308 vs. x heads

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Both are a good head, but u need big valves and need some port work to ,are them perform good
 
308 i read have better exhaust ports but both will support about 400 hp as is.
which is better on the street...you're probably splitting hairs
but X have 2.02 intakes and "bling"
 
I prefer the 308s but they are visually different (AIR injection bosses) so it might not be what you want. Both will work fine assuming you build them for your performance target.
 
I know a guy who did a lot of testing in the early 90s with x and 308 heads ported unported small valves big valves everything his conclusion was unported 308 with 2.02 valves was a 40 hp gain over the x and ported done right was more but he said the intake port is ticklish and can loose velocity if done wrong. I got a ported set of 308s from him in the early 90s and liked them well. what I know is what I was told if it means anything.
 
From "how to hotrod small block mopars" by Larry Shepard P65.

"They introduced the swirl port 360 with the "308" casting number. Port-wise the "308" casting is the same as the newer "576". both have a similar combustion chamber to the earlier 340-360 heads. Both the "308" and "576" have 1.88" valves, the best exhaust ports and are the best production heads.

P76 (regarding pushrod holes)

"The 308/576 Head.

The '308' head was introduced on the 360 in about 1988 but was NOT exclusively on the 360. Other non-308 castings were also used in these years. So junkyards are not necessarily the best source for these parts. These heads feature the large diameter pushrod hole, to compensate for this the production engineers raised the intake port roof to get more air past the pushrod limit hole. The raised roof offers more horsepower potential. The exhaust port also has a W2 style short side radius and improved shape for W2 type flow"
 
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