How do you improve upon a good thing? Edelbrock's Mopar head, just as it comes, is a tough
Of all the engine components introduced over the last few decades, nothing has blown open Mopar big-block performance like the Edelbrock heads. Simple, relatively low-cost, and deadly effective, the E-heads have changed the way we build high-performance big-blocks.
In the past, putting up the big power numbers was territory reserved for cylinder-head gurus with the talent to take a chunk of factory iron and whittle it into something it was never designed to be. Face it, in typical street/strip trim, a stock-headed 440 was good for output in the mid-400hp range. Add a full port-and-polish job with bigger valves, and outputs of 500 hp were possible, but these levels were more the exception than the rule.
Enter the E-head. Edelbrock brought big power to the masses in an easy bolt-on package. Open the box on a set, and pump-gas combos in the 500-plus-horsepower range were easy. With some dyno development, we've extracted up to 575 hp on a basic flat-top-pistoned 440 short-block, albeit with a hot solid-roller stick.
So is that it? Do we close the book on Mopar street heads and put away the grinders? An old saying sums up the beauty of hot rodding: "If some is good, more is better, and too much is just enough." On that note, we were curious to know what kind of numbers a set of these alloy wonders could deliver with some judicious carving.
Although the bowl area was about as big as we'd go, there was room to make the runners lar
Porting For Power-The Intake Side
We brought our E-heads to Westech and ran some baseline numbers on the company's SuperFlow 600 bench. It became immediately apparent (see Table 1, Column 1) that these heads are extremely efficient, posting exceptionally strong numbers through the midrange and high-lift numbers that are remarkable for the port size. High flow and modest port size means high velocity, which is typically a blessing, delivering high torque right from the low-end, and sizzling output higher in the rev range.
There came a point, however, where more port size was needed to keep the flow velocity from reaching a saturation point, curbing further high-rpm power production. A careful inspection of the intake port, the intake bowl, and throat area under the valve revealed its generous size. In fact, there was little to improve in the bowl area, with the throat diameter measuring over 90 percent of the valve diameter, minimal valveguide boss intrusion, and a nicely shaped short-side turn.
It was clear from the numbers there wasn't much flow left on the table in terms of "tuning-up" the out-of-the-box finish or executing the basic port form. The ports, as delivered, flowed near what a port of this size can be reasonably expected to flow. We found after careful measurement that the cross-sectional area of the port is tightest at two points-the pushrod pinch point, and at the end of the straight portion of the intake runner. This is the area constrained by the spring seat and short-side turn. Our plan was to increase the size of the intake runner. Generally, porting begins at the bowl, and the runner is reserved for later. However, with the E-heads, the already well-formed bowl area prompted us to work the port backwards, starting with the runner and finishing with a minor cleanup of the bowl.
Our first modification was to enlarge the pushrod pinch point using a Helgesen "E" tool to carefully gauge the remaining metal thickness and open the port width to the max, leaving about .060 inch of material thickness. A great deal of metal was removed with the flow results shown in Table 1, Column 2. We were rewarded with a modest gain in the mid-to-upper lift ranges. Opening the pushrod pinch was an asset, but the minimum cross-sectional opening was still farther down the port. Although our plan was to enlarge the runner, we strayed a bit with the next mod, working the guide boss by narrowing its profile and blending it into the roof channels at either side. We found an incremental gain all the way up the flow curve.
Judicious use of the carbide can reduce the pushrod bulge to nearly nil, but attempting it
The valveguide boss is minimalism at its finest in stock form-a stark contrast to the lump
Port enlargement edged flow upward by widening the port and minimizing the bulges on the s