No Power? slow as a dog!

[Doug_Scott]

Already did seafoam, and yes it pulls a lot harder after 4 grand. It sounds great, but I have shut for lower end torque. I used to be able to spin my 35s on dry pavement but now it won't even think about doing it on wet pavement.

 

What gears do you have? My 2010 4.8 came with 3.23 and could not spin a tire to save its life, put the 4:10 gears in, and got a tune, now I can not only spin, I get rubber on the 1-2 shift if I am at just the right amount of throttle.

 

Typically if you lower back pressure only, you will lose bottom end, but not top end. If you increase back pressure(talking minor change, not a large change) you will lose top end power, but not low end power. Anything beyond a muffler change needs to be thought out and planned for. You cannot just toss long tube headers on, and make a custom dual exhaust (actually that is redundant, you have no choice to install a custom exhaust in this case).

 

Manufacturers do not just stick parts on because they got them on sale. It is all engineered. Flowmaster have many different models of mufflers. You need to get the correct one for your engine setup.

 

Engines today are not like they were in the 60s and 70s. We are getting huge horsepower and torque numbers now compared to the 60s and 70s due to the engineering and design changes. Slapping any old muffler on can undo a lot of that engineering. In the 70s, Thrush mufflers were the choice for many, it was a cheap straight through, fibreglass wrapped core. They would last maybe 2 years before coming apart, then it was back to the speed shop, drop $40 on the counter and take two home. "Cherrybomb" mufflers cost twice as much, but did not rot out as fast as Thrush.

 

In the late 70s, turbo mufflers were the big deal. Those mufflers originated on the Corvair. Back then Ford was the only manufacturer to use a x-pipe on dual exhaust(actually it was an H pipe). All the rest used "true dual" exhaust. For some reason, bench racers thought the H pipe killed the advantage of dual exhaust. Running open headers on street car would just kill the bottom end, unless you did a fair amount of carb tuning. Didn't stop the kids from dropping the pipes at the collectors for the street races. Since everyone did it, the results were the same, everyone lost bottom end, so no one really noticed.

 

Point is (and yes I took the long way round to get here), don't just swap a muffler and expect anything but less bottom end power. Make the muffler part of the system, not the cornerstone.

[Silverado4x4]

 

What gears do you have? My 2010 4.8 came with 3.23 and could not spin a tire to save its life, put the 4:10 gears in, and got a tune, now I can not only spin, I get rubber on the 1-2 shift if I am at just the right amount of throttle.

 

Typically if you lower back pressure only, you will lose bottom end, but not top end. If you increase back pressure(talking minor change, not a large change) you will lose top end power, but not low end power. Anything beyond a muffler change needs to be thought out and planned for. You cannot just toss long tube headers on, and make a custom dual exhaust (actually that is redundant, you have no choice to install a custom exhaust in this case).

 

Manufacturers do not just stick parts on because they got them on sale. It is all engineered. Flowmaster have many different models of mufflers. You need to get the correct one for your engine setup.

 

Engines today are not like they were in the 60s and 70s. We are getting huge horsepower and torque numbers now compared to the 60s and 70s due to the engineering and design changes. Slapping any old muffler on can undo a lot of that engineering. In the 70s, Thrush mufflers were the choice for many, it was a cheap straight through, fibreglass wrapped core. They would last maybe 2 years before coming apart, then it was back to the speed shop, drop $40 on the counter and take two home. "Cherrybomb" mufflers cost twice as much, but did not rot out as fast as Thrush.

 

In the late 70s, turbo mufflers were the big deal. Those mufflers originated on the Corvair. Back then Ford was the only manufacturer to use a x-pipe on dual exhaust(actually it was an H pipe). All the rest used "true dual" exhaust. For some reason, bench racers thought the H pipe killed the advantage of dual exhaust. Running open headers on street car would just kill the bottom end, unless you did a fair amount of carb tuning. Didn't stop the kids from dropping the pipes at the collectors for the street races. Since everyone did it, the results were the same, everyone lost bottom end, so no one really noticed.

 

Point is (and yes I took the long way round to get here), don't just swap a muffler and expect anything but less bottom end power. Make the muffler part of the system, not the cornerstone.

 

A lot of truth to what you said Doug they also though more noise meant more power which is not true at all. The only motor that benefits from headers is a high HP motor that spends most of its time at high rpm plus running headers created more under hood heat sucked into the air cleaner and killing more HP.