360 Cylinder Head Comparison

360 Cylinder Head Comparison
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And yet they are neither cylindrical nor head-shaped. Go figure.

The plan was to re-use the stock cylinder heads, perhaps ported slightly. Well, just like any other gearhead, sometimes the Perfect Deal comes along that is too good to walk away from. In our case it was a set of 1974-casting 360 cylinder heads that have 2.02" valves, double valvesprings, some port work, and looks like maybe a bit shaved, all for $200. Later, these will go to a machine shop to be cleaned, magnafluxed, and flow tested; once that money is spent, we'll know whether we got a steal or got took.

Still, until these guys came along, we were waffling between cleaning up the stockers that came on our 1986 engine or adapting a set of Magnum heads. The Magnums fit, though they differ in enough ways that we'd have to pay attention to what we're doing. Paying for high-buck aftermarket heads was out of the question. So, to get an idea of what constituted "good" flow numbers versus "bad" flow numbers, we started compiling this chart.

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.

No.	Head Type	Intake							Exhaust
No.	Head Type	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
1	994 W2 Econo Mildly Ported	N/A	60	127	184	232	274	302	N/A	50	105	154	185	200	208
2	915J Fully Ported, 2.02" Valves	N/A	62	130	186	239	272	277	N/A	52	101	132	166	173	178
3	994 W2 "Econo"	N/A	59	122	182	229	263	265	N/A	51	110	154	173	176	174
4	Edelbrock Mildly Ported	N/A	72	135	191	233	260	260	N/A	69	113	142	164	176	183
5	587 Fully Ported, 2.02" Valves	32	63	126	181	230	253	241	24	57	95	132	132	160	179
6	W2 Mopar Perf.	N/A	69	120	173	215	244	254	N/A	63	113	142	148	151	151
7	Edelbrock	N/A	72	126	179	224	239	242	N/A	66	110	139	158	170	176
8	051 Fully Ported, 2.02" Valves	40	77	137	186	225	228	224	27	52	104	140	159	168	175
9	894 Stock 340X	32	58	125	172	208	221	210	22	45	95	122	135	140	142
10	915J Stock	N/A	66	123	170	206	220	216	N/A	63	110	135	145	148	148
11	140 Magnum R/T	34	70	137	181	209	211	211	24	62	111	142	163	168	171
12	137 Magnum	31	60	118	165	195	209	205	23	54	99	131	167	138	138
13	596 Stock	27	53	107	159	185	199	193	22	48	89	114	121	123	124
14	051 Stock	30	50	113	165	188	193	189	23	49	97	123	133	137	137
15	576 High Swirl	31	62	112	160	182	192	187	23	55	99	119	126	128	130
16	587 Stock	27	52	107	162	195	191	192	22	46	87	112	121	124	126

1. Tony West's Rollin' Thunder website, www.geocities.com/alwest_83/
2. Moparts, Carl's Tech Archive, "974 Flow Test Results, Part 2", 2-19-2002, www.moparts.com
3. Tony West's Rollin' Thunder website, www.geocities.com/alwest_83/
4. High Performance Mopar magazine, 7-1999.
5. Car Craft magazine, 2-2002.
6. High Performance Mopar magazine, 7-1999.
7. High Performance Mopar magazine, 7-1999.
8. Mopar Muscle magazine, 1-2000 & 2-2000.
9. Mopar Muscle magazine, 1-2000 & 2-2000.
10. High Performance Mopar magazine, 7-1999.
11. Car Craft magazine, 2-2002.
12. Car Craft magazine, 2-2002.
13. Car Craft magazine, 2-2002.
14. Mopar Muscle magazine, 1-2000 & 2-2000.
15. Car Craft magazine, 2-2002.
16. Car Craft magazine, 2-2002.

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.