WickedC5

iTrader: (3)

I currently run 1 3/4" Long Tube Headers on my forged 347/F1C, pushing ~19psi. Would 2" LT's be too much on a 347, or would it work well, since it's on a F/I set-up making ~800+rwhp???


TIA

skyhighsami

iTrader: (8)

I'm curious about this as well

wilson34

iTrader: (7)

I'm going to be running some 2" headers on my car w/ F1C, but I'll be around 400cubes

ericg69ss

It depends on your goals and application. We are learning that blower combo's need bigger exhaust than you would think. It is important to note this is based around all out drag racing applications. With bigger headers you may suffer a drop in power/tq in the lower rpm bands. If this is a street car you are probably fine with your 1 3/4". If it is for all out drag racing I would consider putting the 2" headers on.

I'm running a 410" motor with a gear driven F1C and we are going to build a set of 2 1/8" stepped to 2 1/4" with collector mufflers. For us our engine lives between 4500-8500 rpm so we were not concerned with what happens at 3000-3500 rpm.

Hope this helps and good luck!

WickedC5

iTrader: (3)

Thanks for the feedback guys. I've got 3:73's and a 3600 stall, so I would think that should keep the car pretty responsive down-low in case of any power/tq loss in the lower RPM's. I know not too many people are running 2" LT's w/ a 347, but there are quit a few running 1 7/8"...

ericg69ss

Sounds like you should be fine. Do you drag race the car at all? If so do you use a transbrake? Sounds like your converter will help out. Our converter runs a bit loose and our datalogger shows the motor going from 3500 rpm off the 2 step to 6000 rpm in about .02 of a second. Boost PSI was 8lbs at 3500 rpm and 19lbs at 6000 rpm. From 6000 rpm to 7500 rpm our average was 20.8lbs of boost.

WickedC5

iTrader: (3)

I try to get out to the strip a few times a year, but the car is mainly a street toy. Just looking to make it more efficient. The converter is a PY3600, so it should be pretty tight and not slip. Looks like you're pushing a good amount of boost as well..got to love the F1C

Thanks!

Blown06

iTrader: (32)

I'm gonna be trying 2" on my iron 347 with an F-2. My opinion is that once you pass the 15 psi range on a stock sized blown ls1 1-7/8 stepped to 2" or just 2" is the way to go.

fatmat80

I run 1 7/8 ARH on my d1sc 347. If I had a f1c on it I would definately run the 2 inch headers. Good luck..

eb02z06

iTrader: (18)

I wouldn't waste my money on a 2" header unless your starting from scratch. The biggest bottle neck is the 3" mid-pipe section and 3" collector. Until they make a 3.5" collector I won't be changing anything.

BTW-the 2" requires some massaging if your running a aftermarket bellhousing.

WickedC5

iTrader: (3)

In regards to the install of 2" headers, I've heard the same about it being challenging...Someone said they had to drop the cradle, and make some cuts to squeez them in there. If it knew for sure that they would get me another ~25-30rwhp, I wouldn't think twice about it. We'll see...

Blown06

iTrader: (32)

My 2" kooks have a 3.5" merge collector. Had to cut the ears off the tranny and clearance the frame. 2006 truck.

WickedC5

iTrader: (3)

How are the 2" headers working for you on your setup, 346ci according to your sig?

Blown06

iTrader: (32)

Should now within the next month or two, haven't got it running yet. It's a "I'm gonna get flamed combo on this site" but we'll see how it works. If it doesn't, I'll build another motor for it.

Iron 346, ported 706 heads with cometics and ARP bolts, cog driven F2 with A2W. Sounds dumb, huh? Gonna start with a 77/54 pulley combo to help it survive. Sorry for the thread hijack.

Back on topic please.

WickedC5

iTrader: (3)

Nothing wrong with thinking outside of the box. Post results when done.

98Z28CobraKiller

iTrader: (17)

Do it.

JUICED1

iTrader: (3)

I'd go 2" at that point. If you decide to add more boost down the line you'd regret not having them. ARH makes a nice set!!!! Check out the group purchase page.

blk00ss

iTrader: (66)

If this is in an fbody, there is no massaging required, and they come in 3.5" collector.