Does anyone know if there are any Headers with D-Port opening? The L98 heads have a D-type exhaust and the headers I have seen for this year have round openings. Is there a header with D-type opening? Thanks, Sean

 

Run a search!

Hooker, TPiS both make stuff specifically for us.

 

I haven't seen a set of headers with a D-port opening. Would like to see a pic if they are availible.

 

It's been a while since I've seen a set but I believe Stainless Works' LT1 headers are actual D port. And since most L98s are D port too, I would think their L98 headers would be as well. Call them at 800-878-3635 and ask for Al. They currently have a forum GP going on so you can save some $ on a top notch header. Tell him what you need and I'm sure he can fix you up.

 

Still working on my overall plan for heads and camshaft but would like to start to work installing headers.

I called the guys at Stainless at the number given - they said for the L98 the special price was for normal (non-D port flange). Not too worried about the price - Need to know the difference and compatability issues with the different ports and headers please.

How good would headers with a D port flange work with the non D port (normal - oval?) ports. How would the oval work with D ports. Am guessing that if I got a D port flange it would work equally either way. Appreciate any experience in this matter. Thanks

 

Do NOT get headers that exactly match the exhaust port "D" shape.

The reason for that shape is the ledge serves an an anti-reverson barrier with little or no negative effect on outward flow. This minimizes dilution of the charge during valve overlap.

 

The Stainless Works set I received for my L98 in Sept
have a tall, narrow rectangular shape with rounded
corners. These are very nice pipes, see this and this
for more about how I feel about 'em.

They arrived on a Monday evening and were in place
by noon Tuesday. Since UPS kicked the box all the
way, most of the few photos I took were of the damage
to the packaging, but here are two that might help. I
used the FelPro 1406 gaskets (Brodix D-port
application) and recommend that you carefully check
any other gasket to be sure it doesn't hang into
the port - no matter what headers you choose.




.

 

It would be too bad if they do. The mismatch that a larger, round or square header port makes with a "D" shaped head port, provides an ideal anti-reversion step. Listen to 65Z01 on this one (as most).

RACE ON!!!

 

www.paceperformance.com. Page 8 in their spring catalog.

 

Think I understand the concept of minimizing dilution during valve overlap - but need to know if this occurs when the header flange overhangs into the head exhaust port (because it is smaller) or vice versa (when the header flange is larger overall than the header port). Sorry I don't know any fluid mechanics.

 

Smooth flow out, obstructed flow back in.

In other words, you want to be sure that the flange
and pipe are larger than the e-port.

For anyone who is interested, in the 70's a guy by
the name of (no kidding) Jim Feuling successfully
patented the concept of cones inside a primary pipe
that started with a flared/coned section at the flange.

His initial work was with VW's and then he worked
with Maurice Petty to further his findings and get
data on V8's. For a time, headers for SBC's were
available commercially. The idea also appeared on
one or more brands of exhausts for Harleys.

Probably due to the difficulty of building cones at
the flange, stepped headers were developed. Same
idea, just a less efficient/more easily packaged result.

Jim Feuling was no one trick pony. Besides serving
in the Special Forces, he also wrung more than 1,270
HP from a 121 ci engine and was a member of the
300 MPH club at Bonneville.

Mr. Feuling died due to pancreatic cancer in 2002.
There used to be a feuling.com website but it is gone.
To read more about this fellow's accomplishments,
take a look here at the salt flats website.

His 3-cyl Harley

His 1997 LSR-setting bike: 332/370 MPH

.

 

Sorry for being so slow:

"In other words, you want to be sure that the flange and pipe are larger than the e-port."

Wouldn't this mean that if you had D port heads, you would want a D-port flange? (am assuming the d port heads are "larger" at the squared off portion of the "D")

 

Nope.

While a 'D' shaped flange/primary that is larger than
the exhaust port opening in the head would create
a ledge or step, so would a round or rectangular
flange & primary. Each would probably serve in some
way to interrupt the reflected pressure wave travelling
back up the pipe toward the exhaust valve.

When you begin to consider practical matters like
the proximity of mounting holes to the port, adjoining
cylinders (3&5, 4&6 on SBCs), steering rack/box
intermediate shafts, upper control arms and so on,
you start making compromises and take what you
can get.

Frankly, Feuling gave reasons why a ledge didn't offer
much. IIRC, it contributes to turbulance that is
restrictive during outward flow and it offers nowhere
to divert the reflected wave.

His 'cone within a cone' created a venturi (the inner
cone) that aimed to have little impact on outflow and
a pocket (the gap between the walls of the inner and
outer cone) that formed a dead space the reflected
wave could compress into when it arrived back at the
lip of the inner cone.

The bore/stroke, targeted RPM range, valve size,
distance from the valve head to the port face, primary
diameter and length and so on, all factor into the
inner and outer cone design.

Of course, once you came up with the theoretically
optimum cone design, then you had to figure out how
to fit it within the physical constraints of the head
design and engine compartment.

Then you had to find people skilled enough to fab the
cones to close tolerances and others to build the
headers.

(In my case, I also had to find someone who could
replace primitive sheet metal layout software on
a Linde plasma cutting table with something driven
by AutoCad so that I could cut flanges for my BBC.)

Anyone with an interest in Feuling's patent for
anti-reversion headers might want to check out what
he did for themselves. In my community, I used to
be able to do inexpensive patent searches through a
federal science agency. I haven't had a need since
the rise of the Internet - bet you could probably get
your copy online, now.

.
.

 

Found it.

US Patent 4206600.