Here is the 455 engine with...
Here is the 455 engine with the Hedman long-tube hedders set up on the dyno.
Did we raise more questions than we nailed down answers?
Once upon a time I had this idea: While strolling the aisles at SEMA last November-the largest automotive aftermarket trade show in the universe-amongst all the glitz that is Vegas, I spied a set of hedders (that's how Hedman has always spelled it) for a Pontiac. But these were different; they were shorty hedders-a style made famous by late-model Mustangs, Camaros and Firebirds.
They were certainly something new and different for the traditional Pontiac engine, so of course I decided that we should test a set. In speaking with the Hedman reps, I was informed that the display models were prototypes and that sellable versions should be ready after few months. In the meantime I had to get an engine and a dyno facility, and come up with parameters for the test. I felt that the real questions in everyone's mind were:
• Where in the performance ladder would these hedders fit?
• Are they better than stock log manifolds?
• How do they compare with H.O. manifolds?
• Could they possibly be as good as full-length headers?
• Well, there's one way to find out and that was to test them.
A 389 Tri-Power engine had been going together at Jim Taylor Engine Service for some time. We covered the Tri-Power unit's build up and the changeover to screw-in studs for the heads in past issues and the engine was nearing completion. Scheduled to make about 400 hp, I felt that it would be great for testing the shorty hedders against a set of Hedman long tubes, a set of reproduction ram-air/H.O. manifolds and a set of stock log manifolds.
This bird's-eye view of the...
This bird's-eye view of the dyno console reveals all of the controls and gauges as well as the computer for this Stuska unit built by Hoffman Machine.
After jockeying for parts, we finally procured a set of shorty hedders and a set of 1.75-inch diameter long tubes from Hedman. Both sets were metallic ceramic coated (called HTC High Tech Coating by Hedman). Jim Wical at Hedman also warned that the shorties don't do much on a stock engine. I assured him that our 389 was not stock. Performance Years provided a set of ram-air manifolds featuring 2.25-inch outlets and Jim Taylor had the factory log manifolds. It appeared that we were ready.
Taylor made arrangements with Bitner Automotive in Trenton, New Jersey (609-888-1199,) to do the dyno work and a date was set. HPP contributor, Jim Dietzler, covered the test. Because of a miscommunication between Taylor and HPP, the 389 engine ended up with much less cam in it than we had originally planned. As Jim explained, the customer who purchased the engine in the interim wanted more docile street manners so with the Hedman long tubes installed, the 9:1 compression 389 pumped out 367 hp at 5,400 rpm with 407 ft-lb of torque at 4,350 rpm. Basically, we had Tri-Power engine making stock horsepower yet I promised 400 hp to Jim Wical at Hedman. So we took advantage of the situation that we had and tested the long tubes, the shorties, the ram-airs, and the logs on the Tri-Power engine to learn how they affected a nearly stock powerplant built for low compression.
Fred Bitner of Bitner Automotive...
Fred Bitner of Bitner Automotive and Jim Taylor and Mark Erney of Jim Taylor Engine Service check out the Tri-Power's carbs during the first hedders vs. manifolds test.
At this point we had half a test as far as I was concerned. Knowing what these pieces will do on a stock engine is nice background information but what we really want to know is how they compare on a hotter engine. Enter the 450-horse 455 street/strip stump puller that we used for a second dyno test. In setting up the second dyno test, we made one change. The log manifolds were replaced with Ram Air Restoration Enterprises 2.45-inch outlet ram-air manifolds and its 2.50-inch mandrel-bent head pipes. This was going to be a very interesting test. But first let's meet the players.
About The Contestants
Hedman Long-tube Hedders
The Hedman long-tube hedders are a true 4-tube design that feature a 1.75-inch primary diameter and a 3-inch collector. The tube steel units arrived ceramic coated and have fairly thick flanges to ensure a good seal.
Advantages: The long tubes outperformed the shorties and the manifolds in testing on the 389 and the 455. They look very aggressive under the hood and they are lighter than manifolds.
Disadvantages: Typical fitment and clearance issues in the engine compartment and with the ground come with the territory with all long-tube headers. They also require more care and maintenance and can rust through when they are not ceramic coated or properly painted. Installation can require some gymnastics depending upon the headers' application, the chassis, and the amount of options the Pontiac has. They also require custom head-pipes per application.
Factory log manifolds were...
Factory log manifolds were tested on the 389 Tri-Power engine in our first dyno extravaganza. They were not used for the second test.
Fred Bitner makes a pull on...
Fred Bitner makes a pull on the 455 engine with Mark Erney and Mark Bitner observing.
The 1 3/4-inch primary diameter...
The 1 3/4-inch primary diameter Hedman long tube headers outperformed the shorty hedders and the manifolds in both tests posting 367 hp on the 389 and 443 hp on the 455 engine. They were HTC coated prior to shipping and looked great. But by the end of our intense testing the coating had developed some dry patches and the sheen faded a bit.