I know the swap to 1 7/8s are worth some power, and is simply a no brainer on a 10psi 427, but what are youre guesses on power gains from the swap only?

Taking into consideration I have crappy 1 3/4 SLP "so called" long tube headers which arent anything close to being longtubes, more like medium tube length 1 3/4 with 2.5" merge collectors.

I already ordered ARH 1 7/8's, 3" collectors, and will have them ceramic coated with some high industrial type of ceramic coat.

 

What kind of exhaust are you running behind the current headers? You could benefit from a 4" exhaust without a doubt...

I'd say the swap along with a pulley to gain back the boost you lost with the new headers could be worth as much as 40 HP... prolly more on a set up as extreme as yours.

 

I have a true dual 3" with an x-pipe and straight through mufflers after the crappy headers.

Assuming I dont pulley down to re-gain the lost boost (which I WILL btw, just want to take that out for the sake of the argument), I wanted to know how much power should I expect from the headers alone, and a re-tune?

all ears!

 

just guessing here id say about 15, and you dont need a 4", 3" is plenty if its straight through

 

I dunno...Nelson ran his 632bbc through dual 4" pipes... That 427 on 10psi probably isn't making the same power, but I bet its close.

 

I think what he meant was 4" y-pipe, but since I have a dual 3" exhaust, that covers it up!

 

Exactly... no way you should run 4" duals. Your 3" duals have it covered assuming its all mandrel bent. If not ditch it.

The 2.5" collectors are really choking you. I was conservative with my 40 HP estimate with the pulley included. Your headers are designed to toush nowhere near 800 HP at the wheels. People make good gains swapping to the 1 7/8" headers on a decent NA build thats 350 HP shy of yours. Even though you will lose boost, there will still be more fresh air entering the cylinder which can only help power. Headers and tune alone is a tough call... but all in this is DEFINITELY worth it for you.

 

well im no where near 800rwhp, its more like 800bhp.

I did order the headers, having them ceramic coated, and will also swap out the pulley and change my stock LS3 head for some big bore MAST heads, im hoping for like 50rwhp in total.

 

Are you kidding?? MUCH better headers, MUCH better heads, and a pulley swap to keep up with it all and you're hoping for 50 HP? Assuming the blower has more left in it that sounds like a recipe to take this build to a whole different level. Hopefully your bottom end is strong...

How much boost are you running as is? You seriously must be close to the end of where that TVS can take you after these mods...

 

man im trying to be conservative LOL.

Ive been told the heads alone will do about 40

pulleys about 30, since I think im pullying for 2 more psi.

and 10-15 from the headers.

Im at 8.5ish psi right now with the 10.85:1 CR built 427.

bottom end will take it, I feel bad for my built 6l80.

In total I think boost will be about 10psi. a TVS2300 should take 12psi on a 427, but im not trying to squeeze the life out of the poor blower.