exhaust manifold

[Brian]

I've been told that a rotational firing order into the collector would be ideal? 1-3-4-2 should give the most scavenging, and therefore most hp and tq.

TRD has a LHD header for the ae86. The old style was 4x2x1, the new style is 4x1 but doesn't have rotational firing order either?!?!?! OBX makes a stainless steel copy of the TRD 4x1 header. However, the last one that I tried installing had a flange that wasn't flat, and cost a lot of $$ to have machined flat.--it cost 4x more than planing a cast iron manifold.

Vibrant is developing a stainless 4x2x1 header that is rumoured to fit the 16v and 20v heads--same header, dual-bolt-pattern flange.

Technopro Spirit has a header, but it's hella expensive and made of mild steel with some sort of high-temp paint.

Pacesetter headers are functional, but the design is not durable. When compared to the old-style TRD, the pacesetter has the same piping diameters, etc, but does not have the formed steel collector flanges. I've seen several broken Pacesetter headers.

To diagnose your existing leaky manifolds, simply use a piece of vinyl hose, and put one end in your ear, and the other end close to the manifold joints. You will be able to distinctly hear where the leaks are coming from.

HTH.