Gessford Machine, whom I bought all my parts through mostly for access to the knowledge base that came with them, estimated I gave up about 150 horse.
It is difficult to FEEL the difference! It can be measured however. I went from 11.90 solid roller to 11.99 flat tappet. But it wasn't all the cam, custom pistons added quench so I could run more advanced timing. Compression ratio dropped from 12.5 to 9.6 to run pump gas. Smaller carbs, along with the other mods, doubled my mpg, that is significant because it means my effective cruise range per tank of gas also doubled!
Once you have enough h.p. to reach traction limits h.p. above that amount is "interesting" but if you can't hook it up, it's not practical. Shift points fell from 6800 to 6200 rpm. I usually shift at 6000 anyway, just to save the motor. I'm in this motor for the long haul, not a season of racing.
Why wouldn't a professional engine builder recommend a flat tappet? That's easy, I wouldn't either! To much hassle and risk with the break in. WAY easier, less risk, longer warranty and more income to recommend a hydraulic. Now a real man... OK, I won't go there.
