For a 550+whp car what Diameter should i go with. I was thinking either 1.5 or 1.625 ID tubing for the header. I think that 1.75 is too big. For reference the Ecotec Drag cars run 1.625. I am leaning towards 1.5" Weld els (usually mic to about 1.6 ID) I am underweight so the weight of the manifold wont kill me. I like the weld el's due to durability, heat retaining qualities, and price. I am planing on a equal length manifold for my new turbo. Ball Bearing T66 with .84 on the back with a P trim wheel. I am getting a fully ported and flowed head on the car plus some N20 to spool it. I am not too worried about the spool because of the N20 and the head is flowing good numbers with the porting we have done sofar. My only concern of the Weld el's is how hard it is to make a long radius with them.

Just wanted to get your ides on tubing diameter. I am expecting the car to be in the 700+whp range in about 4-5 months once I get some forged pistons, and some better cams in there.

550whp! Holy crap. on an sr20 motor? I've only heard of one on the dyno throwin' #'s like that and that was before the NOS kicked in. On Jamies car. Any way 1 5/8" is the smallest size tubing ever used as a header/ man. Even on a NA header. Are you serious?(SR20) motor.

Its actyally a JDM Mazda 2.0L very similar to the SR20. 86mm bore 86mm stroke. Stronger Rods and pistons than the SR20, better flowing head. Only downfall is iron block to the sr20 Alum. Keep in mind that this is not much of a street car anymore. It is a streetable drag car. For the NHRA street tire class. Only reason we are stopping at 550whp is the stock pistons. Once we get some forged pistons in there we are going for about 650 on stock rods. (keep in mind stock pistons and rods were cryo treated, rods polished, and pistons swain coated). The shop I am at has a Stock displacment DSM motor that made 640 to the ground with a 60-1 hi fi and a hundred shot.

Danny

1.5 is cutting that 550 WHP range tight.

1.75 is for the 650-750 WHP range.

15/8 pipe is the best size for your goal with a some good room for improvement.

Andreas Miko

12-16 inchs long will be the optimum length for that size motor.

Andreas Miko