Working the walls a little...
Working the walls a little can give further port enlargement. Note how nicely the runner leads into the bowl (outside wall shown here).
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...
Likewise, the inside wall was opened to make a nice transition into the bowl.
Our Take
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...
Work in the bowl area involved little more than a minor cleanup. We avoided opening the throat area under the seat, since it was already near optimal at 88-89 percent of the valve size. A throat much larger risks serious loss of flow.
Fully spiffed-up with a polish...
Fully spiffed-up with a polish job, the exhaust port flowed 243 cfm with a flow tube affixed to the exit.
We had the bragging numbers...
We had the bragging numbers up to 320/243-cfm on the bench, but in the real world, most of the improvements were gained high in lift, well out of the operating range for most combos. Edelbrock does a great job prepping these heads for their intended purpose-dishing up a fat serving of atmosphere for the engine to consume.