i work in a welding shop im wondering if anybody out there has any specs on how long should the runners and the size of the plenum should be for a gsr int.manifold im thinking of making one at the shop cause we do aluminum work too sow if theres anybody out there that could help me out would be great...

 

the length of your runners should be determined by where you want the car to make power. Compare a edelbrock manifold to a skunk 2 manifold. Shorter=high end longer=lower-mid range