Header design

The 1UZFE EGR Delete Kit is available for sale here.

Hog Head

New Member
I need to have headers fabricated to fit a 3UZ into an old Merc and cannot find someone knowledgeable enough to design the header here in Thailand.
I have CAD drawings for the head flange and coupler flanges, but no idea about the optimal design for the piping

I see references to Pipe Max header design software for 100 USD
Any comments on ease of use and if this is the one to buy?
Can it allow for a blower?

Tri-Y or 4 into one for street performance in a heavy car?

Does anyone have basic dimensions for primary and collector tube OD and length?

Once the header is designed, the other part of the question is how to design from the collector back, resulting in a "system" rather than cobbled together components.


Super Moderator
Staff member
Sydney, Australia
I have 4 into 1 headers on my stock 1UZ engine but they were built for a prior supercharged engine I had.

I can measure the primary lengths if you wish and the diameter is way too big now and probably was when they were built.

I think people always go too big on pipe size, I think that's a guy thing. Bigger is better, thanks Tim Allen.

For instance I have a dual 3"system that only chokes down for the mufflers (I swapped the 3" ones for 2 1/2"as it was too loud. The car is way down on torque but I'm too lazy to bother fixing it as I have other cars to keep going and build.

As it's a 3UZ you won't be running big boost (I ran 21.5psi) so things like injectors and t/b should still support what you need.

As you're tuning it keep an eye on the duty cycle of the injectors and you will soon know if it runs out of t/b.

Good luck and keep us posted how it goes.

Hog Head

New Member
I have bought the 4T Wizard program and need help finding some data:

Exhaust port diameter and shape
Looks round, but my engine is in the car and difficult to measure ID

Hemi or pentroof combustion chamber

Cam timing For intake opening in relation to TDC, and Ex closing in relation to BDC
Not sure if or how it handles VVTI??