zaksturbo

Im kinda new to mustangs, but i was curious to see what the 05 to 09 gt motors could hold on stock internals, i know that the older cobras were said to be able to hold 7-900 give or take, are the 05-09 gt's about the same? I wanna make somewhere in the 600's.

FastDEW

Forget 600 hp on stock block. Look for a built motor if you want more than 500.

Blacksmoke

03-04 Cobras were forged.

We aint.
I myself would'nt even go 500 without beefing up the internals.

dkersten

The crank itself can handle 550-600, but it gets tricky figuring out what you have at the crank.. I say at the crank, and not at the flywheel, because many things run off the crank that you won't see if measuring at the flywheel. If you run FI (a must to get over 380rwhp), the type of FI is very much the determining factor on how much power you can get out of the engine. Turbos have almost no parasitic loss, so the boost does a lot more.. you can run 8-9 psi of boost on a turbo and see 500 rwhp, which equates to about 575 HP at the flywheel. Perfectly safe on the stock motor assuming you have a solid tune. On the other hand, 8-9 psi on a roots style will get you about 425 rwhp, and a centri or twin screw will get about 440-450 rwhp at that boost level, and in every case the crank is seeing the same amount of power. The water pump, alternator, and even the weight of the pullies and belt all are parasitic losses that the crank sees but the flywheel doesn't.

Most people will just say that the stock 4.6 shortblock can handle 450rwhp, but that isn't entirely accurate. It all depends on the parasitic losses.. go with a turbo, an aluminum flywheel, and electric water pump, a one piece aluminum driveline, and light wheels and you will "safely" see close to 550 rwhp on the same boost level that most people are comfortable with when running stock drivetrain, heavy 18" or 20" wheels, and a belt driven blower. Of course, turbos have a LOT more torque (520-600 rwtq at 9psi), and the factory clutch will probably not even come close to cutting it.

FastDEW

The problem with the 4.6L is the rods. They won't make it, so your motor goes boom. I have seen stock motors blow when FI was used. I have seen two actually. Both suffered from the same exact failure. Connecting rods made holes in the sides of the block.

If you want 500+ HP, get a built motor, then FI away. Oh and find a new transmission and clutch too, you will need them.

Good luck.

forensicsteve

If you want 500+ HP, get a built motor, then FI away. Oh and find a new transmission and clutch too, you will need them.

Remember getting built this or that, will not guarantee that stuff will not blow up. I know quite a few that have lost built motors, including myself. Right now having a second 302 stroker being rebuilt/refreshed as a backup motor, anticipating the worst. Building up the car, for many, is the green light to really up the boost. I was at 22 lbs on last build and looking for 25-27 lbs on this build. Then you are right back on the jagged edge, except at least double the boost you were before...lol.

Then you have to pay attention to all the other major components like fuel, transmission, rearend etc. Everything has to be built up to support the increase in power, especially if the car goes to the dragstrip and races on a prepped surface. If you are going to race a lot, you will need 2 budgets.....1 for modding and another for replacing/fixing all the stuff that IS going to break.

One of the best mods I ever got was a trailer. It's been used by two of my mates that race their FI S197s as well. Both lost transmissions from racing.

FastDEW

For sure. Built doesn't mean industructable. But the rods on a stock motor will not hold to anywhere near the boost you are talking.

Anyway, you are right on. Excellent post.

Stkjock

like this question has not been asked and answered 1000+ times... please learn to use the search feature... you can learn a lot that way

dkersten

Yes, the rods are the weak point, and as evidenced by the literally ten+ thousand people out there with 2005-2009 3v 4.6's running FI, a safe tune and 10 or less psi of boost and don't "rod" the motor and you will be fine.

The only examples I have ever seen of a blown 4.6 3v (blown as in destroyed, not FI hehe) are either over 10 psi, over 6300rpm, or a tune that was too aggressive. In 2005, people learned exactly what the limit of this engine is, and adjusted tunes accordingly. Since then, the one's who blow their engines either do it at the track, or have a "dyno tune" instead of the one the supercharger manufacturer sent them, or were driving in a manner that was destined to break something.

Finally, I just want to add that while all the supporting mods are necessary once you go built and exceed about 550 rwhp and 500 rwtq, the factory stuff can handle below that with ease, assuming once again that you are not rodding the heck out of it. Many people go with a built (read forged) engine, go to 550-600 rwhp and the only change is the clutch. (fuel system is a given but most supercharger or turbo kits address this).

candymanjl

I'm at 480whp (dynojet) and have been for about 4,000-5,000 miles now on the stock Kenne Bell tune. so far so good another member on here has 550whp (dynojet) on his stock motor with my same kit just the addition of water/meth injection. he's been running that for 2 years now.

it all depends on the tune and how aggressive it is with the timing. too much timing and 400whp you'll go boom, conservative tune and 550whp could be ok.

that being said I'm sticking to a 500whp limit until I build the motor. and I'm going to run water/meth before I even go to 500whp just to hedge my bet when it comes to avoiding detonation.