HP limit with 1-5/8 headers

GotDart said

To put that another way, just because a TTI step header works wonders on one guy's 7500rpm screamin' 340 does not mean that same header will perform as good on another guys 416 stoker with a 5500rpm readline.

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Just for reference, I shift a little over 6,000 and go through at around 6,500 rpm. My compression is less at around 10-1 and heads have OEM ports, but the rest is similar.

For what it's worth, my opinion on stepped headers was influenced by the fact that many of the high-rollers in NHRA and IHRA Stock spend a lot of money and dyno time getting custom stepped headers made and that's one reason they have VERY fast race cars within the rules! While I'm not in a position to do that, I got these after seeing magazine tests and the same headers on other cars in my class performing very well. And these are "on-the-shelf". They work well on the track AND on the street!

Like any part, adding it may alter what the rest of the combination likes and may require some fine tuning. (i.e.: jetting, ignition timing, etc.) "Shelf" parts aren't "perfect" for many combinations. But they are usually designed to work well in a wider variety of applications. So GotDart is correct. But getting that perfection is beyond most of our resources. (Design, build, dyno, track, redesign, etc.)

Unfortunately, TTI doesn't have headers for the early A-bodies. Also, the 1 5/8" headers won't make the combo run "bad". Sometimes you just have to make the best of what you have. But if it becomes feasible to get different headers, a bigger size would make an obvious improvement overall in 66dartman's combo.