![]() ![]() ![]() I don't believe you're going to see noticeable gains in a street application with a round port to make the hassle of redesigning your hot side worth it. Description: Dougs Headers D523 2' 4-Tube Full Length Header Pontiac Firebird 400-455 70-74 Metallic Ceramic Coating Item : DHE-D523. Knowing you already have D ports which your hot side is designed around, I'd do either the Edelbrock D port or the KRE D port, which my preference leaning towards the KRE product. Dougs Headers 2' 4-Tube Full Length Round Port Headers Pontiac Firebird 400-455 70-74 Metallic Ceramic Coating (0) Reviews: Write first review. With something like an s480 pumping an additional 14.7psi into it, you're in 4 digit hp territory. That being the case, something like an SD 290cfm KRE D port with a properly sized cam in a normally aspirated 460" Pontiac will typically ring the bell between 550-570hp. I'd be more worried about a factory block holding together than I would be concerned about which port type I'd be using. In fact, I'd bet it would do it on a set of as cast D or round ports if you push the boost up a bit. It was proven long ago that the factory round port heads offer no gains over the D ports, why the factory did this is beyond me, it just made things more. That thing will probably make every bit of 1100 hp.to the tire, at about 15 psi on an aftermarket headed 455, regardless of what head is on it. I believe I've read before you run something like an s480, is that correct? LOTS of "fun".Street application? Probably minimal. You should put headers on a '68 Mustang with a 428 CJ in it. All American Racing Headers are engineered and constructed using 304 Stainless Steel with precision cutting during manufacturing and featuring stainless steel. Every header is tuned with the proper tube size and length to efficiently remove all the exhaust from each cylinder, reducing pumping losses for dramatic gains in horsepower and torque. A short open-end wrench, reaching in from the bottom, is the best way to get those, but the rest can be accessed easily by either a box-end wrench or (even better) a long extension and "wobbly" (swivel) socket from UNDER the car. 1970-74 Firebird / Trans AM 400ci - 455Ci SD/HO Round Port Dougs Ceramic Coated Headers. The involvement of Royal demonstrates how closely linked the dealership was to product development at Pontiac Motor Division. Those are the fourth one "back" on each side. There are two bolts that are difficult on the Pontiac. Having worked in performance-oriented repair shops in the '70s, I put headers on hundreds (literally) of cars. I would disagree that Pontiacs are more difficult than "most" to install headers. If you DO have the long-branch, don't spend a dime on headers. NOTE: If you're not sure about the manifolds being "log" or "long branch", PM me a pic or post a pic, and we can identify them for you. An example of the first generation Pontiac Firebird, in the form of a 1969 Trans Am. Mad Dog also makes very nice headers for the Pontiac and they fit quite well. ![]() 1970 - 1981 Firebird and Trans Am Exhaust Manifolds for HO or Ram Air, D Port Heads, Pair. If they're the "log" type (a straight "tube" with the ports exiting into it, and a small flange where the "down pipe" or "head pipe" attaches), I would recommend the Hookers. 1970 - 1974 Pontiac Firebird or Trans Am Exhaust Manifold Pre Heat Shield. Do the manifolds "sweep" towards the rear and then straight down, with a bend that points the exit to the rear? All in all, about 14" long? If so, very few headers are "better" for power, and none will out-live them. The plain-jane "log" manifolds aren't heavy at all. That is, the "long branch" exhaust manifolds that fit 1st gen Firebirds. If your manifolds are quite "heavy", you might just have the "good ones". ![]()
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