Someone school me on header size.

[Killer6]

Sounds like a killer engine.

Yeah, He got it tuned in pretty good, that mill cc'd at 9.69:1 static squeeze and ran pump premium. He replaced the 340 about 3 years ago w/a 408 & Indy LA-X heads, still
runnin' the 6bbl. ................

 

[MOPAROFFICIAL]

Your builder, your deal.

This what happens when you don't discuss the plan before pulling the trigger.
Over engineering time.

 

[Mattax]

How do I go to battle with a well known mopar engine builder over this?

“Hey man I know you have built thousands of wallet winning engines over the year and dyno tested countless small blocks but my buddies online say to use a different set”

It may not be a battle. Once it is clearer what you want to do, you can collect header specs from a variety of well respected sources. Then go over it with your builder and there may be no objection, though maybe a good discussion.

Here's some good ones:
Elston Headers: Calvin Elston builds everything but is probably best known in the Winston Cup Nascar world.
Basic rule of thumb from his blog: What tube size off the head?
He's also been an active participant at Speedtalk, so much more there. This is a good one to start with
"What is [exhaust] Blowdown Length?" p.2
Burns Stainless: Fill out the form and they will provide design parameters. Used by many top builders.
Headers by Ed: Fill out the form and Ed Henneman will provide a design parameters. A little more old school than Burns. Ed's focus is equal length 4 in 1 designs mostly for 1/4 mile.
Pipemax: Purchase a copy of this very reasonably priced program from Larry Meaux, fill in the information and it will provide the recommended header specs. Larry has his own forum but also participates on Speedtalk. He's an engine builder first and foremost.

Any one of them will put you in the ballpark. All will require either a little or a lot more information than you've got so far. That's why I don't think your heading toward an argument. This guy may have said what he thinks of your situation based on something he gathered from your call. Without the cam and rpm range, there's not much to discuss.

i just spoke with a very reputable engine builder about headers for my 360. It is a .30 over 360 with flat tops, undetermined cam, performer rpm intake and Holley 750 dp.

The builder says if I go smaller than a 1 3/4” header I will be hurting the optimal power output. It looks like TTI makes a 1 5/8” x 1 3/4” stepped header. Would this be what he is referring to?

 

[MOPAROFFICIAL]

I think 1 5/8 would be fine for your application. My 408 made 485 hp and 511 torque with 1 5/8 headers on the dyno.

Would you be okay with sharing the combo?

 

[MOPAROFFICIAL]

Fart

 

[grimreaper]

try this....
Primary Header Tube Length and Diameter Calculator

 

[doogievlg]

I went with the tti headers. 1 5/8 stepped to 1 3/4

 

[QuickDart360]

The TTI headers are nice! They will work great. Have fun!Any vam specs? Solid hydraulic?

 

[doogievlg]

The TTI headers are nice! They will work great. Have fun!Any vam specs? Solid hydraulic?

Hydraulic roller.

Duration is 235/249 at .050” lift. Lift is .522/.509 with a 107 Lsa.

 

[QuickDart360]

Sounds like a nice muscle street grind!

 

[68Dart500]

Would you be okay with sharing the combo?

10.1:1, unportef Edelbrock heads, comp cams roller rockers, Edelbrock air gap intake, 750 double pumper, oh and a Howard's 290/295 cam with .575ish lift