Cylinder Head Comparison
This chart is a collection of published flow numbers for different types of cylinder heads. They are sorted by max intake flow at 0.500" lift, which is frankly a completely arbitrary way of doing it. Our reasoning is that we are looking for high flow at higher rpm. But that doesn't mean that heads higher on the chart are necessarily "better". As a good example of this, note how the W2 cylinder heads are ranked higher than the Edelbrock heads, because at 0.500" lift the intake side flows better. But if you compare the heads across the board, the Edelbrock heads outflow the W2 heads at almost every other point during the cycle. Chances are, the Edelbrock heads probably provide more useable horsepower even if the peak numbers are slightly off. So, it's important to study the complete chart, not just the single data point.

Now, everyone always says that cylinder head numbers are not comparable, that the same set of heads can flow differently on different benches. That is like saying that dragstrip timeslips from two different tracks are not comparable. While it is true that you wouldn't want to treat the exact numbers as gospel, having a look at the flow table at least gives a general idea of what certain heads are capable of producing.

Head Type
Intake
Exhaust
0.05 0.10 0.20 0.30 0.40 0.50 0.60 0.05 0.10 0.20 0.30 0.40 0.50 0.60
W2 Mopar Perf. N/A 69 120 173 215 244 254 N/A 63 113 142 148 151 151
Edelbrock N/A 72 126 179 224 239 242 N/A 66 110 139 158 170 176
894 Stock 340X 32 58 125 172 208 221 210 22 45 95 122 135 140 142
915J Stock N/A 66 123 170 206 220 216 N/A 63 110 135 145 148 148


Factory Casting Cheat Sheet

051     318/360     1977-83
137     Magnum
140     Magnum R/T
308     360 Swirl?  1989-93
587     340/360     1973-74; 1976
596     318/360     1977-83
915     340/360     1970-72
974     360         1975-76
994     MP W2 Econo
As with anything made by the factory, it's important to keep in mind that factory tolerances are not exactly what we'd call "precision machining". Tony West's website has a page that compares several 915J heads and he shows a 50 cfm difference at 0.500" lift between the worst heads and the best. Of course, Mr. West doesn't provide citations for his flow numbers, so it's not easy to verify them. But still, the evidence definitely indicates that factory castings with 2.02" intake valves and a really thorough porting job are able to return flow numbers in the same ballpark as the best performance heads. The question then is primarily one of cost. Who is doing the porting job? The home porter could save a bundle by spending a couple of days cleaning up stock castings. But someone who is not inclined to get dirty might find it more economical to buy the performance heads rather than pay labor charges on a substantial reworking.

Considering the variation in the flow numbers of stock castings, it might be a good idea to have any set of stock castings flow tested after cleaning but before modifying. That way there will be a baseline for those specific heads, eliminating any guesswork about performance gains.

We've also presented a factory casting number cheat sheet. Most casting number sheets list the data chronologically, which is least helpful when you've got a set of heads sitting at a swap meet and you wonder what they fit. Using this sheet, just take the last three digits of the casting number and see where they came from. This sheet only lists heads that were installed on 360 engines, though as the chart shows, the same castings were often used on more than one engine type. Our data after 1983 remains sketchy so we will add to the chart as we learn more.