evil, I'm not sure what you mean by inlet risers, but as for spacers, like you said, they're a great tuning aid.

It all depends on what you want from your motor and where you want the "sweet spot" of torque peak or horsepower peak to be. When advising on spacers and manifold volume (180 versus 360 manifolds), if the motor is for a fairly heavy street-driven car with a stock converter or slightly higher stall converter, I'll always recommend a 180 manifold and 4-hole spacer to build max torque at a lower, street-useable rpm. In my opinion, it's a matter of creating a strong negative pressure in the manifold to increase velocity and maintaining a homogenous mixture, minimizing fuel separation.

With any manifold manufacturer and Edelbrock in particular, you can read the characteristics of the different manifold designs on their website.
http://www.edelbrock.com/automotive_...lds_main.shtml

In spite of this information, there are neophyte engine builders who will want to use a Victor manifold on their warmed-over street motor. Or they'll choose a RPM variant of a 180 manifold. I guess they think that the higher rpm manifold will magically turn their cam-limited motor into a fire-breather.

Back to spacers. Again, in my opinion, if you are building a mild street motor with a 180 manifold, use a 4-hole spacer and experiment with spacer height. Using an open spacer will turn your 180 manifold into a 360 (open plenum) manifold and move the sweet spot higher in the rpm range, away from streetability. Now, of course, if you are looking for a street motor that makes power higher up, by all means use a Torquer or Victor intake and stack open spacers on it 'til hell won't have 'em. But you had better back the 360 manifold and spacers up with the proper cam and that means the proper valvetrain and the proper converter and the proper rear gear.

99% of the first time engine builders out there will be better off with a reasonable compression ratio, mild cam to match the compression ratio, 180 manifold, 4-hole spacer and mildly modified stall in the converter. Like I've said from day one, everybody starts from the wrong end of the car. The first thing you need if you're wanting to build a fast car is a stiff rear gear, then a looser converter, THEN go-faster goodies in the motor.

We've all seen dyno tests by magazines where they mount open spacers on a 180 manifold and it's true that they'll make a little more horsepower and torque, but take a close look and you'll see that it's at a higher rpm level, away from where you want your street motor to pull hard.

COMBINATION of parts is the key to any build, figuring out exactly what you want the car to do and choosing the proper parts to get there.