I was talking to some car nuts the other day and they said I made a good choice of getting the shorty headers instead of L/T's and when I asked why they said L/T's only get their peak performance on a 4.6 with forced induction because the output is so small it's like blowing through a 3 inch diameter straw and could possibly damage performance...

 

Don't know for sure but it does make sense unless you have some wild mods on a 4.6.

 

if your going to get headers why get the shortys, might as well get the long tubes because you KNOW your going to mod your mustang in the future. At least thats me.

 

LTs will make bigger gains especially after other modifications are installed.

 

LTs will show rewards at any level of mod. The gains increase relative to the modifications made. Shorties show some gains, but if you go forced induction, they won't offer much more, where the LT will really shine. LTs will not hurt your performance really, but you'll need better flowing induction (CAI, TB/plenum, etc) to see any real gains form either one.

Good luck

 

how much do TB/plenums cost?

 

somewhere around 350-400 depending on brand and where you buy from.

yes, because long tubes will see better gains with a s/c than without. but that doesn't mean that they are worse than shorties. peak is the key word there. any mod is going to have a better performance with a s/c.

 

Ah yes, grasshoppa. Many folks here go with the bigger is better routine . There is a fine balance between not enough flow and too much on a NA engine. First, one must calculate the total CFM the engine is capable of producing at redline, that will give you an idea of your exhaust volume requirements. Even if you open up your intake my guess is you are only flowing an extra 200CFM max with a stock intake/plenum combo. What goes in, must come out, why do you need drainpipes to move an extra 200 cfm. Second, slight backpressure is needed for cylinder packing, or you will start to suck out your fuel/air charge as the exhaust valve is closing, thus reducing power and economy. In my opinion, shorties are fine, (many guys do phenominal with stock manifolds) get rid of your stock cats though, Hi flow cats or O/R H or X, you will see improvement, probably to the engine's capabilities. Even the stock cat-back is adequate, I saw a guy that posted videos of his 1/4 mile times (12.93, best), he used a stock cat back, 4.10's, O/R/X, drag radials, drag suspension, he had stock airbox/TB, he just took off the snorkel! So my opinion is LT's aren't neccessarily the answer in NA.

John

 

Every dyno chart I have ever seen shows that long tubes outperform shorties by 15-20 HP.Stock engines also show similar gains.
Shorties are no easier to install than long tubes or mid-lengths.
Backpressure is a hinderance to performance at all levels.What most people refer to as backpressure are actually reversion waves.
Every material has mass.This is true for exhaust gas as well.Exhaust gas that has mass also has inertia whether it's sitting still or shooting out the exhaust.The exhaust gas will continue to shoot out the exhaust untill it either hits something or gets to the end of the pipe.When it hits something whether it's a bend in the system or an O2 sensor it causes part of the flow to be sent back toward the cylinder.This is a reversion wave.They can be used to pull part of the unburned mixture out of the cylinder into the exhaust,making room for more fuel air mix.When the wave comes back toward the cylinder and the valve is still open,the fuel air mix that was in the header tube will be forced back into the cylinder,sort of supercharging the engine.This improves volumetric efficiency of the engine and has a marked effect on power.Anyone who has ridden a two stroke dirt bike has felt the extra performance of reversion wave tuning.

 

They were full of ****. LTs are worth 15~ RWHP on a N/A GT. Shorties are worth MAYBE 2-4 RWHP if that.

Alot of times you don't even see a gain with shorties on a N/A 4.6L