theformula

Why does SLP tell the 350 guys to get the 1 3/4 headers. The 91/92 350 Firehawk had 1 5/8" headers...and it was HEAVILY modified! And it ran low 13s..!

------------------
91 Formula 1LE 1 of 46
305 TPI 5speed
1LE/G92/WS6

Paxton SN92 supercharger, Ford SVO 24#injectors, Crane AFPR,SLP airfoil, ported/polished plenum, March alt. pulley,Crane Gold 1.6rrs,MSD coil,MSD6AL (5400rpm limit),Holley 9mm wires,Ac delco R43ts plugs,custom chip,Bosch O2sensor,SLP 1 5/8" headers,SLP catback,shortened shifter,3:73s w/Auburn posi,180* t-stat,JET 195* fan switch, Macewen white face gauges, Autometer gauges, Zoom hi-performance clutch.

[This message has been edited by theformula (edited April 14, 2001).]

IROCZTWENTYGR8

iTrader: (1)

I don't know why they put 1 5/8's on that car, but I know that 350's, especially heavily modded 350's, work much better with 1 3/4 headers from seeing dyno results and 1/4 mile improvements when switched to them.

[This message has been edited by IROCZTWENTYGR8 (edited April 14, 2001).]

theformula

I dont know. SLP is the one who made the firehawk and the headers. YOu figure they know what they are doing... Who knows

IROCZTWENTYGR8

iTrader: (1)

It sounds to me like they didn't want to make it "too" fast for a car like that, because they had to know that it would have been even faster with some 1 3/4's.

[This message has been edited by IROCZTWENTYGR8 (edited April 14, 2001).]

IROCZTWENTYGR8

iTrader: (1)

[This message has been edited by IROCZTWENTYGR8 (edited April 14, 2001).]

BigMike 92 Z28

Maybe they dident have them out at the time or they were too much $$. Also from what iv always herd is that 1 5/8" to 1 3/4" headers is maybe 2-3 horse if lucky on a modified 350.

------------------
1992 Z28 W/5.7L. Teal with unpainted cowl hood,18" Billet Specialities Rims,Eibach Sportline Springs, Leather int., B&M Mega Shifter, Headman Headers, Flows,No Cats,K&N,HyperTech air foil,Custome Burned Chip,MSD Ignition,Shift Kit, Billet Corvett Servo my Back License plate reads "ALL UL C"

Here's a couple pics of my car

http://www.geocities.com/jonnyarson/maro.jpg

http://www.iroczdesigns.com/images/camgf.jpg

http://www.iroczdesigns.com/images/cam5.jpg

[This message has been edited by BigMike 92 Z28 (edited April 14, 2001).]

theformula

Theyre usually the same price, and I'm pretty sure they had them out then. I doubt they didnt use them because it would be "too fast". They wouldnt of modified everyother part of the if that was the case

black5.7GTA

I dont know as well,because the 91-92 dealer installed package had the 1 3/4 on the 350's.Anybody know if the 4 aluminum 383 had the 1 3/4's?

------------------
1990 Trans Am GTA,Black/Black Leather,350,auto 3.23,Dual Cats,
SLP Package,SLP Torque Converter/Shift Kit,Fastchip,GSC's
G-tech 0-60 5.1 1/4mile 13.6@104
member www.transamgta.com
Previous Thirdgen
1986 Camaro IROC-Z

IROCZTWENTYGR8

iTrader: (1)

Yeah, hehe, I know it most likely isn't because it would be too fast, j/k anyway!!

TRAXION

I ran 12.2@112mph NA with the 1-5/8" headers. I know I know - I should be running the 1-3/4" headers. I got a good deal on these headers a long long time ago. No biggie - I have a set of Hooker 1-3/4" longtubes sitting on my shelf

Just wanted to show what these headers can do. The biggest restriction in this setup isn't the primary size - its the collector size. 2.25" collectors freakin' suck!

Tim

------------------
TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

PETE

iTrader: (1)

the difference is not where you think you cant look to compare horsepower numbers between the two because they are desiigned for two different things.1st 1 5/8 headers make it easier for tourque to buiild on the low end because velocity is kept high with smaller tubes however once you meet a certain rpm that small tube which help velocity out when the engine wasn't spinning very fast now becomes a resrtiction at higher speeds where peak hp numbers are achieved that is why slp used 1 5/8 headers because their induction setup the t-ram was still a tuned intake, designed for tourque.

Ed Maher

/me raises hand

I'll bet you a dollar that SLP used the 1 5/8 b/c they are || that much easier to change plugs on (from what i've heard, could be wrong.)
Even though they were extremely limited production i bet they still usd the fact that dealer service monkeys would have a fit over the 1 3/4s.

Ed Maher

btw, tim, you still have your XR262 laying around? You have a future home for those SLPs yet? They'd both go well with the 3.73s that my sick little mind is thinking of...

theformula

I beg to differ on the plug changing of 1 5/8s. Holy hell what a nightmare it is changing plugs. I almost hired a little migrant worker to do it.

Ed Maher

Right theformula, the 1 3/4s are even worse than the 1 5/8s, thus i bet SLP used the 1 5/8s cuz at least a human can do 'em.

FlashGTA

In a recent header test 1 3/4's headers only made 4 - 5 HP more than the 1 5/8's. Personally I went with Hooker 1 5/8's and I don't have trouble chnging my plugs.

TRAXION

Ed,

I already sold my cam. The Headers are a different story. I am not sure what I am going to do with them yet. I might save them for emissions purposes ... not really sure.

Plus, it will be SOME time before I switch to the long tubes. It is just sooooo expensive to run long tubes. Headers, Coating, 2 Y-pipes (offroad and catted), Mufflex 4", and having Denny at Mufflex do the fabrication will run me almost $1900. Thank God I already have the headers. That's $400 off my bill.

Tim

------------------
TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

Kevin91Z

iTrader: (1)

On a stock engine? I'd believe that. The stock TPI cam and heads arent flowing enough air to need larger headers. But I just dynoed my car and gained 35 HP and 37 TQ at the wheels by switching to 1 3/4" headers. (no, not JUST the headers) See my thread on my Dyno Results.


------------------
West Coast GM Shootout 2001!
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

jimbo

...the SLP Performance Package came with the 1 5/8" headers...at least mine did. If you remember that the Firehawks were designed for the SCCA race circuit, it could be that the low end torque the 1 5/8" headers gave you was more beneficial on an SCCA road course than the high end horsepower you got with the 1 3/4's...

...for a car that was primarily a street racer with limited strip use, I personally would stick with the 1 5/8's...

...not that I race on the streets, mind you...

------------------
jimbo

Mosquito Coast F-Body Association (MCFBA)

1991 Formula SLP350
1999 Trans Am Firehawk

dhirocz

iTrader: (2)

I RESENT THAT!!

scooter

iTrader: (11)

Ummm I have th SLP 1 3/4 headers and I only have a problem with 2 plugs. If I had shortie plugs it may be easier. Right now I can get the 2 in by hand and then just snug it up with a wrench. Not bad at all, took me like 15 minutes to do all 8. Oh and Ed, I got Tims old cam. I may be interested in getting rid of it. if you want to make me an offer just email me...... I wont be using it for a long while now and I could use the money.

James

------------------
If the women don't find you handsome they should at least find you handy
88 GTA Notchback with 91 gfx and ROH Snypers
Aftermarket T-56 (pain in the A$S but worth it)
Lots of things to do still