When does primary header size matter?

[Trackman]

I am about to order the hotside from CG and am wondering at whet HP level should a person consider 1 3/4 primaries over 1 5/8?
I'm using a 76mm turbo and have the motor built to handle 30lbs.
100% drag car with high 8 goals.

 

[BLU3VN0M]

I think either will be fine; personally i'll be running twin 64/65's with custom 1 3/4" primaries.. I figured I might as well get it out of the way.

 

[Woody6799]

I would go 1 3/4. I researched the hell out of mine when I did it and found that sub 700 1 5/8 is great, anything above that is 1 3/4. Being that it is a drag car 1 3/4 should be your answer

 

[Trackman]

I guess I'll drop a little more cash and get 1 3/4 and be done with it.

 

[Nightmare302]

It won't matter, my opinion is keep the header size as small as possible to keep up flow. This isn't an N/A car and therefore won't react the same. I doubt there would be any change in power between the two and better spool on the smaller size.

 

[Nightmare302]

Factory manifolds have made well past 1500rwhp. Food for thought.