03CHEVYBOY

iTrader: (1)

No not everyone except for me. If your a hater and thats your thing fine, this is the last reply directed towards you, i would appreciate positive attitudes and intelligent discussions, leave your ignorance elsewhere

EVILGMC

iTrader: (47)

bassani mid length.... or just stay stock. i had shorty jba ceramics....total waste of money.

MikeGyver

iTrader: (5)

The reason for having headers is not to increase exhaust flow by means of a better flowing exhaust, stock manifolds flow plenty of air. Headers increase flow by timing the sonic waves that are produced when the exhaust valve opens. When the wave exits the primary tube and enters the collector, it produces a negative wave behind it. This negative pressure then helps pull the exhaust gas out of the next cylinder, as long as it is there when the next cylinder's exhaust valve is just opening to get the effect. The timing of this wave is adjusted by the length of the primary tube. The longer the tube, the lower the rpm that the extraction effect is tuned for. The shorter the tube, the higher the rpm. You know that tuned length headers, or long tubes, are long. You also know that they work best in the 4000 and over rpm range. I seem to remember reading that the difference in street headers and race headers, for like 8000 rpm, is only a couple of inches. Therefore, the length of shorties, or even mid-length headers, must mean that they won't be helpful until 20,000 or some ridiculous rpm.
That gets back to airflow. Shorties probably flow more air than SBC log manifolds, for example, but not our truck (LS style) manifolds.
The only thing that shortys do better than stock manifolds is leak.
So my answer to the title of this thread is, "The best shortys for a 4.8 are the stock manifolds".

MikeGyver

iTrader: (5)

Then why do they make shortys, if they don't work? Originally, for hotrods where nothing else would fit. And just because they don't do anything besides look cool, doesn't mean people won't keep the myth alive. Think about the Tornado (Vornado?). They're still selling those.

silveradokidd_4518

iTrader: (14)

shortys are a waste of money. you can still run longtubes and still be smog legal too. just throw some cats on there you'll be able to pass

03CHEVYBOY

iTrader: (1)

Not here in ca. I think im just going to stick with the stock headers at least for now. I still have pacesetter long tubes for sale that i will not be putting on, brand new if anyone is interested.

MikeGyver

iTrader: (5)

I feel used. I usually can spot a "For Sale" thread, but you tricked me.

Chevy Cowboy

iTrader: (5)

Yes in CA, theres other users in here from California running long tubes and with cats that are passing the emission test, you just have to be willing to do a little bit of work or pay to get a y-pipe with cats that will work with long tubes, like everyone said, long tubes, or stock manifolds

viciousknid

iTrader: (8)

Long tubes are technically illegal for road use in every single state. That is why they are sold "For Offroad Use Only". This is because they move the factory Catalytic converter location. All you have to do is get a Y-Pipe made that has cats. This will allow you to pass smog in CA. Plenty of people do it.

As long as you Pass Emissions and are not increasing the loudness of your exhaust it is legal.
Your sig says you have an exhaust system. Did you check it to make sure you are less than 95db?

budhayes3

iTrader: (19)

I've heard that it's hit or miss in CA (as in some guys pass, but most don't), and they really bust ***** if the cats are moved from the factory location, even if they are still there. If I lived in CA, I would still get shorties just because I would want that extra 10 hp, and if you look at most shorties, the primaries are actually a tad longer than the stock manifolds. Since you're in CA where the weather is nice and snow and salt isn't an issue, you can get away with the less expensive steel shorties as opposed to stainless steel. I just sold my Gibson stainless shorties last week...I'll admit that I didn't feel any gains from them in my butt meter, but they were of quality construction, and they didn't leak.

What about mid-lengths, can you get away with them? You can still retain the factory cat location and the gains will be better than shorties...does Thorley still make mids? That would be my first choice over shorties if possible.

And for what it's worth...the shorties do look cooler than the factory manifolds lol