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I have a set of factory hand ported stage vi heads that made 650 hp and 650 tq at midwest racing engines on a 505 with 13 to 1 compression and a 700 lift roller ....power was all in by 5700 tho ...frankly I like them ..they have their faults tho ....lots better than 915s



Interesting.... Mine are small ports that I purchased from Muscle Motors and then later sent to Dewayne Porter (picts and info in the archives here) for additional work. While I've never dynoes the engine, we've shifted as high as 6200 and not had any gain over the 5600 shift point we've had it set at forever. I run the old tried and true Ultradyne NF 69 flat tappet grind. We did pick up a ton though when we finally removed the M1/850cfm 4150 carb and went with the M1 stage VI 4500 intake and a Carb Shop 1050. Engine is plenty powerfull for low 10 fun and easy on parts.