Currently I have a LB9 that is burning and leaking oil like theres no tomorrow. So I picked up a L98 Long block out of the same year IROC as mine. I could just throw it as is with bigger injectors and a new prom, but who wants a stock motor?

So what would it take to get 400 Hp and 450 lb.ft. N/A?

Would building the 305 or 350 iron heads, porting the stock intake, bigger TB, cam and injectors make it? Or would I have to build the bottom end also?

 

A 383 will give you an easy 400/450 at a street usable rpm range, doubt you can get 400/450 out of a 350, seems at the 400/400 level torq starts to drop off as the hp increases.

 

whoops....

 

I think you will run into soem tuneing issues with that . Also 450 hp seems to be the breaknig point for the stock L-98's bottom end ( according to online sources like here ) . So I think a new set of rods and a crank ( forged ) are in order. Are you trying to keep it TPI ? What are you worried about as far as emmissions?

 

No emmissions here, so don't have to worry about that. I would like to keep the TPI because it seems more streetable and well, already have it so it would kinda be cheaper to upgrade than to carb or something.

 

that nine point somethin' compression would love some boost.....
but a 383 is a fast way to what you want but not a garrantee if you skeeve on the intake choices
its hard to run like hell when yer breathin through a straw

 

The stock runners are just aluminum tubing so they cant really be ported so I think the Edelbrock or SLP runners will make the list.

What about the stock manifold? Can it be made to flow as much as the aftermarket ones?

 

I have a 91 gta with the L98 350. The previous owner dynoed it right before i purchased the car and ran 191.2 to the wheels. So if i did the following mods on it how much do you recon i would put to the ground

Holley Stealth Ram
BBK 58mm Throttle Body
383 stroker kit

What is your take on porting the stock heads for now?

 

A SD L98 should put down 220 or so to the wheels.

As for that setup, your lucky to get 250. Get rid of that TB and 382 and get some aluminum heads, Sealthram and a big *** cam.

 

You sure it's a 350? My 305 dynoed 187 to the wheels. Does the car run ok?

 

Its a 350 alright. Before i bought the car, my buddy replaced it with a rebuilt. Also i have a th350 with stall converter, that was also installed before purchase. I know you lose around 15-20% of power at the crank.

So far i added hedman hedders with 3 1/2" mufflex exhaust system. I plan to do the HSR and TB when i get home. I already got my superduty hood for the clearance for the intake. If i have some extra money left over im going to go ahead and purchase the stroker kit.

Im going for Naturally Asspirated. Hope to be making around 350 to the wheels, maybe more.

 

To the original poster, 400rwhp definately aftermarket heads and cam. Dont think you can make 400rwhp N/A with the stock heads, even with porting. TPI generally makes alot more torque than hp, with the right cam and heads it can be a torque monster. But not a horsepower monster. That dosnt mean its slow though, just a different powerband. Maybe consider a power adder like nitrous.

To Pearl91, I think 350rwhp is possible but its a pretty high goal for L98 heads and N/A. Like way up there. Definately need a short runner intake, aftermarket high rpm hp cam, alot of head work, and most importantly a good tune. 350rwhp is my goal for the 350 I'm currently building for my IROC-Z, expecting to spin it to 6500rpm all day (kind of abusive but track only).

 

The car that Pearl91 is referring to is my old car. I did blow the original motor in the car about 3 weeks after I bought it. Replaced that with a rebuilt motor from a local rebuilder and thought that what I had was an L98 motor. I am not sure as to what the block actually is, the heads that are on it are the TBI swirl ports...I do know however that it is a 350. That is the main reason that the car is only making the power that it is. I was really amazed when I did that last dyno on the car and it put down 191rwhp/350rwtq.

Just figured I would add a little pertinent info to this so that everyone knows the deal on the car.

 

Thanks white!!!

 

Ok heres a rough idea of what im thinking. Help me fill in the details.

Scoggin-Dickey intake, Vortec heads, SLP runners, BBK TB, cam, injectors, bored .030 over and forged bottom-end.

 

It's always nice to have the biggest badest stuff . But forged rods and crank may be overkill for that STREET setup. Unless ofcourse you have other plans for the car where the extra strength may be needed ( N2O)

 

Well, the car will be tracked some. Its not my daily driver by any means. I want to get a good amount of power out of it and know its going to be reliable before I jug it.

 

Anymore ideas?