Headers vs 340 manifolds

65 Cuda 340 said
Had to check to make sure I had not already posted in this thread. Back in the late 70s-early 80s, I had a 73 Duster 340. Stock except for a spread bore Holley, it ran 15.05 at about 93-94. Put on a cheap set of Black Jack headers, no other changes, ran 14.40s at 98 despite now having a serious traction problem with its open rear (3.21 ratio). Just a sure grip would have got me into the 14.20s. I was amazed at how much faster this almost totally stock low compression motor was with headers.

Fast forward to 8-10 years ago. I sold the early model 340 hi-po manifolds I was running on the 360 in my 67 Barracuda, got rid of the muffler shop 2.25 exhaust and replaced it all with TTI step headers and TTI 2.50 inch X-pipe system. Again, a low compression motor, albeit with thin head gaskets and heads milled.030 (but the pistons are .100 down at TDC). Cam is a Mopar Performance 761, which is basically one step above stock. Again, I was amazed at how much more power it had - everywhere. No traction at all anywhere in low gear; had to swap to drag radials (for the street) because it was scary to drive with street tires (I think roads around Tallahassee are slicker than farther north, maybe heat/humidity). No times, because I haven't been to the strip since, but no question it was a huge improvement.

So then I bit the bullet and put TTI headers/2.5" exhaust in my 65 Barracuda. Now that was a job. Cam is the same as in my 67 Barracuda, compression ratio is higher. Again, big improvement.

So, I simply don't believe any test that says headers are only worth 10 hp. Maybe with a .380 lift cam. ??

Just my own experience. Yours may differ.

The difference that you saw with headers is that headers usually produce more power all over the RPM range with no loss of power anywhere. Most people just look at peak power production and see 9-10HP at 5,500 RPM and think that they are not worth it for 10HP, and to be honest a lot of performance parts that only make 10 peak HP may not really make much of a difference as they only make that power on the top and usually lose mid range torque, like with a single plane intake on a very mild engine. Another thing with long tube header that usually improves, and the dyno cannot account for it, is that you get rid of some of the bad horrible bends and kinks in the tubing right after the exhaust manifolds, that in itself will probably make a good improvement, that you will not see on a dyno, as you are not running stock exhaust tubing. Parts that make more power all over the RPM range, from 2500 to 5500 usually make a good difference in performance. I learned this while working on 5.0 Mustangs in the 80's and 90's. One of the most popular performance accessories, and the one that when I sold them everyone said that the car felt much better and when I drove them after the install I could always fell the difference, were underdrive pullies. The underdrive pulley kits, crank/water pump/alternator, would only make maybe 5-6 peak HP on a 5.0 engine, but the cars definitely felt much better and were faster. The pulleys would make more power from idle to redline, and even though it was not a ton, it was everywhere in the RPM range with no loses anywhere.