Gordon0652

iTrader: (4)

So this winter i am going to start my turbo build. And i want to lay down about 850-900rwhp using the 6.0 manifolds on the track (93 hopeing, and meth!) and about 550-600rwhp on the street (93) through a TH400.

I plan on doing the trubo on my stock engine (about 500rwhp) for about a year until i get enough money for the 408 and TH400.

I am going to be building a 408 8.5:1 using TSP L92 heads.
-Cam: 223 in. 227 ex. 636, 639 115 Lobe Seperation 113 Centerline.
-JGS 50mm WG
-JGS 56mm BOV
-ST80 AR 1.1 T4 (Gonna spool like a bitch outta hell on the 408)
From what i have been reading on the board is that for a trubo that size i would need to boost like 25psi to get my track power. And that might not even cut it even with the meth.
(i have my fuel system, rear end, and eletronics all worked out already)

Any suggestions? I really had a mind set on this build and now it seems to be falling apart... I guess that i am thinking is that 25psi is very high and i wanna keep it as safe as possible to the engine.

Please help and comment if things need to be changed. I need all the input i can get. I keep geting mixed answers.
Thank you for your time!

98turbls1

iTrader: (17)

Well I'll give you some of my opinions... I think that 25psi (being that you have decent flowing heads and nothing really restrictive) is way more than enough to put you in the 850-900rwhp range.. I believe that Speedinc put down that much or a little more behind a th400 with a 370ci... I believe that you're putting way to much thought into it.. There are plenty of people that have been there and done that.. find one of them, decide what you like from their build, and see if there's anything that you don't like.. Building a car is kind of like making a masterpiece.. And in art there is no better compliment than immitation... Also if you're dead set on the 408ci than do yourself a favor and get a bigger turbo... It would most likely be choked off a little... From what I've seen that turbo would do a little better on a stock cube or a 364-370ci give or take...

P.S. i think that the 93 and meth should be fine if you keep your KR in check and should be just fine on the 408ci...

Gordon0652

iTrader: (4)

Bigger turbo... Meaning something like a S91?
I saw someone with an S91 and i think with a 402 and pushing like 25psi and only making like 750rwhp...

98turbls1

iTrader: (17)

Huh??? That seriously doesn't sound right at all.. You sure he didn't have like 6 plugs hanging out???

https://ls1tech.com/forums/showthrea...light=speedinc

Check out the speedinc car.. I know that it's a TT but you get the idea.. This is only through like 20psi...

SuperZ

iTrader: (2)

A 402 with a S91 and 20psi or more would be Over 1000rwhp

MonochromeSS

iTrader: (1)

Yep. Even if you play the ratio game and say a stock ls1 puts down about .85 hp per cube to the ground a mild 402 (a "stock" 402) should put down around 360. and 25 psi boost is about 2.7 times the standard atmospheric pressure. So that yields about 972 hp. I know it actually doesn't work that but it gives you an idea. Actually my guess would be higher than that estimation.

longrange4u

iTrader: (2)

Just my 2cents... These guys are right.. your putting too much thought into it. Dont worry about PSI... just get what you can without Detonation. My TA is being tuned right now by Josh and Steve at LMR... I have a PT88... Currently making ~12 PSI before we turn up the boost... and Josh estimates I am already well over the 700RWHP mark.. your ST80 flows better then my PT88...

98turbls1

iTrader: (17)

I was also thinking that he could use a little bigger turbo because it would be more efficient and also it's going to be a front mounted turbo.. With a butt turbo you could stand to use a little smaller turbo because of lag (from everything that I've read about rearmounts and my brief knowledge that I got when I worked on my buddy's car) I've always heard that it's better to run a bigger turbo easier than it would be to run a smaller turbo harder to get the same amount of boost... All things being equal I would think that his IAT's would be a little lower because not having to work so hard for the cfm's... Like I said that I'm no subject matter expert but just relaying some educated knowledge and reading that I've done...

ChrisUlrich

I would just step up the turbo to the SX78 or SX80. That will do the job for you.

And if you can make an efficient 25psi through a 408. Good god that's a ton of power. 25psi through a 408 is soooo much boost. S88 made 20psi on a 370ci and made 1000whp!! Better turbo yes... but that's still nutso.

Firechikn

iTrader: (15)

Uh yeah, +1 what they said. I made a little over 800 on 13.5 psi on my 408. 25 lb!!, watch out. I'd bet on easy 300 hp more.

Gordon0652

iTrader: (4)

What turbo were you using?

Josh@KY-Turbo

iTrader: (120)

A 408ci LS1 and S91 will easily go over the 1000rwhp mark. I am getting ready to start another 6.0L manifold build using a S91 and BMR's New Turbo K-Member that will be going on a stout 408ci Engine.

Gordon0652

iTrader: (4)

What do you think about the ST80 and a 408? My plan is 850-900rwhp what if i change and think about a goal of 1000rwhp?

Jimmy P

iTrader: (177)

I think you will need a bigger turbo to achieve that 850-900rwhp with the TH400. It could be done with a M6..but I dont believe with that TH400, especially not on pump gas. I believe PSJ has a GT 47-88, TH400 setup, real good heads, BS3, etc, and is doing around 870?rwhp after the TH400. (on race gas)

Zombie

iTrader: (2)

Why aim for a "HP" rating on a dyno, it's not worth the paper it's printed on if you are dynoing a th400. The type of dyno matters too. Why not aim for a ET/MPH at the track since that will tell you what you are really making.

If your raceweight is 3800lbs and you trap 135 mph you are making 800 rwhp.

98turbls1

iTrader: (17)

Amen!!!
dyno numbers mean squat in real racing..

NA$TY-TA

iTrader: (21)

Heres my input.
I've made over 1100rwhp with 370ci motor.
That was at 25 psi and there is no way I would try that on pump and meth.
I was pushing quite a bit of water like that and finally blew a gasket running 118 octane fuel.
Right around 1000rwhp w/ 370 cubes and a S88 @20 psi
The above was thru. Powerglide and S60 rearend.
Be sure your fuel system is up to the task.

Kyle

Pro Stock John

iTrader: (34)

Me = 867rwhp (8:1 348ci, 25psi, race gas, no meth, truck mani's)

If I did a 408ci and tried to max it out on 93 and meth (which I would not do personally) I would run 8.5:1 compression and figure on 14-17psi to hit your goals.

I'm not much into dyno numbers, except that I went 9.4 with 680rwhp with the blower, and I went 9.4 with lower boost than my 867rwhp numbers, I just want to start running some 8's when it gets nice again.

Get a good converter too.

Gordon0652

iTrader: (4)

I am looking to do very high 8s to mid 9s at full weight. I know thats going to be hard to hit with all that weight and the TH400. Maybe my goal is too high, but i want to make this a plan!

Websy21

iTrader: (34)

Wow, 8's, shooting for the stars, just kidding but not easy task especially at full race weight. I think you'll need bare minimum of a S91 for show to get deep into 9's