I'm getting ready to put my 468 back into the car, The headers I was using was Heddmans Elite 2" primary into 3" collectors, But they are pretty rusty and banged up. I have a new set of Hooker competition headers but they are only 1 3/4" primary into 3" collectors. What if any would be the benefit of the smaller headers. Its a Oval Port motor, 10 to 1, Solid 248*@ .050 .595 lift cam, RPM intake. I shift about 6200. Will I be giving up any HP going to the smaller tube headers? Thanks David

I highly doubt you will lose any performance/ET with the smaller tubes.In fact,you might pick some ET up

with a modest 6200 rpm shift point, the smaller is better deal applies for sure.

Ok guys at what point would you recommend 2" primarys my bbc will be about 625 hp with about a 6500 rpm shift point. Its a stepped on zz502. Ralph

I ran 2 1/8 on my 468ci last season. Have yet to run this season on brand new 2 in. and am curious to see if I pick up or lose et?! I would think 2 in. would be perfect for any 496 or larger engine. Your hp is similar to mine also.

Run your combo here:
http://www.headerdesign.com/

Ed runs 10.3x with 1.75 headers and scavenger collectors, 1.825 might be optimum, cubic inches dont decide tube size. Having said that,,, there was not much difference in e.t. with my old motor between 2" and 1.75" tubes, maybe a tenth or so, with the smaller tubes being quicker :) in automotive performance, unlike other parts of our lives, smaller is usually better :D

Wow i ran the design program and it recommended 1.8 primary size for a 625 hp 502! I'll have to give this some thought. Ralph

It's funny, some say its HP-based, some look at discplacement- while I'm no engineer, I am a math guy and it still seems that looking for a peak header torque at the bottom of the operating range is still the right math solution to header size. Example is a little L88. I'd NEVER run small tubes on a 427 that works from 4500-7200. Yet, the 2" pipes are too big for a 468 that never sees above 6500. Anyway, smaller is USUALLY better. Yet, I run a HP-based mill that gets spun up and 2" with big collectors is the deal.

I'm not recommending big tubes here, just illustrating an exception to the rule to keep everyone's mind open . But y'all don't build 7000 rpm HP mills for the street anymore , do ya!? Call me " Stuck in 1969! " :) with today's OD trannies, its easier than ever!

The optimum for racing is obviously different that street use where just getting good free flow makes all the difference. One thing to keep in mind, you will want to check, but I don't think the Hedman Elites are equal length. They are a nice durable header that installs without hassle (I have them in the 1-3/4" size for the 408CI motor). In order to get true equal length, pretty sure you will have to get 2 pc. primary tube design.