Hmmm whats a spout connector? And 31x10.5 are smaller than stock 275/75.

 

You're right. But once the engine is running, the computer has got control of it... as evidence of this, go loosen your distributor, hook up a timing light, and start your engine... observe the timing marks as you move the distributor around... the computer compensates and does with it what it's going to do regardless of distributor orientation.

The book tells you to disconnect the SPOUT and set the initial at what's on the sticker, I generally use 10° BTDC.


SPark OUTput.

These are in different places in the wring harness but are generally close by the distributor:



That plug should be inserted in normal operation, remove it only for setting the base timing (for easy start-up).

 

Alright awesome! Maybe if i get a day off next week ill go check the timing and compression. And thank you for the picture! I dont have a chiltons manual yet so this helps alot!

 

Yes and no. Once the SPOUT is put back in the computer will change the timing. But at least on the 460 in my '97 F-250 it only changes it by increments off the base timing. It works exactly like the vacuum and centrifugal advance in a non-computer controlled ignition system. If the base timing is changed, the timing at every point in the computers timing map will be changed by the same amount.

On my '97 EEC-IV 460 the SPOUT is close to the driver's side hood hinge, so the location can vary. I don't know where it would be on a '93 302

Yes, remove it only for setting the base timing, but base timing affects way more than just easy start-up. As I said above, it changes the timing at every point in the operating range, so it affects power, knock and mileage.

 

It is not designed to operate that way; I forget the details, but it uses multiple signals from multiple places to determine what the timing gets set at.

If you perform the test I described above, the timing *should* remain relatively static as you move the distributor around.

 

Well i figure if i follow the directions per sticker on the hood i should be alright..Otherwise i doubt the sticker with directions would be there lol...So am i correct to assume i should get a new thermostat being it takes 10 miles of driving to warm up? I understand i can test the thermostat in water but looking over reciepts it hasnt been replaced in 15yrs.. so probably due.

 

Well, one of us is wrong, and I still don't think it's me. I know that if I advance the base timing to 16 degrees the truck will knock when accelerating, and if I dial it back to about 13 or 14 it doesn't knock. So I know that the base timing does affect the running timing on my truck.

From my understanding the computer does not "determine what the timing gets set at", but only determines how much to change the timing. Yes there are multiple signals from multiple places, but I'm pretty sure that the only place the computer gets any signal that tells it where the crankshaft is in its rotation is from the distributor. So moving the distributor changes the computer's base as well.

Again, I'm talking about an EEC-IV system on a '97 460. The OPs '93 would also be EEC-IV, so it's likely the same as my truck, but an OBD2 may well be different, I couldn't say about that.

 

Actually stock would have been 235/75r15 or approximately a 28.9x9.25... So a 31 is about 8% bigger.

 

Hmm weird.. old dealer paperwork said 275/75.. Eh any rate tires arnt that big of a issue for mpg in this case.

 

Correct, the only reference the computer has on all of these OBD1 EFI trucks('86-97) for crank position is the PIP module inside the distributor so it must be set correctly referenced to TDC on Cyl 1, then the computer will advance timing a set amount from pre programmed ignition maps based on the engine load it calculates using the engine sensors .

 

So i finally got to checking the timing... it was set at 14deg ATC... I adjusted it to 12 Deg BTDC now. So driving back its got way more torque and horses but i keep hearing a noise that i didnt hear before its a very faint clunking noise... And last fill up i got 140 miles for 11.8gals

 

Cn you describe this noise in more detail, and when it happens? Does it happen on heavy acceleration under load or from a dead stop/really slow speed?

 

Happens all the time the vehicle is moving wether it be coasting in neutral or accelerating. And it honestly sounds like a mudflap slapping metal its a deep clunking that is every 2 seconds

 

Does it slow down and speed up as your MPH changes?

 

Yes and no. Bigger isn't always better. Exhaust velocity increases efficiency, increased efficiency increases torque and max torque happens at max VE efficiency. Increase in volume=decrease velocity; decrease velocity=decreased scavaging=decreased efficiency=decreased torque=decreased power and MPG.


I'm not going into all of the fluid dynamics behind airflow through an engine, but there is an optimal exhaust size and length for a given engine (and type) at a given RPM for max efficiency. A decrease in pipe size increase velocity. It also increase restriction but it is NOT restriction that increase torque and power. (IN this case; I'm not going into fluid dynamics of every type of engine in every time of configuration in every type of situation)


You need an exhaust with more velocity, not restriction.


Increase volume=decreased velocity. (it also decreases restriction but that is secondary)


Increase velocity=decreased volume (which raises restriction which is again secondary.)


It's a common misconception in situations similar to this, that; "You need more back pressure" when is fact more velocity that is needed; the restriction is secondary.


This is a simplified version painted in broad strokes for the sake of brevity and clarity. I'm not getting into a discussion of where this is or isn't applicable and to what degree in this situation as well as others.


I'm not saying this is the sole source of your problem; just answering the queston asked thereof.