VictoriaVette

I know Comp cam says the 270H cam is from 1800 to 5800 rpms but it does not start pulling good until over 2500 rpm in my 77. I guess the 3700lb vette hold it back quit a bit.

jetnoise

Advancing or retarding your cam will be fruitless until you know where it is at right now. Dot to Dot is in no way acurate but serves many people just fine...but if your looking at advancing you need to know.
Opening the intake valve sooner will most likely put your intake valve closer to your piston so you should check ptv clearance while doing this.
You need a degree wheel to determine where your valve events are at. You will also need to be absolute in determining tdc....don't go by the timing pointer. Comps Cams do usually have 4 degrees already ground in them.

I would also investigate you are using the correct length pushrod. Any changes in cam or rockers or heads or valvetrain components can alter what it needs.
Incorect pushrod lenght =dog
The way I like to check stall speed...crusing in high gear, below what you think is your stall speed, maybe somewhere between 30-40 mph depending on your gears, mash the gas and watch your tach to see how high it goes instantly....this can be effected by how accurate you tach is too. The foot braking method will not give you an accurate true stall

my .02