Originally Posted by
Fast355
It may sound crazy, but you can actually get spark knock from having too little timing. Less timing causes the engine to run hotter, especially the cylinder heads, which can actually lead to more real knock.
Years ago before I was tuning, I put a TBI setup on top of a 305 that had 601 casting non swirl port heads on it. To get it to run well on the stock TBI tuning took 10* initial advance at the distributor. The swirl port heads have a drastically different burn rate than any other head. They burn more quickly than even Vortec heads. Those aluminum heads will want at least 30* of timing in my experience and maybe as much as 34-38*. The calibration for the TBI heads might have 20-24* of timing at high rpm and actually goes negative in places from the factory. Too little timing can cause drivability issues not limited to overheating, no power, backfiring into the intake and more. Best to get the timing curve closer to where you need it to be then work on fueling. Timing changes will affect the fueling on a speed density system anyway. I broad brush more fuel into the tune to make sure there is enough fuel, let the 02 sensors trim out what is not needed while tuning the VE tables.
I have a feeling you will also likely have to lie to the computer on injector size. You have an engine that is probably capable of more than 100% VE near peak torque. You will need to tell the computer that the injectors are smaller than they actually are to get the pulsewidth up enough to be able to control the fuel with the VE table. VE table maxes at 100%.
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