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Just gonna make some headers...


Everlearn

Well-Known Member
TRS 20th Anniversary
Joined
Sep 27, 2019
Messages
99
City
Louisville KY
Vehicle Year
2003
Engine
4.0 V6
Transmission
Automatic
Well I’ve given up trying to find headers. I spent some time today drawing up a flange pattern based on the exhaust gasket. There’s a huge steel fabrication company right next door to my shop. I figure based on some other stuff they’ve made for me, they’ll cost about $50 for the laser cut and materials. I found 3>1 collectors and pre bent 1 1/2 exhaust pipe bits at Jegs. I figure all in all it’ll cost me less than $200 to make a set. If they turn out, I’ll have them ceramic coated. Now that I’m down the Offy 4bbl rabbit hole, I ordered a stage 1 cam from Summit. Pics coming........
 
I did the exact same build 9 or so years ago. I have a set of long tube headers for a 2wd truck hanging on the wall of the garage. the 2wd headers kinda hit the transmission if i recall. they have a hairline crack at the collectors. If i can help let me know. If you were closer id say just swing by and pick up the headers, ill sell them cheap. If you build the 2.8 you will be very happy with how much power it has, considering its age and size. I can break traction off the line with my truck and its on 38". I do have 5.13 in the diffs. but I have the duraspark II conversion, offy dual plane intake, holly 390, headers (for a 4wd) and 4 sp trans. I never post here anymore, just a super slow day. Hit me up 540-250-3537 if you are in the dc area and want these headers for a template or repair.
 
Man if I was close I’d come get. I have a fresh long block going in. Just got the offy intake and heads port matched. Could I trouble you for a photo of the header flanges?
 
Headers/exhaust manifolds are engineered to provide lower pressure at the exhaust valves on that bank at a certain RPM

The size of the tube and its length to the collector decides the RPM band for lowest pressure

The velocity of the exhaust traveling down the smaller tube as it enters the larger collector causes a pressure drop in the other tubes on that collector, lowering the pressure, this causes some of the exhaust to be PULLED out, leaving more power on the crank because it doesn't have to PUSH it out
It's called scavenged power because it's free/scavenged from exhaust velocity

This is also where the MYTH of Back Pressure came from
Car makers have been using this scavenged power since the 1950's
People would put larger pipes/tubes on the heads and then LOSE POWER

They would attribute that loss of power to "engine must need back pressure"
No 4-stroke engine needs back pressure, lol
What happened is they removed a scavenging/engineered exhaust manifold and lost that extra power

There are low-range, mid-range(stock) and high-range(racing) designs for scavenging exhausts

Even single "straight pipes" have a perfect diameter and length to get a scavenging effect at a specific RPM
 
Last edited:
Headers/exhaust manifolds are engineered to provide lower pressure at the exhaust valves on that bank at a certain RPM

The size of the tube and its length to the collector decides the RPM band for lowest pressure

The velocity of the exhaust traveling down the smaller tube as it enters the larger collector causes a pressure drop in the other tubes on that collector, lowering the pressure, this causes some of the exhaust to be PULLED out, leaving more power on the crank because it doesn't have to PUSH it out
It's called scavenged power because it's free/scavenged from exhaust velocity

This is also where the MYTH of Back Pressure came from
Car makers have been using this scavenged power since the 1950's
People would put larger pipes/tubes on the heads and then LOSE POWER

They would attribute that loss of power to "engine must need back pressure"
No 4-stroke engine needs back pressure, lol
What happened is they removed a scavenging/engineered exhaust manifold and lost that extra power

There are low-range, mid-range(stock) and high-range(racing) designs for scavenging exhausts

Even single "straight pipes" have a perfect diameter and length to get a scavenging effect at a specific RPM
How do I Find out what that is
I have a 90 2.3 l 5 speed. I created my own "straight pipe' I'm thinking I n
 
 

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