D0OE Heads

Change the expansion plugs out for the marine (brass) ones. Have your valve springs checked or have them replaced. A good cleanup and valve job to freshen them up and don't forget to use a good quality marine head gasket.

reid I believe they opened up the combustion chambers on the later castings, for the D0OE heads to work nice you have to replace the exhaust valves with larger ones and work on the runners too. Really he shouldn't see that much of a gain just a little due to the higher compression.

you'll see about a 10 cc difference in the chambers and the largest ex valves you can use are 1.60 they are around 1.45 stock I believe. But most of the work needs done on the bowls and runner for the ex.

Chris, I think you're right on in terms of the 10cc smaller chamber size, which should provide a full 1-2 point gain in compression. The original size valves in the D0OE heads are 1.84 and 1.54, as the later 351 heads shared the 302 sized valves. Also as you noted, historically the stock Ford heads, even the the GT40s have comparibly small exhaust ports and runners, so I concur they could use some help there also. But apples to apples, by virtue of the compression hike and at least a little increased flow I'd bet there's 20-30 HP there. See the two links below for good head to head comparisons on a multitude of small block Ford heads as well as a great document on GT40Ps. For comparison's sake, the later model 351 head is most closely in design to the 289 head shown. The GT40P info gives us the answer as to why jbear's boat is running like a rocket.   
http://www.mustangii.net/head.asphttp://www.stangpro.com/html/articles/gt40p_files/gt40p1.htm

Guys; I am sure you all know that I have no idea what all this tech talk means. What I do know and Backfoot can attest to is......the '80 just runs like a rocket now with the heads Reid is talking about and the manifold I got from nutty. All you need is great friends like I am lucky enough to have that'll put this stuff on correctly for you.

john