avengedws6

iTrader: (15)

Ok Im considering a motor build for my t/a. What are some average starting horsepower numbers?

The Postman

iTrader: (44)

for a N/A 408?..depends on exactly what ur building...do a search on here and you'll find a thread that had 408 dyno numbers...

most ranged from 490-560 with some hitting close to 600 N/A...but there are A LOT of factors and options out there.

I'm working on mine slowly and hoping for around high 500's when its done....I'll be running spray on mine.

avengedws6

iTrader: (15)

what kind of cam have u been looking at?

TheBlurLS1

iTrader: (8)

If you're looking for all-out N/A HP, you're going to have to spend some money on heads, then you'll be restricted by manifold (I'm talking about the FAST). I see most 408's making 500-550 depending on head selection, cam size, and compression ratio.

Mine has Trickflow heads, PatrickG cam (242/246), 11.5:1, port matched FAST, and Kooks 1-7/8 headers. It went a flacid 127mph at the 1000' (rev limiter) in a 3900lb car, N/A. Now I have smaller gears and a nitrous plate on it, it now gets a boner on the bottle.

The Trickflows require aftermarket rockers (Jesel on mine), and they are already expensive enough. If I did it over again, I'd go forged 9.0ish:1 347 (or forged LS2) with cheap heads, stock intake, and throw a D1 Procharger on it. You can max the D1 out and make a bunch of power. Step to F1 if you get bored.

xhk651

buddy of mine has a 408... cheap heads, texas giant cam, ported 9090, 3800 stall 410s 9 inch turbo350 tranny.. lot of things that rob power.. and he was on a dyno that reads about 20-25 low on avg..

IIRC he put down 490

avengedws6

iTrader: (15)

Looking at the iron 408 with stg 2.5 L92 heads stainless steel valves, MS4, double roller chain and ported ls2 oilpump, ported 92/92, 4:10's, 6spd.

xhk651

go with a set of heads like trickflow or something equal.. a bigger cam than ms4..

TheBlurLS1

iTrader: (8)

I would NOT put 4.10 gears behind it. I went from 4.11 to 3.73 and like them much better. 127mph was 6800rpm max in 4th gear with 315/35/17's on the car. 1st gear was worthless on the street (still semi-worthless lol), and it would continue to spin the tires in 2nd. If you're actually thinking of putting those gears in a stock 10-bolt, you will destroy that bitch with the stock motor lol.

MS4 is too small for the motor, you'll need a custom cam to make those L92's work from what I hear.

You'll also need at least a hotwired Walbro 255 and some 42lb injectors BTW.

xhk651

ouch.. still on 10bolt..

id get a rear before i got a 408.. unless you never plan on using any of your power..

as for gears, i like 410s.. its preference..

like i said before, get something besides an ms4.. it is too small.. something like a texas speed giant will do good.. but not as good as a spec'd cam by pat or pred..

the walbro and injec. are a must.. you will max the injectors out and then some.. haha

Sluggish

iTrader: (10)

You will run out of gear with 4.10s. Unless your running 1/8th mile get a higher gear.

xhk651

thats where i run.. hence the 410s and 26 inch tire..

WizeAss

iTrader: (5)

Trickflows don't need aftermarket rockers... they recommend them. Many folks have done TFS heads with stock rockers and not wild cams.

I like the idea of a TFS Headed 408, 244/248 cam, 1 7/8 headers, FAST92mm, 90mm Nick Williams TB and a 150 shot via a NitroDaves TB Plate.

Good for 535 n/a and about 640rwhp N2O...... and a big fat smile! and money left in the bank.

WizeAss

iTrader: (5)

Seriously... if you get a L92 head on a 408, find out what RPM recommends on the cam.... they made a very nice improvement on my power from another sponsor's cam. Specs are in my sig.

Greed4Speed

iTrader: (7)

Nick,
Who are you looking at building it?

HP goes from 470 up depending on how wild you want it and how much $ you dump into it. Mine is making 481 hp and 470 lb/ft. Its a daily driver with full exhaust too. You heard it a BWW on Tues, did it sound like what it is?

I'm running my stock fuel pump and SVO 30lb injectors and I'm not having any fuel issues. This has been confirmed by 2 shops.

I agree, the MS4 is on the small side. My cam is a 240/244 comp grind and it feels small. Plus if you want L92 heads you really need a custom grind.

From what I've seen, L92's aren't doing any better than ported LS6 heads. Plus you are limiting your intake choices with L92's. I'm running ported 799's. Unfortunately they're not that good and are killing my top end. My HP curve levels off at 5200 RPM. The shop that ported them are local and a sponsor on here. They blamed the full exhaust which is dual 3" to 2 mufflers to 2.5" under the axel with a big muffler 2OTL, but it still did this with the exhaust dumped at the axel which is 3" all the way. Intake is a FAST 92/92, headers are QTP 1 7/8". If I had to do it again, I'd go with some aftermarket heads. Thats what I get for trusting the shop.

I also agree that 4.10's would be overkill. I'm running on 3.89's and I know of another stroker running 3.90's. You will kill your 10 bolt and you will need a good clutch.

aDaM Ws6

iTrader: (3)

I have a 408 heads/cam/intake/exhaust

Trickflows 235's
Custom Cam 248/254 .646 .646 112
90/90 FAST PORTED INTAKE AND TB
Kooks 1 7/8 headers, kooks 3 inch y pipe, magnaflow exhaust
I also got 4.10 gears

It did 575 rwhp / 505 rwtq OPEN HEADERS

Then through the magnaflows exhaust it did 545rwhp/485rwtq

GMCHammer

iTrader: (4)

Wow.... losing 30hp and 20tq with the exhaust on! Wonder what I could pick up with some cut outs.

Greed4Speed

iTrader: (7)

That's what I was thinking. Cut outs and gutting the cats.

Rapin'Ya

iTrader: (1)

If you want to make some real power, definitely DO NOT listen to Wiseass. He's been trying to go fast with his setup going on at least a YEAR now and still hasn't learned anything but how to swing from another shops nuts! Woo Woo!

phantomLT1

iTrader: (2)

It doesnt matter what you build Nick your still gonna get drug by the lil 383 LT JUAN

beardWS6

iTrader: (1)

iron 408, 250 255 640 640 113, ET 245 heads, 1 7/8 headers, ported fast 90, A4 with nitrous 3200 stall and made the numbers in sig rwhp 526 trq 489. My car rolls on motor but is tuned for the 200 shot that I have. Don`t ask what she does on spray, nothing but run its *** off!! My tranny and stall eat some power, I have 12-bolt with 3.73 gears and heavy wheels to boot. I have a SD tune and love driving her, very nice!