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Original Message
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| They are actually closer to C6AE-R heads. |
| By Dave Shoe - 02/06/2003 5:44:02 PM; IP 12.104.160.195 |
As long as you only need to use the vertical exhaust bolts (as I believe is true on boats), you are correct in stating 352/390 heads will suit your needs well.
I would recommend any common production 1959-1965 heads, as these are all exactly the same (in my opinion), and will flow just slightly better than the C7 marine heads because they lack thermactor bumps in the exhaust. Yes, the chamber and valves are the same on these heads as on the C7JE heads, and the runners are the same, except for thermactor bosses.
You may want to avoid mixing in C6 and later castings (except C6AE-R and CJ), as these tend to have small "emissions" type runners and slightly smaller combustion chambers. Having said this, emissions heads would perform great for a stock 300HP marine motor, particularly since your friend probably has the matching "T" marking on the #1 intake manifold runner, indicating the manifold is designed for small runner 1966-later emissions heads.
I suspect new heads are around someplace, but I haven't seen any sold for a while. You'll probably have better luck looking for used heads. If the valves are sunk in the heads you buy due to too many valve jobs or use of unleaded gasoline under heavy service conditions, you may wish to install hardened valve seats. Note also that small runner "emissions" type heads also accept hardened seats very well.
When it comes to used heads, one concern will be whether the head has been milled. The most accurate way to determine this is to measure from the deck to the center of the intake manifold bolt holes. No other deck reference has quite the positioning accuracy of the intake holes.
JMO,
Shoe. |
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