I have a stock LS with Crower 403 (stg 2) cams dialed in for hella overlap.
2-1/4in exhaust with Flowmaster muffler.
OBD0 B16 intake manifold with LS throttle body
Stock intake air box with K&N filter
3in ram air tube going up into air box

Up to about 7500 RPMs my MAP stays at or above 980. After 7500 MAP drops to 750. Am I right in assuming that my intake setup can't keep up with my airflow?

I really don't want to change my throttle body at this point and I'm not even sure that's my restriction. Would it make a difference if I change my ram air tube to 4in and change my intake tube (between the filter and the throttle body) to a smooth tube instead of the stock one?

 

if an engine cannot pump out what it draws in, you gain vacuum, the process slows down and are being counterproductive to what your engine and its current setup is capable of.

hella overlap? wth does that mean. close up the overlap and see what happens.

 

I don't understand this. If the engine can't pump out what it draws in, wouldn't the higher pressure inside the cylinder make it draw in less gases leaving me with less vacuum?


Sorry, I was lazy and didn't want to go out and check it. I've changed it a few times and don't remember where I left it last.

 

all gaining vacuum tells you is that you have a restriction....somewhere. just because your are reading from the intake, doesnt necessarily mean thats where your restriction is.

in a nutshell, if your engine cant execute what you are asking it to do, it doesnt and you are seeing the MAP pressure tell you so.

 

How do I figure out where the restriction is? How do I know if my intake is the restriction?

 

q16racer, can you point me to some articles about exhaust flow and air flow to explain what you're talking about? I'm just having a hard time understanding how exhaust restriction creates more vacuum on the intake side.