Eight cylinder heads, a pile of intake and head gaskets, and two days on the dyno produced
Some cynic once asked, “How can we miss you if you won’t go away?” The same could be said for the venerable small-block Chevy. Every time we think we’ve come to the end of the Mouse motor saga, another good idea crops up, and we’re back beating on this little engine on the dyno. Our latest adventure involves a quick test of eight pairs of small-block Chevy heads tantalizingly priced at less than $1,000. While declaring a “winner” based on a simple nod to peak horsepower would be the quick and easy story, we planned to do more than just flog the obvious and call it a day. Instead, we have dyno curves, average power comparisons, and even dollar-per-average-horsepower evaluations. We’ll give you a thumbnail of each head and then show you the dyno numbers. With this broad of a selection, the only hassle might be choosing the best pair of heads. But the good news is that you will have plenty of information. Most of these heads offer a power increase of around 40 hp, and even the iron Vortecs were worth 20 hp over stock. The two best heads in terms of peak horsepower were worth more than 60 hp. But, as you’ll see, there’s much more to the story, so read on.
With our Slayer 350ci small-block back up on Westech’s dyno, the flogging began. To help w
The first thing we needed was an engine on which to evaluate power. Since this was a low-buck head test, we decided to use our budget small-block 350 Slayer engine from the May and June issues (“Saturday Night Slayer” and “How to Run 11s”). The engine began life as a Goodwrench 350 crate engine that we pumped up with a mild Summit Racing hydraulic flat-tappet camshaft and then abused with a 150hp nitrous hit. The cam and nitrous were worth a whopping 525 hp, and nothing hit the floor! Not satisfied, we yanked it apart, added a set of Federal-Mogul forged flat-top pistons and iron Vortec heads, and dropped this package into our Orange Peel ’66 Chevelle. That combination ran 12.86 at 105.64 on the engine and low 12s at 115 mph on the nitrous. As you’ll see, the Vortec-head combination was worth barely 378 hp, and the top five heads we tested would easily push the Chevelle into the mid-12s without much difficulty.
We knew the thrash would really abuse the head-bolt threads, so we used a set of ARP head
We pulled the engine out of the Chevelle and stuck it on the dyno, still with the Summit flat-tappet cam and the Scoggin-Dickey–modified Vortec heads. We retained the Edelbrock Performer RPM intake on the engine and ordered a standard small-block Performer RPM intake for the remaining tests. Since most of these heads would benefit from additional lift, we also added a set of Harland Sharp 1.6:1 roller rockers that bumped the lift up to roughly 0.500 inch of valve lift. While some of the heads offer good flow at 0.600-inch valve lift, we never got close to that with this cam. That would have required a roller cam, which we decided against because more than half of the field would have required a valvespring change. As it was, we were forced to use 1.5:1 rockers on the stock iron baseline heads because retainer-to-seal interference limited valve lift to the 1.5:1-rocker-ratio lift numbers. We also flow-tested all the heads, see the Budget Cylinder Head Flow Data article attachment just below.
|Camshaft, Summit (PN 1105)
||Duration at 0.050
||Valve Lift (With 1.6:1 Rocker)