custom headers

[nismo kid]

this may be a really dumb question but what size tubing should i get to make custom headers ops: ? i have heard 1 3/4 and 1 7/8 and even 2 inches. if any one is wondering i am in the middle of going turbo if that changes anything. thanx for all the help guys.

[simply86T]

Monza headers (offered by Victoria British) are 16 gauge 2". Hope that can give you an idea.

[SteveZ]

nismo kid wrote: if any one is wondering i am in the middle of going turbo if that changes anything. thanx for all the help guys.

Does this mean your Building Turbo Exhaust Manifolds rather than NA? Answer that then I will answer your question

[nismo kid]

yep i'm goin turbo and i plan on making custom exhaust manifolds for both sides.

[SteveZ]

Well the Diameter of the runners really depend on thier Length.
As a General Rule of thumb the longer the runner the smaller diameter you want.
*When i mean smaller Im only talking small increments
The reason for this is to keep the exhaust gases concentrated and to lose as less heat as possible as the gases travel to the Turbo.

For exhaust Manifold Primaries on our motors I would 1 3/4" ID to 1 7/8" ID Depending on the design of the Manifold.

[G-E]

but you also have to keep in mind balance, if it's for a single turbo it will be tricky, you could end up going leaner on one bank due to less backpressure (see even shitty stock manifolds have benefits)

if you go twinturbo then I recommend starting diameter as close to the actual port opening of the head, and tapering open to a 1/4" larger diameter over the first 3-5" and collecting as parallel as possible into the turbo flange (tricky with only 3 cylinders into a rectangle but try anyway)

[SteveZ]

G-E wrote: into the turbo flange (tricky with only 3 cylinders into a rectangle but try anyway)

This is when some nice 3-1 Slip fit collectors come into play