CAMSHAFT SPECIFICATIONS

Hey guys,

i did the timing degree course but i have a question about the cam specifications, what means the 'intake: @.040"' above the text ->

intake: @.040"

opening: 30° BTDC

peak lift: 100° ATDC

closing: 50°ABDC

camms: skunk2 pro2

engine: F20C

car: Honda s2000

Because different camshaft manufacturers have used different lift points for specifying their duration which make is rather difficult to compare grinds, and because the initial ramp/opening is usually less significant, a standard lift point has become a de-facto standard.

Most American domestic camshafts are 0.050" lift, the European/Japanese (metric?) standard may be 1mm/0.040", but I can't say for sure.

It should also be a bit more accurate when degreeing.

Thankyou for the answer.

so if i understand right i have to reach .040 lift at 30degree BTDC? And understanding ‘lift’ is when valve start to open(pushing open) or start to close again?(from IVO .040?)

When you set intake camshaft up ready for degreeing ( providing you already made the degreeing wheel to represent true TDC)you also install a dial indicator to measure the lift of the valve in fully closed position. You start rotating crankshaft ( counterclockwise since it's Honda) and watch the dial indicator - at the mark of 30 degrees before TDC it should show you that the valve moved up 1mm (0.040 inch). If that's the case then your camshaft setting is right on the money and if you'll keep rotating the crankshaft you will find that the valve maximum lift will take place at 100 degrees after TDC. After that the valve will start slowly closing and you will find that it will move to 1mm lift at 50 degrees after BDC before completely going back to fully closed position.

If your opening and closing points are not matching these requirements you need to change position of the camshaft in relation to crankshaft -you'll need to rotate it inside of the cam sprocket where rotating direction will depend on the actual opening/closing points found during degreeing process- it might be advancing the camshaft or retarding it.

The same technique should be used for exhaust camshaft.

Thankyou for this wonderful explanation! I did it now and i understand 200%!

As Shota said.

There is one caveat, though - some may use camshaft lift, at the lobe from the base circle, others will use valve lift when set to the correct clearance. This looks like the latter and you can verify it as Shota said - eg. for the inlet check the 30 BTDC and 50 ABDC points corrolate and if they're, say, 40 and 60 or 20 and 40, respectively, you have the wrong checking clearance.

Modern engines are done this way because the valve train geometry means the old method of splitting the difference for maximum lift doesn't work