Exhaust Blowout on a Mopar 300hp Crate

Left with the choice of banging clearance into the headers orclearancing the block, we pulled out the grinder and hacked away at theblock. It took quite a lot of material removal to gain the requiredclearance.

The Hookers feature a layout similar to Hedman's full-length tubes, withthe number 3 tube passing up along the valve cover, crowding the plugwires to cylinders 5 and 7. Also, the number 1,5, and 7 tubes are routedlow to go under the steering drag link in the chassis, hindering groundclearance. The 15/8-inch full-length headers provided quite animprovement in torque, with 423.9 lb-ft on tap. At 319, horsepower uptop was down fractionally compared to the shorties. We would expect theresults to be different if the engine was equipped with more camduration, but at this mild spec, the tuning advantage of the long-tubeheader is largely lost up top due to cam timing.

We swapped the 15/8-inch Hookers for a set of tti 15/8x13/4-inch stepheaders. We immediately realized there was clearance for a standardbox-end wrench to be used at the header bolts. The tubes also clearedthe late-block's mounting bosses much better, bolting up withoutbinding, although it was close.

The passenger-side tti header will clear either a stock straightoil-filter arrangement or a production-style 90-degree oil-filteradapter.

The layout of tti's headers is unique, with none of the low-hangingtubes of the other designs and ample clearance for the plug wires uptop. Past experience has shown they have excellent chassis fit. Poweroutput with the tti's was the best of all the systems we tested,clearing 327 hp and producing a healthy 425.5 lb-ft of torque.

With the positive response in output gained by going to the step header,our next change was to determine if even bigger would be even better. Wewent to a pair of 13/4-inch Hooker Super Comp headers. The Super Compsare race-style headers with slip-fit collectors. With this 360's mildcombination, the Super Comps proved to be overkill, with output laggingthe step header, posting 321 hp at 3,700 rpm and 420.7 lb-ft of torqueat 3,700 rpm. As a point of reference, we have seen the Super Comps add10-15 hp to a standard 15/8-inch header in engines of the 450-500hplevel.

Unlike the Hooker street headers, the Super Comps tubes were routedclear of all spark-plug wires.