Your exhaust is way undersized . I thought mine was fine hahahaha
Plus those flowmasters are restrictive too .

With a blower forcing all that air in , it wants to get the hell out , NOW ! , not the same rules as N/A stuff , you dont need all that scavenging bullshit , Forced induction breaks those exhaust rules that we've all been used to , high boost blowers to put it better .

And make sure you didnt miss my post above , where i said even with the 3.5" cutout OPEN i still had 20 psi backpressure . Ive got an angry little setup . Cant waith to see how it will do with these bad boys .

 

Would be nice to see someone do a before and after on the Dyno.

I think people would better understand that.

 

an H pipe, That's old school. Haven't seen any one do that in a long time...

 

It wasnt my idea. The bad part is the guy that built the car owned an exhaust shop! He didnt know much about ls stuff though.

 

at 12PSI youre flowing a lot of air, but its not night and day more than others are.

I run 15+ on my 370 with more cam. Not that its apples to apples by any stretch, but your 408 has 10% more displacement than my 370, but I run 25% more boost.

Your restriction is not in the dual 3" pipes or the headers, its in the flowmasters if at all.

 

Tims back pressure was unchanged between cutout open and closed. The restriction was his small headers. Stew I don't think you'll see near the back pressure you think.

 

Yes , it was , hence the creation of this thread

Bigger is better with high blower boost in my application, but i cant think with 12psi on a 408 you "wouldn't "want bigger pipes .

Edit **

 

Didn't read all the threads, but I'd like to know if there's any issues getting to the plugs or wire issues. Fixing to be spraying as much nitrous on my truck as it makes on motor and Id like to get these. How much were these?

 

the difference between me and others is that 12 psi is the lowest boost my blower will run....I'm on a 4" pulley and would like to pulley down at some point and need to get my ducks in a row. and you guys know me. I don't like to half *** anything. I cant wait to see the results from this swap. I'm taking notes and learning this boosted world.


so If I was to buy new headers I might as well get 2" with 3.5 collector...but since I already have the 1 7/8 and 3" I might as well just ditch the flows and be happy?


is there a such thing as cutting off a collector and welding in a larger collector?

 

who stops at 12psi?!?