ICRAZY6

iTrader: (68)

390 iron block
D1sc pushing 13lbs
317 heads
Brute Speed blower cam
1 3/4" pacesetter headers, no cat Y-pipe, Magnaflow exhaust.

I'm looking at 1 7/8" and wondering if there's much to be gained by switching to them from my 1 3/4" pacesetters? I know my boost level will likely decrease, but will there be more power made? Speed Engineering has them for $400.

Just seeing what everyone thought is before I pull the trigger.

If someone has a dyno comparison that would be helpful as well.

Thanks!!!

Bob@BruteSpeed

iTrader: (16)

I don't think the gains will be enough to justify the cost and hassle until you're running more boost than you are. Bob

Rise of the Phoenix

iTrader: (27)

On NA setups, switching from 1 3/4" headers to 1 7/8" headers have seen as much as 25+ rwhp gains. I'd think on a Procharged setup, the gains would be even greater.

Bob@BruteSpeed

iTrader: (16)

I never saw much of a difference in the lower end (cheaper) headers myself, unless a lot of boost was being used. Bob

Mike 02T/A

iTrader: (28)

I never ran 1 3/4" headers, went straight to TSP 1 7/8".
My exhaust also dumps before the axle, Kooks 3 inch bullet mufflers. Like mentioned, it might not be worth the money. I do regret not buying a stainless set like Kooks, etc.

Detoxx03

iTrader: (14)

1 7/8 for sure. A friend of mine has the little ones on his car and we have almost identical setups and mine makes more through the midrange and up top. You never know when you'll upgrade power levels so just get them from the beginning.

Blown06

iTrader: (32)

I'd put a 2" on it.

King23

iTrader: (4)

^^ this if your going from a 1 3/4 header, wouldn't it be better just to go 2" for later down the road if you ever want to step up to a f-series blower.

DavidBoren

2" primaries make sense for a boosted 390ci. I would run them if you can.

Blown06

iTrader: (32)

My .02

Header primary size/length is an important thing on an N/A combo as the scavenging effect can create some additional power.

On a blown application, scavenging is moot point. During valve overlap the boost or pressure on the intake side is just pushing additional air/fuel out the exhaust. There really is no such thing as scavenging in the exhaust system as there is never a depression in the exhaust system that is significant enough to help pull additional air/fuel into the cylinder during overlap.

In my camp, if the motor has a blower on it, use the biggest header you can fit/afford. There will not be any power loss anywhere by going bigger.

*Note: This theory of mine does not apply across the board as long as the motor is boosted. In other words.......boost from a turbo requires a whole different theory. I'm speaking only in terms of supercharged combos.

The Alchemist

iTrader: (19)

For $400, and a Saturday afternoon in the garage, it's worth it.

I ran 1 3/4 headers on my 347/D1 combo at 16.5psi, and made 760/700, but might have made closer to 800 if I had bigger headers.... is it worth it, maybe.

Trust me, I understand the debate. Right now I've had the same debate with myself over my intercooler for the past 4-5 months. I have a cheap ebay one, and could probably gain 2-3psi up top with a better one, but do I really need more than 860rwhp?

lmt0705

iTrader: (7)

Um.....yes! Lol. Who doesn't need more than 860???

The Alchemist

iTrader: (19)

Well, I'm at the limit of fuel system as well. So more power would mean a major upgrade fuel wise as well.

conan

iTrader: (5)

Often wondered how much my exhaust is holding back. 1-3/4 Kooks 3" off road Y and a Hooker catback. I've looked into Kook's 2'' header with their 3" dual behind them but its a pricey upgrade.

Blown06

iTrader: (32)

I really sat back and thought about this for you for like 4 hours. I decided that yes, you really need more than 860 rwhp.

The Alchemist

iTrader: (19)

Yeah, it's kind of like sitting at a bar 5 minutes before last call, 8 or 10 drinks in, and deciding if you need one more.

TXsilverado

iTrader: (18)

I have zero proof, but this is where my head is at. i'm pulling 1 3/4 off of my blown 408 for a 2" primary, 3.5" collector and dual 3.5" exhaust through bullets.

conan

iTrader: (5)

You plan on sharing your results when the swap is complete ?

ICRAZY6

iTrader: (68)

I would be interested in see those results as well.

TXsilverado

iTrader: (18)

sure, but it wouldn't be an apples-apples comparison. the current setup is 1 3/4 with 3" duals H pipe and I think 80 series flowmasters (bought it this way). next setup with be a straight through muffler with an X. not really a fair comparison. also 2 different dynos, 2 different tuners and more meth this time around.