Got my CAT headers today. They look pretty nice.
The primary tube diameters vary from ~29" to ~33" and the average length
is ~31". This is a bit longer than Ricks headers that vary from ~26.5"
to 31.5" with an average length of 28.5".
The primary diameters of the CAT headers are 1 5/8" OD Vs. 1 1/2" OD for
Ricks.
The CAT headers have a merged tube type collector with a relatively
steep taper of ~12 degrees. Ricks headers terminate in a baffle type
header with no real taper other than for a short distance just past
where the primaries merge into the collector.
The CAT headers have a collector diameter of ~2 1/4", Ricks are ~2 1/2".
I can see that the CAT headers are designed to give more clearance near
the oil filter area and I am hopeful that I will indeed be able to run a
shorty filter directly on the block or at least be able to use the Ford
Racing/Econoline 90 degree filter adaptor.
I'll post some pictures of the two header types for comparison tomorrow.
Warning! Editorial comments to follow!
The collector design of the CAT headers is superior to the collectors on
Ricks headers. The merged tube design used on the CAT headers has
inherent advantages over the baffle type collector used on Rick's
headers. The fact that Ricks headers have no real collector taper makes
matters worse. I noted that the taper of the CAT collector is fairly
steep and I have read that a less steep taper (10 degrees) would be more
effective for lower broader RPM ranges relative to steeper tapers.
The merged collector promotes less flow turbulence because of the smooth
transition into the collector. The merged collector design relies
primarily on inertia effects for scavenging and the flow enhancements
of this design are conducive to this.
The merged collector design reduces the effects of resonance tuning.
This is good and bad. Resonance tuning can both help and hinder
scavenging depending on the RPM range of operation (and cam timing and
gazillions of other effects). A merged tube collector won't exhibit as
many bumps in the torque curve compared to a baffle type collector
because of the reduced effects of resonance tuning.
The primary tube diameter of the CAT headers is also better suited to
larger displacement and higher revving motors as compared to Ricks
headers. The converse of this is that Ricks headers may be a better
choice for a stock or mild 260.
The effects cited are normally pretty subtle and probably do not matter
much for the daily driven non-competitive Tiger. Header science is
non-exact (except for those with lifetimes of knowledge and big
computers) and the comments here are general and made by someone without
a lot of practical experience with a wide variety of header designs so
caveat emptor. I have read that the best practical way to decide what
is right for your combination is to spend a lot of time on the dyno with
a lot of different types of headers. Like that is going to happen for
most of us! Just passing on some things I have learned.
Frank
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