Tdc

[syrushcw]

Ok I havnt seen anyone with the BC stage 4 288/288 cams but when my #1 piston is at top dead center my exhaust as to valves partially open. The pins are at 12 o clock, is this just because the cams are alot more aggressive?

 

[TunaTalon]

The area around TDC where exhaust and intake valves are both open is called the "overlap" area. See figure 30 of http://www.kidzuku.com/StrokeOrNot.pdf for the overlap area of other 4G63 cams.

And yes, more aggressive cams tend to have more degrees of overlap. At higher piston speeds the inertia of the air streams tends to keep the flows going in the right direction. This also gives a clue why aggressive cams run rough at idle.

 

[syrushcw]

TunaTalon thats a great article thanks