We should publish this topic on the website somewhere since it comes up so often.
Bill Carroll's Ford V8 Performance Guide ( the Stockers Bible ) says: "which makes little or no difference because of lowered compression ratio" when 351w heads are put onto a 289 as part of his stage 2 upgrade to a 2 bbl 289. Stage 1 was an upgrade to an aluminum hi rise manifold and 4 bbl 600 cfm carb and a mild hydraulic cam. Stage 3 included hi compression pistons and stage 4 included a mechanical hipo cam which all together yielded 339 HP from the 289.
Stock, the 351w heads do outflow the 289 head on the intake side, but the exhaust side is the same or worse due to thermactor humps ( if you have post 65 289 heads, you have thermactor humps on them too ). More flow is possible from the 351w head than a 289 head if you are willing to port them. At a minimum, remove the thermactor humps from the exhaust ports. Fully ported, they'll flow just shy of 220 intake and 180 exhaust.
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Tracy Blackford: Corona, Ca
Restoring '65 Fastback Mustang
329 with stage II 289 rods, KB 322 pistons,
282S cam, and race preped 351W heads.
<font size=-1>[ This Message was edited by: blkfrd on 9/4/03 11:38am ]</font>