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Discussion Starter · #1 ·
Had my heads CNC ported and milled by a well known performance shop.

Had heads installed and tuned by one of the best tuners in the area (very well known, does outstanding work)

Mods are.

* Ported Fast 102 intake and NW throttle body
* Air intake
* Catless Longtubes
* Cam specs
duration at .050 intake 240 exhaust 248
lobe lift intake .3430 exhaust .3400
gross valve lift intake .617 exhaust .612)
* Mahle forged flat top pistons

With all this the car made about 530 on a mustang dyno.

heads were ported and milled to .020, to get 65cc and using stock gaskets.

First dyno pull the car knocked so bad the tuner had to stop the pull, we thought it was gas at first (car sat for many months) but then I went through 3 fresh tanks and same thing. We even went as far as disabling knock sensors, still lost power.

see attached for photo of dyno sheet. The black dotted line are my power levels before the heads, the red lines are AFTER the heads.

Anyone experience anything similar to this? losing power after heads? suggestions? Things I can check myself? I feel like I just threw thousands of dollars out the window and I'm losing my mind here.

21,394 Posts
That seems really strange to me. I can't see where milling the heads .020 would cause a problem. I'm wondering if you have an intake leak somewhere.
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