Hello everyone, I have a 1999 Trans Am with 95K miles that I bought out of an estate so I was fairly certain that some 18 year old and whipped the car to within an inch of its life. It had sat for about 3 years. The older gentleman who owned it had died several years before the sale and needed all kinds of deferred maintenance done to it.

So, I have replaced the entire suspension with a full UMI adj. setup except the engine cradle. Rebuilt rearend with all the goodies (new posi, Moser axles), all new upgraded brakes (Brembo 4-piston up front), all new fuel and brake lines, new Transzilla 6-speed with the Tick LS7 clutch package, and it came with a Borla cat-back exhaust system on it. Also upgraded the side marker and all front lights to LED's.

Now that all the other "stuff" is done on the car, I want to start turning my attention to the engine. It was tuned by someone and had numbers of 349hp/357tq on a Mustang dyno and 87 octane pump gas.

I want to start doing some things to the engine. I was thinking of starting with an intake manifold and came across a ported, by Vengence Racing, MSD unit with 42lb injectors and rails. Then perhaps get headers on it.

Am I wasting my time with this without doing heads and a cam? I was hoping for another 25hp with the intake. I'm pretty sure if I did go heads and cam I could add closer to 100hp.

 

To take best advantage of an MSD intake, you would need at least a good cam and then good heads. It won't really help a stock engine. A FAST would be better then.

 

Yeah, my other option(s) was a factory LS6 intake and injectors or maybe finding a FAST 92mm intake and a matching throttle body for whatever intake I would get.

I just thought that for $800, the MSD w/injectors and fuel rails sounded like a good price.

 

The factory LS6 (or Dorman copy) is a great choice for a stock LS1 and a huge improvement over the LS1 intake.

 

My other thought is to just pull the LS1 and put in an L92 with a Summit Pro LS Stage 4 cam. Richard Holdener has done this very test on a bone yard engine and made 568hp with just the cam swap. So $2K for a core engine, another $2K for a basic rebuild, $2K for the cam/lifters and LS3 intake and another $2K for misc. and for similar money I can have an additional 100hp vs $6-7K for upping the LS1 and ending up with less power.

A lot to chew on.

 

If you get a core L92 with under 200k miles, don't even go into the short block.
Refresh the valvetrain with fresh lifters, lifter trays, timing chain, and new cam retainer plate.
And a new oil pump.
Plus the new cam of course....

 

You will not be able to control the l92 with your factory computer without at minimum getting a converter box for the crank reluctor. Either way you will have to add tuning to your price estimates no matter what you do.

 

Right. That's where I have $2K for misc.

 

OP,

That's a nice 4th gen you have resurrected. It sounds like you've already done plenty to make it road-worthy and take it corner carving. Now you're in the never-ending hunt for more power. You're right you have a lot to chew on.

If you’re deciding between upgrading the LS1 in your '99 4th-gen F-body or swapping in an L92, here’s a quick breakdown:

Upgrading the LS1
Pros:
- More affordable: Bolt-ons like cam, intake, heads, headers, and tuning can give solid gains.
- Easier process: The engine is already in the car so a lot less time-consuming.

Cons:
- Limited power potential: The LS1's smaller displacement (5.7L) and older tech limit power compared to newer larger displacement LS engines.
- Requires pushing limits: To achieve big power, you'll need to push the LS1 harder, which could impact reliability.



Swapping in an L92
Pros:
- Bigger power gains: With 6.2L displacement and high-flow heads, the L92 easily makes more power.
- Modern tech: The L92 offers a better foundation of stock components for performance potential and efficiency.

Cons:
- More complex and costly: Swapping requires modifications to wiring, and tuning implications with the conflicting sensors and reluctor. This makes it a more expensive and time-consuming process.
- Fitment challenges: It sounds like you already know the L92 Intake and accessories might need adjustment for clearance in the 4th-gen.

Bottom line:
- Upgrade the LS1 if you want a simpler, more affordable build.
- Swap to the L92 if you’re chasing bigger power with modern technology, and don’t mind the added complexity.

Let us know if you need any further details or advice!

 

OP- Are you looking for big power or a nice increased nudge in the back when you push it?
Summit breaks it down nicely to help you decide.
It won't take too much to give your LS1 a bit more edge.
If your state doesn't do smog inspection, your options are wider than otherwise.
Long tubes will definitely help it, plus an LS6 intake.
A bit more cam would do even more, taking advantage of the increased breathing headers and better intake will allow.

 

well, where I live we do have emissions testing. BUT, since the car is now 25 years old, I no longer have to do that.

I don't think I need more power. I just can't leave well enough alone..........ever. I'm thinking I may put an LS6 intake on it and the long tube headers. I think I can get that done for about $1K. Then run it back up to B3R to retune it for around $500. I may also put a baffled oil pan on it as I've read that oil starvation and rod knock is a common problem without a baffled oil pan to keep oil flowing if you do much autocrossing.

 

I think that between the headers and LS6 intake, THEN tuning that combo, you will be pleasantly surprised at how responsive a combo that can be.
All those combined will be a solid upgrade to your car's performance, and with the upgraded suspension, will give you a car with a VERY high fun factor.

 

I didn't realize who this was that responded. Does Summit sell an LS2 intake? I have been reading that with a 90mm throttle body opening, I could achieve even slightly higher gains. And since I was going to get a new TB anyway and delte the EGR on the car since I don't have to e-check anymore, it just seeems to make sense to go that route. And seeing as even stock LS2 injectors are 34lbs. vs my car's 27lbs, that would be a sufficient bump in the capabilities. I've already upgraded the whole fuel system with new Racetronix pump and power wire and braided fuel lines all the way.

 

You do NOT want the LS2 intake unless it's the Dorman copy, which is actually much better than the OEM.unit.

 

Oooh, good to know.

 

OP,

You're on the right track considering upgrading the intake, especially with your fuel system already upgraded and the EGR delete in the plans.

To address your first question: As @G Atsma mentioned, the Dorman LS2 is a solid choice and outperforms the factory LS1 and LS2 intakes due to its improved airflow characteristics. However, with the current pricing being nearly the same as the FAST LSXR 102mm intake, you might want to consider the FAST unit, especially since you're already considering upgrading the throttle body. The FAST LSXR 102mm intake will boost airflow, making it a perfect match for the fuel system upgrades you've already done. Then add in the planned larger throttle body, long tubes, and a re-tune and it'll pick up some nice gains!

Regarding injectors, you're right about the stock LS2 injectors being 34lbs/hr, and that should offer you more headroom compared to your current 27lbs injectors, especially with the fuel system improvements. This, combined with the intake, throttle body, and long tubes, would give you the potential for noticeable gains in both horsepower and throttle response.

Then we're talking heads and cam. The chasing horsepower rabbit hole

Let us know if you need further help to choose between the Dorman LS2 and FAST LSXR or recommendations on throttle bodies and injectors. We're happy to assist!