Unknown Cam Shaft - Measure & Plot Lift to Determing Overlap/Timing?
 

I'm interested in knowing if its reasonably possible to figure out what camshaft (or grind) i/you/anyone has, with out looking at the part numbers. I have looked at a few you tube videos, and have an idea of the basic lobe measurements, Im specifically intereste to know if it is it possible to plot one of these graphs below, and use the overlap point as the timing, or is this a really really bad idea, and i need to go to my local engine shop now, and hand it over.

If such a graph can be reliably used. Do you set the intake and exhaust valve adjustment (free play) at 0.1mm or with no (0mm). I have one side of the engine stripped and the other side complete with cam shaft, chain, hydraulic tensioner, etc.

(Wayne, aplogies for using your graph - i do own 3 copies of your rebuild book (seriously), 2 copies of your 101 book, and 101 for 996, plus im a good customer, lol)

p.s I have already marked the crank pully at 5 deg intervals from 40 BTDC to ATDC, and have graphed the intake (i'll do the exhaust 2moro). I short cutted the graph to just the area around the overlap - i'll post my graph 2moro even if its not right! I have both valves set at 0.1mm (0.004")

Here is how I did this

http://forums.pelicanparts.com/911-engine-rebuilding-forum/530913-diy-cam-doctor.html

hi tom, that is exactly what i was thinking.

I have been using the crank shaft for degrees, but from reading i need to bolt the pulley on to the cam and do it that way.

Did you do it with 0.004" valve clearance or with 0 clearance?

Camshaft specs are measured based on crankshaft rotation degrees, so put the degree wheel there. You can put the valve lash to 0" (no lash) for degreeing your camshaft. You can plot a graph if you take patient measurements, but note that if you're looking to just identify a cam grind, the key measurements that are *reasonably* unique are duration, max lift, and lobe centers. All can be measured pretty easily with a degree wheel and a dial indicator with a mount to measure valve lift. Note that for duration, some measure at 1 mm, some measure from zero lift, and some measure at .050" lift, so make sure you're comparing apples to apples. Duration values can vary significantly depending on which value you are using for your measurements.

Scott

Thanks stowen, i'll do some research on it, im a bit hazy on the terms, but i'll research it and figure it out. I know im playing mega safe, i could just hand my cam over to someone, but i like learning, it helps me understand it all!