5.3 manifolds and stock y pipe on a lq9
 

hey guys, I am wanting to put my stock setup off my 5.3 onto the lq9 i will be swapping in soon. Will this significantly restrict my 6.0L. I really want to keep this motor torquey, and I defintely felt the loss of low end on the 1 3/4" dynatechs long tubes and y pipe when being on my 5.3. any suggestions??

cory

You'll be fine unless you plan on modding the shit out of it. I did this on a customers truck 8 years ago when we did a 5.3 to 6.0 swap and it runs great and never has had a cat failure.

no it just has mildly worked 317 heads, a isky 208/214 camshaft, and thats about it. Looking for a good smooth low end torque curve. not sure which of the two exhaust options will be better suited??

dynatechs and Y pipe

Your exhaust won't be significantly restricted, but I feel that the 6.0 would benefit from the bigger 1 3/4" primaries. The GENIII engines aren't really known for their low end performance, even stock, but I understand where you're coming from wanting to keep the low end that is already there. That mild cam will help keep the curve low FWIW though. Have you considered a higher stall torque converter to get the engine up into the meat of the powerband quicker? You could go for the mildest Circle-D upgraded trailblazer verter and still have a nice daily driver that doesn't require a ton of go pedal angle to get moving ;)

The loss of low end with headers is a silly myth.

From bone ass stock 4.8L exhaust on my H/C LQ9 to 1 7/8" 3" catless Y, the low end was exactly the same. Above 3-4k it comes alive with the upgraded exhaust.

The OP stated that he personally felt the loss of low end though, as have others. It all depends on the setup. Back in the day I had a bud with a sbc 79 Camaro, with 1 3/4 headers that was missing something down low (this was a street car, mild cam, intake, gears, etc.). He swapped off the 1 3/4 Hedmann's for some 1 5/8 BlackJack's and gained low end performance due to the increased exhaust scavenging. I later built my 71 Camaro for higher hp performance (bigger cam, intake, carb, converter, gears, etc. from the milder combo I had), and did the exact opposite swap in headers (I mean exact, from 1 5/8 BlackJacks to 1 3/4 Hedmanns), and they were a perfect match for my setup.

With more cubes, a bigger cam, better heads...basically more air in and out, bigger header primaries/collectors and exhaust tubing becomes essential, but a mild combo can survive without that if necessary. As I mentioned in my previous post though, I feel that the extra cubes of the LQ9 will benefit from the bigger primaries.

On another note though, when I swapped off my Gibson shorties in lieu of my current 1 3/4" StainlessWorks, I did not feel any loss in low end, but...my headers have small 2.5" primaries which may affect that, and at the time I was running 33" tires with 3.73 gears, so my low end was horrible as it was.

I dont see a problem with it.... gut the cats unless youre trying to keep it emissions legal for whatever reason. I've got a bone stock exhaust system on my truck with the exception of gutted cats and a dumped magnaflow and it runs just fine...

Headers on a 6.0 should not cause any loss of low end torque. If any thing, you will probably gain a little. The loss of low end you might have felt could have been in your head do to the loudness of the exhaust. The exhaust is a lot louder, so it feels like you should be going faster. I saw a header comparison on a 6.2 camaro where they tested different sized primaries. All the headers gained low end torque over stock.

5.3 exhaust will work fine, mine even pass cali's sniffer near or under the avgs across the board, though it is wise to upgrade to something better

i read an article in "Drive!" magazine, it tests shorties vs longtubes on a mustang 5.0 using BBK headers....the shorties made(over stock) 25hp/3ft lbs, the LT's made 41hp/2ftlbs with a new X pipe(catted).....the shorties did a lot for the curve, smoothing it out, on the graphs both set of headers had gains and loss' in the same areas, the stock manifolds were more like tri-y headers vs the equal length shorties which were 4-1, same with the LT's