Stock 340 Manifolds or TTI Shorties?
I've seen the dyno testing that gets posted over and over, where a 300hp Magnum crate motor only made eight more hp with headers vs. hi-po 340 manifolds. (Note that this was a motor whose hp peak was something like 45-4800 rpm, so despite the 300 hp rating, it was a really mild motor.) I can only relate my (limited) personal experience.
1. About 1980 or so, I had a 73 Duster 340 automatic, 3.21 open rear, that was stock except for heads milled .030, a 71 intake and a spread bore Holley. Ran 15 zeros consistently, with no traction problem despite having an open rear. Put a cheap set of headers on it. Had to dent them in a couple of places, they leaked a bit, and they hung down below the tie rods on the driver's side enough that regular street driving partially flattened them. But man alive, did they help power. Went from 15 ohs to 14.40's despite now having so much more low end that now I had a traction problem. Just having a sure grip would have been worth a couple more tenths. More power up top, too. Went from full throttle shifting at 5200 rpm to shifting at 5800 rpm. And all this was with the factory exhaust from the headers back.
2. Despite the power gains, the leaks and the low hanging tubes kept me from running headers again for many years. Fast forward to 2011. Had a 67 Barracuda, mild 360, Torqueflite, 3.23 gears. This was a mid-13 second car, so even though mild, it was a good bit faster without headers than my old Duster 340 was with. Hearing good things about TTI quality, I decided to try a set. Long tubes, because that was all they offered at the time. Despite being fresh out of a three-month stay in the hospital and having a left arm that (at the time) I could barely raise, I got the TTI's in without any problem. They cleared everything, didn't have to dent any tubes whatever, and once in, they didn't leak or rattle. And power? Same as before, helped everywhere, not just up top. This car did have a sure grip, but now would roast the 235/60/15 T/A radials out back from a 25 mph roll, and then start fishtailing so badly I would have to back off. Scared me enough that I switched to drag radials.
So, based on my own experience, I can only conclude that long four-tube headers are worth significantly more than eight horsepower on even a relatively stock 340/360. And a quality header like TTI or Doug's eliminates all the header problems of old. Other than the extra power, I don't even notice that my Barracuda has headers. No rattles, no leaks, ample ground clearance. Spark plug routing as easy as with manifolds. Can't think of any reason to choke a 408 with stock exhaust manifolds.
Edit: I should add that ease of installation applies to 67 and later. Headers are a booger to install if you have an early (63-66) A body. DAMHIK
I've seen the dyno testing that gets posted over and over, where a 300hp Magnum crate motor only made eight more hp with headers vs. hi-po 340 manifolds. (Note that this was a motor whose hp peak was something like 45-4800 rpm, so despite the 300 hp rating, it was a really mild motor.) I can only relate my (limited) personal experience.
1. About 1980 or so, I had a 73 Duster 340 automatic, 3.21 open rear, that was stock except for heads milled .030, a 71 intake and a spread bore Holley. Ran 15 zeros consistently, with no traction problem despite having an open rear. Put a cheap set of headers on it. Had to dent them in a couple of places, they leaked a bit, and they hung down below the tie rods on the driver's side enough that regular street driving partially flattened them. But man alive, did they help power. Went from 15 ohs to 14.40's despite now having so much more low end that now I had a traction problem. Just having a sure grip would have been worth a couple more tenths. More power up top, too. Went from full throttle shifting at 5200 rpm to shifting at 5800 rpm. And all this was with the factory exhaust from the headers back.
2. Despite the power gains, the leaks and the low hanging tubes kept me from running headers again for many years. Fast forward to 2011. Had a 67 Barracuda, mild 360, Torqueflite, 3.23 gears. This was a mid-13 second car, so even though mild, it was a good bit faster without headers than my old Duster 340 was with. Hearing good things about TTI quality, I decided to try a set. Long tubes, because that was all they offered at the time. Despite being fresh out of a three-month stay in the hospital and having a left arm that (at the time) I could barely raise, I got the TTI's in without any problem. They cleared everything, didn't have to dent any tubes whatever, and once in, they didn't leak or rattle. And power? Same as before, helped everywhere, not just up top. This car did have a sure grip, but now would roast the 235/60/15 T/A radials out back from a 25 mph roll, and then start fishtailing so badly I would have to back off. Scared me enough that I switched to drag radials.
So, based on my own experience, I can only conclude that long four-tube headers are worth significantly more than eight horsepower on even a relatively stock 340/360. And a quality header like TTI or Doug's eliminates all the header problems of old. Other than the extra power, I don't even notice that my Barracuda has headers. No rattles, no leaks, ample ground clearance. Spark plug routing as easy as with manifolds. Can't think of any reason to choke a 408 with stock exhaust manifolds.
Edit: I should add that ease of installation applies to 67 and later. Headers are a booger to install if you have an early (63-66) A body. DAMHIK