Removing 4 Zinger Reed Valve

[Zinger2010]

Does the engine of a 4 Zinger YF60 (or Tri Zinger) need to be removed in order to remove the intake manifold and get at the reed valve? I've tried getting a phillips bit on the screws, but can't create enough torque and am about to strip the top of the screw. Any removal tricks are appreciated.

If I can get them out once, I can replace the phillips with a bolt that I can get a better bite on in the future, so I'm not fighting this again.

It's stalling and I've replaced plug, cleaned carb, checked exhaust for carbon (not a problem) so I'm to checking the reed valve and can't get to it easily.

[dcreel]

Getting those phillips screws out is a PITA with the motor out. 3 of the 4 motors I have, they were stripped out, and I had to drill them out. I've never tried to remove them with the engine bolted to the frame. An impact screwdriver will help if they are really stuck.