I have a 67 Camaro with a crate 350 motor. It is the 290hp delux crate motor. When I had the car, it had a mish-mash of 2.5", 2.25", and 2.0" exhaust and the factory exhaust manifold. It had Flowmaster 40 series mufflers and sounded pretty good. But I wanted to add headers.

I had the exhaust changed to full length headers and a Flowmaster 2.5" kit with the "H" pipe and super 44 mufflers. The exhaust looks great and sounds good at idle, but when you stomp on the gas the tone is trumpet-like and the motor sounds lazy.

I thought the timing was off, but it seems that the timing is good and the Holley 650 is properly adjusted. My buddy thinks the motor sounds lazy because it is flowing better now, and the next step is to add a top-end kit (cam and heads) to pick up the compression and HP.

I am torn if I should go that route or not. Should I restrict the exhaust back by adding a reducer from the 2.5" to 2.0 inch? Would that help with the tone? Or is my mechanic buddy right? I just hate to spend the $$$.

Maybe I should have kept the old exhaust.

Here is the video of the sound today...

 

sounds fine but you did not get on it to hear that sound you refur to I would live with it, no you lose hp bye going back to 2 inch most guys are going 3 inch pipes ,I have true duals 2.5in an love it on my 406,

 

You might have gained 25 hp by going with the headers and big exhaust, but you might have lost some torque. Especially in the lower rpm's.
Your friend is right, that in order to really take advantage of the exhaust, you need to push more air through your engine with a bigger cam, heads, intake and carb. But you need to give this a lot of thought. I think its a mistake to build an engine to match a big exhaust in order to make it sound better.

 

mine felt like 40 hp after takeing off the manfolds an putting on headers ,it was not breathing right ,felt to much heat from under car was shaking ,not now with some things fixed too head phones work so much better or good speakers,mine is going over to cherry bombs soon the echo is the garage its in.an I have changed a lot of things like where my fuel pump is in the back now an the one wire atl is gone for a better one the wolleing sound you hear is the headers letting the engine breath so much better as well,soon I am going to cherry bombs as I have broken spot weld in one of the single chambers,this was well over a year ago too,but you should stay with what you got

 

2 1/2 will work fine.I have that size on both my 1981 El Camino SS.(also a 290 HP engine ) and my 1979 Camaro Z-28 RS with a 500 HP plus Supercharged small block.Since you have freed up the exhaust you will probably have to re- tune the car.Have you checked the spark plugs they might be lean.

 

may want to try bigger carb. 290hp 350 in the gillnetter had a 780 dbl pumper on it stock.

 

A Holley 650 is plenty cfm for your engine, but you may want to fiddle with and increase your jet sizes. It's not a lack of cfm issue, you're likely running lean now. Yeah, craby's boat had a 750, but boat engines are designed to run flat out most of the time, acquiring balanced street performance isn't an issue on water.
Your exhaust pipes are not too big, but the more free-flowing exhaust with headers and bigger tubes moved your hp/torque curve to a higher rpm. This is where the "less exhaust back pressure made me lose power" myth originates.
I heard a (tire?) chirp as the trans shifted from 1-2 going trough the turn. If that's what I'm hearing, the trans is upshifting too soon. Are the vacuum modulator and detent cable connected, or are you running a non-stock setup?
From the sounds of it, you didn't have your right foot planted heavy to the floor? Speaking of planting, with the engine off, have a buddy put the gas pedal to the floor while you look down the carb to make sure the butterflies are straight up and down (wide open throttle). Also make sure your choke butterfly is opening all the way when hot. Start with the basics, and work on tuning the carb.

 

yes agree I have 650 on mine with 400+ hp an 450 tlbs concervative ,all we did was turn my carb down a bit if a carb is tuned right you never need to change plugs either same set from breakin I have running fine .750 or bigger would be for 600hp guys don't relize he could probley get way with 500 cfm fine mine was lean stinky so we turned it down ,now runs like a champ,he could have shift kit in like mine it does the same when I forget to shift chirps the tires,though that seemed to early to be shift kit same thing after headers may turn it down a bit ,most guys can do it by sound rmps in gear an out

 

Great sound depends on the person, someone else may think your old system sounded restrictive, but I think I know what you mean. My 325 hp 67 still has a 2" system on it. It sounds very 70's muscle car ish. I can stand 2-3 feet behind the pipe and the exhaust will cause my pant leg to flap. I know I am giving up some ponies but it is a rag top speed is not main goal.

Before I did anything else I would take the car to a well known dyno tuner. He can make sure the tune and timing curve are spot on. Even if you had it done before it WILL be different going from manifolds to headers. He will be able to set your fuel mixture and set the time curve. This can make a huge difference in how the engine works and sound. The most common comment I hear after guys get a dyno tune is "why didn't I do this years ago"

After that and you are still not happy with the sound then start changing things.

 

Well considering you shifted at 2000 rpm they sound good. Get on that thing and report back,those super 44s are very deep and throaty .