How do I make 360 Rwhp

bigbird04

Active Member
Jul 15, 2010
106
7
38
Decatur Al.
Last car was a 99 Z28, full bolt ons netted me 356 Rwhp and 362 fLbs. How do I make similar power out of a 2V 04 GT. Nitrous is not out of the question, (although I'd like to make some of it with bolt ons) I know these cars don't respond to exhaust and cold air kits like ls1s do . I know they like boost and nitrous though. How much juice is a stock 2V up to, dry/wet ? F bodie guys love harris speed works anyone runnining their plate kit on a 4.6 ? Its going to be a fun street car not a dd though.
 
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Firstly, your GT is about 200 lbs lighter than your Z, so the same performance can be had for less power. However, long tubes and an H-pipe will get you a good 20-30 rwhp, and some serious cams and heads on top of that would get you the rest of the way to your goal... but really, slapping a Kenne Bell on top would get you there in one fell swoop. Also, these cars respond very well to gears.
 
It's hard to compare a 5.7L LS1 to an engine down more than a liter in displacement, especially the 2V modular. Let's face it: The 281 cubic inch 2V mod with its 3.55" bore is never going to be the power or torque monster that the LS1 can be in normally aspirated form. Even the newest 5L "Coyote" 4V "only" puts down ~360 to the wheels and it's claimed to have the best flowing heads this side of F1. A stock blown Terminator Cobra 4V puts down similar numbers.

As slayer said, you can bolt on aftermarket heads (the only ones available for the 4.6) from Trickflow, get some aggressive cams and an exhaust and I'll add a short-runner Reichard racing intake manifold and you might approach that HP number but it'll be at fairly high RPM.

You need to make up for the lack of cubes with artificial respiration, IMO, if you're looking for the kick in the ass that an LS1 will give. This means a blower or nitrous. A stock 5-speed 2V PI motor will make ~230HP at the wheels. The stock bottom end is safe up to the 400-425rwHP range on a safe tune so you could, in theory, bolt on a 125-shot and get what you want with a reasonable margin of safety.
 
I have the Harris Speed Works plate kit on my GT. I like it a lot, fitment was great.

Currently a 100 shot, but I'm tempted to move it up. If the engine is in good shape, a 125 shot shouldn't be an issue. Just make sure to back down a couple degrees of timing. It'd be a good idea to upgrade the fuel pump (an SVT Focus fuel pump is not too expensive and a great upgrade) just to be sure. And of course, it's also a good idea to have the air/fuel ratio verified via dyno or wideband.
 
Jim your set up sounds like its making great power. I wouldn't imagined a 4.6 (N/A) making 355 none the less an auto. If you don't mind me asking roughly how much did the heads, cams, gaskets,ect cost, just parts not labor. I'm basically a mechanic for a living. I feel confident doing the wrench turning myself ( plus a few friends and beers give or take ) I'd leave the tuning to an expert though.

Burningrubber judging by your times sounds like you are right where I want to be also. I have a few questions though.

Are 410s to much gear for your car, is first even usefull with spray ?
Do you have harris's controller, if so how do you like it ?
If you don't mind how much did your set up cost ? I think I probably do a good kit for 1000-1500 dollars
 
Not really, power is power. If the internals can withstand 450 Hp, and you build a combination that makes 500 Hp with those internals, it's going to blow up just the same whether you used FI or an N/A build to do it.

High power on small-displacement engines like the 4.6 generally means lots of RPM. I'd rather use higher cylinder pressures and a safe tune than a ton of RPM and a leaner tune to achieve the same power, especially on a 2V variant that has the disadvantage compared to the 4V motor of larger, heavier valves to control.

Plus the added bonus of that cylinder pressure is torque (at least for positive displacement blowers) down low, something a stock 4.6 is lacking and which is only made worse when the powerband is moved up in the RPM band on a 4.6 tuned for high power.
 
Jim your set up sounds like its making great power. I wouldn't imagined a 4.6 (N/A) making 355 none the less an auto. If you don't mind me asking roughly how much did the heads, cams, gaskets,ect cost, just parts not labor. I'm basically a mechanic for a living. I feel confident doing the wrench turning myself ( plus a few friends and beers give or take ) I'd leave the tuning to an expert though.

Burningrubber judging by your times sounds like you are right where I want to be also. I have a few questions though.

Are 410s to much gear for your car, is first even usefull with spray ?
Do you have harris's controller, if so how do you like it ?
If you don't mind how much did your set up cost ? I think I probably do a good kit for 1000-1500 dollars

Just check out my online store. I have TF heads on sale for $1950 and my cams are on sale for $559. Also have head/cam combo packages as well to save a couple more bucks.
 
Not really, power is power. If the internals can withstand 450 Hp, and you build a combination that makes 500 Hp with those internals, it's going to blow up just the same whether you used FI or an N/A build to do it.

im gonna disagree there, the internals come apart at 400+hp on F/I engines because of added pressure from the added air/fuel. but a n/a engine with that same hp is because of the engines efficiancy to utilize the same fuel pressure as stock and un restricted air flow now, with the tf heads they use a smaller combustion chamber also, and larger intake valves for a less restrictive flow path. there is to a point added cylinder pressure but non as if there is from f/i. the heads bum compression to ~10.5:1-11:1 depending on grade of fuel used and higher with race fuel. with a s/c@9psi you compression jumps from a stock 9.5:1 to almost 12.5-13:1 ratio, thats why rods bend and break on stock bottom ends not from hp ratings at a given rpm. now i realize that there is a limit to these engines as far as rpm goes also. in conclusion when using FI you need more fuel for the added incoming air, but with n/a your utilizing and making the engine more efficiant to produce more hp. if it were me and my money id go n/a its safer, and i dont need more than 375hp on the street or a dd
 
im gonna disagree there, the internals come apart at 400+hp on F/I engines because of added pressure from the added air/fuel. but a n/a engine with that same hp is because of the engines efficiancy to utilize the same fuel pressure as stock and un restricted air flow now, with the tf heads they use a smaller combustion chamber also, and larger intake valves for a less restrictive flow path. there is to a point added cylinder pressure but non as if there is from f/i. the heads bum compression to ~10.5:1-11:1 depending on grade of fuel used and higher with race fuel. with a s/c@9psi you compression jumps from a stock 9.5:1 to almost 12.5-13:1 ratio, thats why rods bend and break on stock bottom ends not from hp ratings at a given rpm. now i realize that there is a limit to these engines as far as rpm goes also. in conclusion when using FI you need more fuel for the added incoming air, but with n/a your utilizing and making the engine more efficiant to produce more hp. if it were me and my money id go n/a its safer, and i dont need more than 375hp on the street or a dd

And 400+ Hp N/A engines come apart because of high RPM's. In the end it's generally a wash, and without significant data on the weaknesses of a specific engine, you can't make a call on what is safe"er" with reasonable certainty. If you stay a good safety of margin under the maximum hp rating on the internals, it shouldn't matter whether you use forced or natural aspiration.