Third gen i have a problem I cant seem to make up my mind which direction that i should go with the performance upgrade with my motor.I have a 91 gta that has a stock 350(l98) in the bay right now.I have recently puts some new parts on the engine like rebuilt stock heads,new water pump,and full 1.6 r arm,and headers.

I want a lq4 or lq9 and convert over to lsx.The reason why the choice is hard because i have some good performance parts right now for my L98 to address all the short falls of the l98 like a elderbrock pro flo xt efi intake.ported ls1 tb,accel thrust dfi ecu and efi harness,32Lb venom injectors,the only things that i am missing are the aluminum heads and performance cam.

this where it gets hard,I can get a lq9 or lq4 for the for a the cost of the aluminum heads and the performance cam.but I know that the gen 3 motor are awesome hands down and make stupid power and get over 20 mpg for gas.I have to also look at the price for the conversion but I know it would be worth it if i go lsx.It would also be good if i rebuild what i have and thrown in the performance heads and cam since i have everthing esle including a full performance exhaust system.

I dont know which way to go.

 

Forget about L98 vs. LSx and decide what your performance goals are, and what your budget is. Only then can you decide how best to achieve those goals. If you're going to keep things fairly mild, the L98 is going to be the best option, but if you're going to go beyond a certain point, and still want good driveability, then the LS platform will prevail.

With either platform, you again need to be sure of what your performance goals are, and build your motor around those goals. Right now your parts selection for the L98 seem to be a bit scattered. That Edelbrock intake is designed for high rpm use on larger cubic inch motors with big heads and a big cam. It's not an appropriate intake for use on a mild 350. Your "only thing that you're missing" (heads and cam) are the two most important choices that you need to make, and again, they need to be chosen to fit your goals. I'm not sure why you'd want to spend money on a stand-alone DFI system when the stock computer & harness are perfectly adequate for all but the most extreme setups.

What do you want your car to do? Let's start there.

 

well thats the thing i dont have to spend the money on a stand alone dfi system because i already have it.all parts thats listed i already have the only thing that i would need to purchase would be the heads and cam.I just dont know if i should go the lsx route or the use that parts that i have rebuild the short block and match the head and cams together to work.

 

[/quote] What do you want your car to do? Let's start there.[/quote]

I want the car to have power be drivable and get ok mpg.I know i cant really compare the two but kinda of like a lsx platform.they make can easly make 400 and get over 22mpg.but its the cost of the conversion that can get pricey fast

 

"have power and be drivable" pretty much describes every car on the road. It's how much power and how drivable that determines what you should do.

But let's assume that you're looking for a nice, low 13 or high 12 second car that can still get 20+mpg. To me that's a powerful car for the average Joe.

To get there, you can take a couple paths. First is to mod your L98. A decent set of Trick Flow heads ($1200), a decent roller cam ($300), headers & y-pipe ($0 if yours are a decent set of 1 5/8" headers), 3" catback ($250) and either TPI intake mods (ported base, SLP runners, ported plenum, total of about $300 if you can port them yourself), or something like a Stealth Ram ($750). Throw in a couple hundred more for miscellaneous items including gaskets, and you're at around $2250-2500. There's plenty of opportunity to save money here by having your current heads ported instead of buying new heads. Swapping out your harness and ECU for your DFI may or may not be worth it. Unless you're proficient in tuning the DFI and you're not able to tune the stock ECU, it seems like a lot of work for nothing, even if you already have it.

Option 2 is to go with an LQ4. The motor will be around $750-1000, headers $500, $500 for a set of f-body accessories, $250 for an f-body oil pan, and if you don't want to stick with the goofy truck intake, you'll need another $500 for an LS6 intake and cable throttle body. Figure another $100 for the motor mounts, and another couple hundred for misc installation stuff. Unfortunately, now you need to deal with the transmission, because your 700R4 won't just bolt up. You can buy an aftermarket flexplate, and some sort of adapter for the TV cable. You'll also need to build/modify (or pay for) a wiring harness that will work for your configuration in your car, plus an ECU. Figure around $400-500 for that stuff, excluding the custom tune, which will be another few hundred. Lastly, there's no way I'd put an LS into a car without a cam swap, so plan on another $400 for the cam, and $250 for new valve springs. The LS is also notorious for puking needle bearings out of the rockers, so another $100 for the Comp trunion kit. This option is at about $3300 so far, and I'm sure I'm missing plenty of little things that will add up. If you're thrifty you might be able to pull of this swap for $3k. Depending on your cam choice, this option should give you more power than the first option, but will be considerably more work.

Which would I do? Well, technically I'm doing both. But, if I was just doing one car, I'd stick with the SBC. It's cheaper, and much faster, which means that you'll be on the road enjoying it sooner. I don't really think that the LS becomes an attractive option until you start getting into higher power levels where you're forced to upgrade the rest of the drivetrain anyway. In that case, the motor accounts for a smaller percentage of your overall expenses, plus with higher horsepower levels, the LS can keep it's table manners, which will make for a much more pleasant driving experience. But, at more modest horsepower levels, the SBC will offer good drivability.

 

I'd stick with the L98, LSx engines are great and have their benifits but financially and just the amount of work put into an LSx is a lot. Sounds like you already have some parts together so why not stay on that path? I personally would stick with the L98 unless theres a crazy high amount of miles on it.

 

the motor has like 137 original miles on it

 

I like my L98. With that little wear on the engine...L98 for sure!

 

I would use whatever parts you have to give that L98 a little kick, and when it sees the end of its life (not sure how long that'll be with that many miles), then go the lsx route. You'll get expirience with both and will probably be the easiest route to go.