort of relating to this topic ,as I want to measure actual valve timing figures for some unknown cams I have.
As a generalisation , when a tappet/follower clearance is set ,e.g. 10thou" cold , how much of that clearance reduces when an engine is at running temp.- e.g. does it close to 2thou"clearance ?
i.e. if I want to measure actual valve opening point , relative to crank rotation, on a cold engine what should the tappet clearance be set at

cheers
carl

[delcbr]

That's what I was trying to ask too :-)
Couldn't find a definite answer from googling and researching but found no mention of deducting valve clearance from measuring the valve opening and closing in degrees. Only deducting the valve clearance when measuring valve lift at TDC.
There's a part of the camshaft called the heel which then leads onto the ramp which is the part which gently brings the camshaft into contact with the cam follower then once in contact it moves onto the Flank.
The other thing worth mentioning is measuring duration at 1mm lift actual duration as it tells you more about the duration than measuring at 0.1mm which is advertised duration.
http://www.tildentechnologies.com/Cams/CamBasics.h...

[carlt5]

ok- found this from Crane Cams
http://www.cranecams.com/pdf-tech-tips/mech-lift.p...

[delcbr]

I read the crane cams article. It doesn't apply to measuring cam duration it's only for setting the valve clearances.
Read this instead
http://www.catcams.co.uk/acatalog/Durations_Explai...