Hi everyone. I picked up an L98 a few months ago, and I've stripped it down and cleaned it up. It's time for me to start thinking about what kind of mods I want to do to it before I swap it in place of my carb'd LG4.

Problem is, I don't really know where to start. I've been to a performance shop, and they directed me to some pretty generic sounding stuff that I'm not sure is what I really want. Does anyone have any advice on heads, cam, intake manifold? Carb? Not looking for a drag car, but I definitely want to see a big improvement over my choked-up LG4.

Information on modding an L98 is a lot harder to come by than the LTX/LSX is.

Thanks everyone!

 

Is the bottom end being rebuilt? If not, how many miles on it?

 

I just ticked over 80,000 miles. I'm replacing the 700r4 with a t56. Engine is being completely rebuilt.

 

I just did the standard headers & catback on my new L98. It's still not in the car, so I can't tell you much about it. But you could go with anything from cam swap to HSR or Stealth Ram to CAI to extreme power adder like turbo, procharger or nitrous. It's a new motor, so anything is possible. Just be prepared to do some prom tuning (or have it done) along the way. I don't know the first thing about programming chips, but that wouldn't stop me from modding if I want to. There's always somebody who can do your chip for you (for a fee).

If you're wanting to drop some money in heads and intake, I would go Vortec. But you have to do BOTH the heads and the matching intake manifold to make it work.

As far as the carb goes, you said you had an LG4, so why don't you just clean your quadrajet and pop it on there. That's actually as good if not better than just about anything on the market. But it's CC'd (which is a good thing if you feel like dealing with it).

Why aren't you just doing TPI if it's an L98?

 

The stock heads (if the original 083 castings) are pretty decent, no reason to change those if you just want to warm it up a little. If they are being rebuilt though, have the valve guides cut to handle more lift (in the .550 range should be good) and have them machined for screw-in studs and guideplates. Not totally necessary, but I highly recommend it. I've done that with all my heads, and it payed off the one time I broke a rocker stud because it just unscrews. Pressed in are a pain if they break, and can pull out by themselves with stiff valve springs.

First necessary mod is exhaust... put a good set of headers on there, either 1-5/8" or 1-3/4". Both are fine. Shorties are easier to work with, because they are easier to install and don't present the ground clearance issues that full length headers do. Hedman, Hooker, SLP all make good headers for these cars. I have the Hedman 1-5/8" shorties on my 350. After that, get the matching Y-pipe for the headers you buy and get a good 3" catback.

What cam you use depends really on what you want the car to do, and how good you are with ECM tuning (or if someone local can do that for you). GM's LT4 Hotcam is a popular choice for the L98 though - good power and torque, nice sound, but retains alot of good drivebility and decent gas mileage. GM sells a "Hotcam Kit" with the LT4 Hotcam, Crane roller rockers (1.6 ratio), pushrods, lifters, and valve springs/retainers, etc all for about $550 - its a really good deal, compared to buying it all separately, and they are good quality parts too. That cam is around .525" lift with the 1.6 rockers though, so you'd need to have the valve guides cut for sure if you used that cam (.495" or so with 1.5, so either way you'd have to have the valve guides cut with that cam).

Get pistons to get the compression ratio in the 10:1 range, and have the block "0 decked" when it gets machined as well. Thats just a combination of the right pistons (1.56" compression height like stock, not 1.54" like lots of rebuilder pistons) and the right machining on the block. A good machine shop should have no problem with this.

Thats what I would do if I were building an L98 anyway... just my $0.02

 

Here are my exhaust parts:

Hooker 2055s - the nicest thing is that they come with a y-pipe and all necessary hardware. And they have all the a.i.r. tubes and holes for 02 sensor. I am a big proponent of keeping my emissions down. I'm sure it only robs me of somewhere between 0-5 hp.

http://www.jegs.com/i/Hooker/520/2055/10002/-1

Hooker catback - http://www.jegs.com/i/Hooker/520/16823/10002/-1

Magnaflow hi-flow converter w/ 3" in & 3" out - http://www.jegs.com/i/Magnaflow/642/94309/10002/-1

This seemed like the "best fit" setup for my car ... and yours.

All of this was around $800.