wrenchtech

I've been thinking about trying to modify a passenger side manifold to install on the driver's side. Looking at the factory parts, I noticed that the I. D. of the factory crossover pipe is 1-1/2" and the outlet on the passenger side manifold is also 1-1/2". I might be able to hog it out to 1-3/4". If I ran a 1-3/4" downpipe from each manifold and merged them just before the catalytic converter into a 2-1/4" "cat and back" system using mandrel bend tubing, would I see enough gains to make it worthwhile? By gains I mean, reduced engine heat, better fuel economy and a small gain in power (not expecting much of that ;-) .

MaK92-4RnR

If you're planning on running factory manifolds, you could simply just fabricate a block off plate for the connection tube on the driver side manifold, and just run tubing from each manifold, create a custom y-pipe down lower at the transmission and run the catalytic converter there.

wrenchtech

Yes, I am seeing that the options are pretty much limited to an expensive header or a y-pipe setup with the stock manifolds. The outlet on the passenger side manifold is only 1.5" in diameter. So, now I am trying to figure out what size pipes to run from the manifolds to the Y (merge).

89fourrunner

Or, you could wrap the crossover really good and insulate it to death and save your money. Gains wont really be apparent anyway.