I've read a bunch of information in the past on the benefits of long tube headers and resonance tuning depending on the length of the primary tubes and a little on how effective "stepped" header design really is for a street car application.

Could someone share some information or links/sources that have to do with the affect of increasing the primary diameter/steps on headers? How does this affect the powerband of the motor? Is it required to have a camshaft matched to the header design to gain any benefit?

Most people on the board go with 1 3/4" primaries, and I was wondering on a fairly aggressive stroker LT1 buildup, solid roller in the 250deg @ .050", 220cc intake runner 23deg head, is there a point at which an increase in primary diameter will begin to lose significant power? Any dyno tests done for this application? Thanks.

 

There is a thread in this forum named, "The Myth: Backpressure vs. Resonance Tuning".

Have a read through that. It contains links, literature recommendations and some good conversation.

Generally, a larger diameter primary is going to drop torque production
within the lower RPM range because exhaust gas volume (&/or velocity) is not
enough to create low enough pressure within a large exhaust
runner.

Needless to say, the larger diameter primary will be more effective
later in the band.

Cam/Valve timing is going to have a major impact on wave tuning.
Don't ask me how to calculate valve timing vs. exhaust lengths?

When the pressure wave reflects back and creates a lower pressure
region at the exhaust valve...it's at this point in time that the
exhaust valve should be opening (or fully open?). I believe it's
as the pressure wave approaches the exhaust valve, it should
just start to open.

When the low pressure area is present at the exhaust valve, and
the valve is open (partially or fully) it will help the exhaust gas
out of the chamber and also allow for more fresh intake charge
to fill during the intake stroke (during valve overlap).

That's the general idea anyway.