brain

Couldn't it just be "better"? The new cobra has an iron block and it has 6 bolt mains. I wonder why all these stroker motor guys go to 4 bolt splayed mains.

HM Murdock

Don't assume all LS1's make awesome HP from the get go, and don't assume all LT1's take major head work to get over 400RWHP. I have seen examples of both. Of course it is harder for an LT1 to get to 400RWHP. We start at a 20 to 30 rated HP deficit.
It all depends on the car.

I have seen most pre 2000 LS1's(A4,s mostly) dyno in the 280's...The only exception I can think of is a certain red 98...Oh, that was mine.

I have seen many A4 LT1's dyno bone stock at 270.

It also depends on what mods you do.

Of course headers will give you more HP on a car that flows more air. Duh, that's called physics.

The biggest problem LT1's have is that the intake system(not just the manifold) is restrictive. 48mm TB??? 90 degree bend???That's a POS. First mod any good modded LT1 should do is a 52 or 58mm TB(for internally modded only), but I almost never see that happen. All these people complain about no power with XXX dollars spent, but they forget one thing, airflow. You can have the best cam, best heads, best longtubes, and make diddly squat if you don't free up the airflow on both ends, intake and exhaust. Remember, LS1's can barly take any porting to the TB, from 80mm monoblade to around 84-85. And you can't port the stock manifold, it's plastic.

Power is a direct product of airflow through the engine. The more air that can be pumped, the more power the engine will make. Plain and simple.

I say do 1.6RR's, 52mmTB, some LT's, an AFPR, and some better injectors and you are at at least a stock LS1, if not higher. Then start on Cam, heads, etc. and see the difference.

Remember, the LS1's only major advantage is one thing: Airflow.

Negate that difference, follow my advice and you are out maybe 1000 + install.

400 for Hooker headers, 300 for TB, 200 for 1.6RR's, 100 for used SVO injectors, 60 for APHR, and you have a 300RWHP LT1 with no internal mods.

Then add a good cam, high flow heads, etc.

Now look at TQ, though...You will see most LT1's torque numbers are stellar. LS1's have one disticnt advantage, they can rev higher, and flow more air at higher RPM's. More air= More power, that is a simple fact of life. Ge tmore air and more fuel into LT1's at higher revs, and they will make higher HP numbers. It isn't that LS1's are so powerful, they aren't. HP is nonexistant. It is not a measure of power. Torque is a measure of power. HP is a function of how much torque at what RPM. That's all. LT1's tend to fall on their face at 4500RPM's. Look at any stock LT1's dyno sheet, and you will see it. Add more air and fuel at high rpms, the car makes more torque at those speeds, and HP skyrockets. Do what I have said above, and you will notice a much better engine at high rpms.


You have to negate the LS1's inherent major advantage, airflow. Once you have done that, you will see making power is easier.

Fast Caddie

That's where it bites you. Air is a fluid and has mass like anything else, which means it has inertia(resistence to change in state) and momentum(the tendency to keep doing what it's doing). Assuming we're talking about NA engines only: Simply put, the LS1's 15* valve angle allows for a VERY tall port that gives a near straightshot to the intake valve, which means less restriction for the air. The more you try to manipulate air in laminar flow the more of its energy you waste in the process. Bernoulli's equation shows this by relating the pressure, kinetic, and potential energies of fluids. Since the air/fuel mixture can retain more of its kinetic energy as it travels through the port, it will move faster, keeping its momentum, and will go crashing by the valve and into the cylinder at a higher rate than the LT1 heads can provide. The LS1 head has better cylinder filling capability, hands down. LT1 heads "fall on their face" at higher rpms b/c they are reaching the point where they cause the intake charge to loose much of its energy; which is due to the bending and twisting the air has to go through before reaching the valve. Better filling= more power and more of it at higher rpms.

If you plan to match or beat one in the big end(all mods equal between the two engines) with an LT1, you better get ahold of some better heads. Which is why the suggestion of using the more radical genI heads came about earlier (like the 15*, 18*, SB2s). They have ports that approach the valve at a higher angle, and so they will produce more power. Physics is why the engineers designed the LS1 head the way it is. They used what the racing world has known for a long time and put it into a production head.

Now if we're talking forced induction engines, then that's another story. Inertial effects in a FI engine are not as important as they are in an NA since the blower gives the incoming charge a good kick of energy. All you need is fuel, something to cool the intake charge, and to boost that sucker to the moon and hope it holds together.

HM Murdock

That's exactly my point, the LS1 stock outflows the hell out of the LT1 and LT4, from air filter to tail pipe. it takes money to mod an LT1 to get the same amount of air into it. More air and fuel in a controlled ratio means more power. I am not just talking valve angle, but volumetric efficency. The LS1 can flow a larger volume of air, stock for stock, than an LT series engine. With mods, the LT1 can be brought up much higher in volumetric efficency. Just by nature of the 90 degree bend, the airflow is disrupted, decaying volumetric efficiency than stock. The ideal airpath is either forced induction, or ram air straight into the Throttle Body like the Ultra-Z or WS-6/Firehawk setup. Those are the ideal LT1/4 F-body intakes, hands down. With those intakes, volumetric efficiency is drastically improved over the stock Z28/Formula/Trans Am setup, due also to the velocity of the air entering the system.

What I was basically trying to tell him was that with basic mods, we can have the same power a stock LS1, but I never said the heads would flow more through the valves, stock for stock. What we need to do is get more air in the engine to compensate. I never said with equal mods. I was saying for the price of a stock LS1, you can have a modded LT1...