BADSS

iTrader: (7)

I replaced my TR 224 cam with the FMS F11 (228/230 .577/.596 112 LSA), and lost 12 HP and 10 RWTQ on the dyno- after tuning. I am seriously bummed, and looking for an explanation. I know my heads aren't very good (JPR S2), but even stock heads pick up power from bigger camshafts, so how did I lose power? Valvesprings are brand new Patriot duals, so they can't be the problem, I wouldn't think.

Before numbers with TR 224 cam: 420 RWHP, 400 RWTQ.

After numbers with FMS F11 cam: 408 RWHP, 390 RWTQ.

Used the same dyno both times. The curves look almost identical, but the TR cam is higher everywhere. A/F ratio looks good, no KR detected.

Besides the heads, the only part of my combination I am doubting is the YT roller rockers- but they were on there with both cams, so that doesn't explain the power loss. Both graphs show a dip in power around 6700 RPM's, but my tuner thinks the heads hit a wall here rather than it being valvefloat. It did it with both cams, and with both the Crane dual valvesprings and the Patriot duals. TIA for any and all suggestions!!

jlaw

Strange. Where are your peaks with the F11?

gomer

iTrader: (13)

I'm guessing the JPR heads are getting turbulence at the higher lift numbers of the new cam. They probably were ok in the low .500 lift range, but went to hell when you got close to .600, that's probably the dip in the dyno graph you are seeing.

BADSS

iTrader: (7)

Where should the power peak with the F11? My curve is very flat from 5800-6500 RPM's, so I can't tell exactly where it peaks.


Gomer- I had similar thoughts about the JPR heads, but wouldn't the same be true of stock heads? They seem to always pick up from bigger cams, even gonzo cams like the T-Rex.

Maybe my heads are WORSE than stock heads.