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
We raised the roof considerably with a tapered cut limited by the port window and the thin
In an effort to gain more port area in the runner, we considered the available space. The runner has four sides-the roof, the floor, and the port walls. Generally, dropping the floor to gain area hurts flow, so we were left with the walls and roof. The straight side of the wall is constrained by the oil-feed passage and the head-bolt bulge, while the dogleg wall is limited by the casting thickness. We widened the full length of the runner by working both walls, taking care not to cut excessive material in the aforementioned danger areas of the straight sidewall. The port responded favorably to the increased area, breaking the 300-cfm barrier and improving incrementally through most of the lift range.
At this point, finding more area became increasingly difficult. We wanted to avoid cutting the floor, and with the walls widened as far as was practical, the only direction left to go was up. We also wanted to retain the factory port window at the manifold opening, which represents the constraint at the opening of the port. At the far end of the port, deep in the runner, the height was limited by the thickness of the material under the spring-seat machining. Between these two points, the only limit was the casting thickness, which allowed for significant metal removal.
We carefully measured the thickness of the roof at the spring-seat machining and marked the location in the port to avoid cutting too deep in this critical area. The roof between the opening and the marked thin spot under the spring seat was given a deep cut. The depth of metal removal tapered from the port opening (where nothing was removed) to about .150 inch by mid-port, where it tapered again, leaving .080 inch at the near side of the spring-seat machining. It was an involved reworking, giving the roof a concave shape rather than its original flat form. Port flow in the high-lift range improved handily but was out of the range of street/strip valve lifts.
The dogleg wall and floor are shown here after cutting. Note the smooth radius away from t
At this point, the runner size was maxed out, so our attention returned to the bowl area, which, as noted before, was already nicely formed and sufficiently large. In our judgment, the throat area was already near optimal size, and further enlargement of the area immediately under the seat would be a detriment to flow. We lightly blended the bowl as well as the short turn. As we suspected, the bowl area was already well executed in the as-delivered heads, and we saw little benefit in the street lift ranges, though the very top of the curve showed an appreciable improvement.
Our final modifications to the intake port was to break out the cartridge rolls and flap wheels, and polish the port. Polishing removes minor irregularities and further enlarges the port. Again, we saw gains only at very high lifts, most likely attributed to the smoother contour in the port-throat transition and short-turn.
As with the intake ports, the out-of-the-box flow of the E-head's exhaust ports were at a level typical of a well executed, fully ported production head (Table 2). We noted some ridges where the machining of the port exit met the as-cast surface and began our modification sequence by blending the port exit into the runner. However, only a modest improvement resulted.
The large, open bowl needed almost no further enlargement, only a little brush-off to blen
Fully ported and polished, our intake delivered 320 cfm, but most of the gains were up-out
On the exhaust side, we began by removing the "eyebrow" where the exit machining meets the
As with the intake side, the exhaust valveguide boss was minimally intrusive, and profilin
Unlike factory iron heads, the exhaust port has a nice short-turn form. We carved it mildl
Raising the roof .100 inch gained flow up top. However, this is the case only if the cut i
Working the walls a little can give further port enlargement. Note how nicely the runner l
Next, we turned our attention to the valveguide boss and short-turn, mildly blending both in typical fashion. Here, we did find a reasonable improvement from the mid-lift range on up. As with the intake port, the bowl and throat were judged to be good in stock form, so we were reluctant to go for enlargement.
Turning to the runner, the roof was raised about .100 inch, and we gained significantly in high-lift flow. We moved to the runner walls next, taking the outside wall out .100 inch and the inside wall .080 inch. Not surprisingly, we found another increase in high-lift flow, yet the gains were outside of full-on race-valve lifts.
With the runner substantially enlarged, we then approached the bowl, giving it a conservative clean-up and enlarging the port throat by a small amount. Here, we found the flow remained virtually unchanged. The as-cast bowl was substantially open, so there was little to be had in terms of flow by working this area. Adding a full polish to the exhaust port gave us a couple of numbers up top, and this port was done.
Likewise, the inside wall was opened to make a nice transition into the bowl.
This one is pretty simple-the E-heads are a remarkably good value as-delivered for most performance applications. Furthermore, the flow is outstanding in stock form, and unlike some roughly finished heads, the Edelbrocks are not easily improved upon. This is particularly true in the lift range relevant to the vast majority of street or street/strip applications. In more radical combinations, where high lift is combined with big cubes, increasing the port area improves the ultimate performance and rpm potential.
The upside is these castings do not leave a lot of performance behind if you simply bolt them on and go. We could have gone further in modifying these heads, but not through simple porting operations. Possible additional modifications include chamber machining, valve mods or larger valves, or more radical port surgery in the pushrod pinch in conjunction with offset rockers.
However, we don't consider this the real value of the E-heads. In light of the price and quality, they are valuable as they come out of the box for the vast majority of applications. Maybe that's why Edelbrock can't make enough of them.
Work in the bowl area involved little more than a minor cleanup. We avoided opening the th
Fully spiffed-up with a polish job, the exhaust port flowed 243 cfm with a flow tube affix
We had the bragging numbers up to 320/243-cfm on the bench, but in the real world, most of
Edelbrock No. 60189
Tested At 28-Inch Water
*Peak Flow With Pipe