So i decided to do a 6-liter tune on my truck. But im working with a guy that races mud trucks and is a machanic.... He has been doing this stuff for 15yrs or so and used to build cars to race in the 1/4 mile. He says that you cant adjust the timing just by turning the distributor but instead probably through a computor, so he asked me to go online and find out if he is correct. Ive done everything for the 6liter tune except the timing because he said that, on my engine, you can set the base timing on the engine which will basically just change the idle, but under load when im driving the computer will adjust the timing back to factory specs. But many people on here say that they have advanced the timing and it makes quite the difference. So can someone please explain how the system on my 1993 4.9l works in reguards to timing advancement?? Also chime in on if this will affect the engine's reliability in the long run....

 

The computer only has one input of the engine's position, and that is through the distributor's camshaft position sensor.

All timing adjustments are based on the computer assuming the distributor is set to 10* BTDC. If you advance the distributor to 13* BTDC, the actual advance will be an additional 3 degrees at every point of operation. The computer has no idea where the distributor is timed.

 

So if i advance the timing it WOULD make a difference in power... How would that affect it in the long run?

 

It wouldn't affect it negatively, if that is what you mean. As long as you only advance it a couple of degrees, and not enough to cause knock.

 

there is plenty of people on here that have advanced the timing on their 4.9l I myself have it at 12° on my 93 4.9l

 

Did you notice a difference in mpg or power when you advanced the timing???

 

Most computer controlled ignitions get their position signal from a crank sensor. Turning the distributor on vehicles with that setup does nothing for the timing (if it's even possible to do). Since these trucks have a computer controlled ignition, most people assume that you can't change the timing by turning the distributor. But as Lead Head said, on these trucks the computer gets it's position signal from the distributor, so turning the distributor does change timing, just like it used to.

 

yes I got 1-2mpg better. ran a bit smoother too