bfmgoalie
Veteran Member
These are the headers on my car. Notice how the pipe on the flange shrinks. What's that all about?
Headers
- Thread starter bfmgoalie
- Start date
It looks to me that is how they made it.
bfmgoalie
Veteran Member
I'm just curious if there was any specific reason for doing so. Never saw that before.
natzx7
Member
I believe I have the same ones. From what I can tell, it's when you don't need the tube diameter due to a milder motor, but need to match the exhaust port size at the head for better flow. Saves installation woes and space in the engine compartment. I've resolved this issue by ordering a set of 2 1/4" primary Lemon's headers for my next motor. 15 week lead time and $3000 ! 
No significant shrinkage... The ends are actually expanded
They were probably sold with a measurement on the expanded ends to make them seem like larger primary tubes.
They were probably sold with a measurement on the expanded ends to make them seem like larger primary tubes.
That's a stepped header design it affects torque and horsepower
www.performanceracing.com
PRI Tech: Stepped Pipes vs. Straight Pipes
While stepped headers may offer improved power and power band, some applications are nonetheless better suited to a straight design.
bfmgoalie
Veteran Member
The heads they're attached to are ZL1/L88 heads.
Yeah, I guess if they were stepped headers the tubes would get bigger as the distance from the exhaust port increased. But stepped headers was my first thought, too.
Increasing velocity at lower RPMs where exhaust flow isn't much limited is all that occurs to me as an advantage of necking the header down. But I would think that would limit higher RPM flow.
Increasing velocity at lower RPMs where exhaust flow isn't much limited is all that occurs to me as an advantage of necking the header down. But I would think that would limit higher RPM flow.
