I put together a builders prepared engine kit from ARC racing. the kit came with valve timing cards that read.
INTAKE : open- 46.3
C/L- 108.5 atdc
close- 82.7 abdc
Dur @ .050* : 245.7 deg.
lift - .2245
EXHAUST : open- 83 bbdc
close- 44 atdc
lift- .231
c/l - 110 btdc
I plan on building another one.What are these numbers? How can I learn them in laymans terms? Do I really need to know what they mean? I'm sorry if its a lot to ask but I would really like to know. Always THANKS to all that help here at DIY.
Looks like a MOD2 Cam.
I started to write an explanation, but feared it would confuse you more.
It took me a while of studying camshafts to gain an understanding.
If nobody answers soon, I write a explanation when I have more time.
Youtube camshaft specs and you'll find a number of good videos explaining the specs.
Lift describes how high the valve lifts off the valve seat.
Duration describes how long the valve stays open.
Opening describes at what point in the crankshaft rotation the valve lifts off the seat.
Closing describes at what point in the crankshaft rotation the valve returns to the seat.
C/L is center line. It describes the midpoint of the lift, where max lift occurs (on symmetrical shaped lobes).
ATDC means after top dead center
BTDC means before top dead center
ABDC means after bottom dead center
BBDC means before bottom dead center
When the piston is as high as it gets in the cylinder, that is known as top dead center.
When the piston is as low as it gets in the cylinder, that is known as bottom dead center.
It is important to understand where the piston is and in what direction it is traveling at each of the opening and closing events. So the first things to get a complete understanding of are the 4 stroke of the combustion cycle. Intake, compression, power, exhaust.
It would probably take a whole book to explain the mysteries of the bump stick.
I'll do better later.
