ohsixgt1217

Im sureyou did. FI needs that little bit more to breath. I havnt talked to anyone besides you that has shorties on a fi car, the only thing i saw was shorties on a N/A car, and without FI the car wasnt pushing enough air to make a difference between the shorties and the stock manifolds.

Dennis074.0

on the smaller CI engines (like the 4.0 for example) shorties are good, I'm not sure if they are too good with the 4.6's being so the stock headers were built rather well by ford.

I do know that the shorties will give more of a growl on any engine though.

GT Bob

I have long been in the Anti-shortie camp, and have often spoke out against them... but my opinion is starting to change. A buddy of mine's uncle designs and builds custom 6 into 1 headers for BMW race cars and has been consulted by BMW and other car makers about design of headers and manifolds, so he knows something of the subject. I mentioned getting headers to him for my stang and he offered to help me pick some good ones out.

We took atrip to the speed shop near him, took some measurements of the headers and my manifolds,and after doing some math, he is of the opinion that you will not gain anything PEAK from the headers. As someone already said, the 4.6 won't push enough air without FI to out flow what the stock manifold will handle. However, he thinks that off-peak gains would be pretty good...the highest gains he felt that I would see are somewhere above 10HP and Ft/lb but probably not more than 15, through improved scavenging of cylinder gasses after the combustion event. He started talking about pulse modulation or something like that and lost me at that point so I can't really explain it any further than how I have.

One this alone, I wouldn't have changed my opinion, because I have seen too many times where math was proven wrong in the real world. However, I also read an article in 5.0 mustang mag about Miller motorsports park. They run only Mustang GT'sthere, and with nothing butoff the shelf FRPP parts. The only "go fast" parts they use are the intake, Shorties and mufflers, they are getting 335 crank HP and 345 Crank Torque... and since the FRPP intake/tune is only getting 19 HP... there's 16 coming from somewhere...

Now, I'm not saying they aren't just adding up the "claimed"numbers that FRPP puts on their parts... but both of those things have me thinking enough that I am going to take a chance and get a set of Shorties. I could really care less about dyno numbers... ET's and trap speeds interest me more and something that can improve either one for not a huge Dollar amount is something I will try. Worst case, I'll chalk it up as a learning experience for the Mustang community, and have my stang growl a bit better when I jump on it.

SCCAGT

My .02 I bought BOTH BBK and FRPP shorty headers. Visually looking at them, the FRPP headers were not up to the same level of build quality as the BBK. They really didnt look mush different than the stock logs. The BBK's had a thicker flange. Also, where the tubes went into the flange, the shape was flat on the bottom instead of round. I put on the BBK's.

Installation of the FRPPwould bemuch easier. They are smaller and do not require lifting the engine off the mounts to install. No matter what header is used the steering shaft needs to be disconnected and moved out of the way, and the starter needs to be removed. I dont see how the shaft would clash with either header as someone else stated. They hook up to the cat pipes exactly like the factory logs.

As far as sound, the BBK's header SEEMS to have made mine slightly quieter. The exhaustpulse coming out the back is also a little different. I say if the shorties made a difference, power wise. My butt meter cant tell the difference between 500 and 510hp. My car has been dynoed twice. Once with just Procharger (everything else stock), then again with exhaust and headers. Both runs on ProChargers Mustang dyno. The difference was only 10hp between them but the temperature was about35-40 degrees warmer on the second run.

Sleeper05

intake, 4.10s, shorties, no cats, flowmaster mufflers, pulleys, and a dyno tune at JBA.