Rocky here, already have the 302 in the surrogate 75 Mav just to test it out (6 cyl)... it's going in the the 76 Mav (250). Question: Wiring harness, from 6 to 8: Why, from what I've read in the forum, do you have to change the harness from firewall to distributor, etc? I installed the 302 using the 6-cyl harness and fired up no problem. The only difference I seen was on the 6-cyl going to the distributor connection was a 3-prong, the V8 was a 2-prong. What is the the 3rd prong for in the 6-cyl? Bottom line is, why does it have to be changed? (wiring harness) Fire hazard?
It has to do with the routing of the wires. There isn't really a problem using the 6 cyl parts like wiring and throttle cable, for example... Just that the V8 parts fit properly. If you use the 6 harness, you might find that you need to modify the temp and oil sender wires to reach, just to name the obvious, but there might be more. The pin difference is more a matter of years than cylinders. 74-75 have 3 pins IIRC, and 76-77 have 2... That explains that. Has something to do with a function of the box that was integrated better in the later year models. I'd have to dig up my DS book to remember exactly. One problem though, is that every year of electronic ignition in our cars, Ford changed wire placement and colors! So you have to be very careful when mixing DS parts.
Duraspark ignition system. Sorry... In 74-75, Ford called the electronic ignition "Solid State", then in late 75 or 76, they started calling it Duraspark and Duraspark 2. (DS 1 was only in Kalifornia, and for a very short time.) Most folks just call them all Duraspark, or DS for short. They are all very much alike and only small changes distinguish one system from another. One of which is the swapping around of wires. So where a positive wire was one year, might be a negative wire another year... yet the plugs are identical. Doesn't really do anything but run your coil at reverse polarity... Hurts spark, but will run.
Thank you for the info. So it will run, but not run right? Correct? So what do we need to do? Not electrical wizards here, eh. Supid, eh!
Well, I am not saying you have it wrong... I am just pointing out that you could run into issues with mixmatch wiring.
