Questions and Answers

Ford Mustang Engine Transplanting
Q. First let me thank you for taking the time to answer my question. I am currently working on a Ford Mustang, I believe it to be about a 1980. I am not much of a Ford person but have tinkered on several before.

This one is for my nephew who bought this car with the hopes of having a car to show off to his friends. Standard teenager.

Anyway, I believe it started out with a four cylinder engine and then got swapped with a 5.0 liter HO V-8. Whoever swapped the engine went to a lot of trouble to put the new harness in the car along with all the necessary vacuum hoses and the high output fuel pump.

Well the motor never ran correctly so we are in the process of replacing the motor with a 351, which we have in the car now, but the wiring harness is very different from the one that ran the 351. I believe the 351 is out of a mid 80's Ford Crown Victoria. I think it was a cop car.

My question is this, do we need to get a wiring harness for the 351 and put it in the car to get it to hook up the right way? I realize the fuel pump will need to come out of the car because the fuel pressure for a carbureted engine is much lower than that for a fuel injected engine. So we are going to run off the engines fuel pump. I am not sure if the computer for the 5,0 will let the 351 run right what are your thoughts on this?

The distributors are also different the 351 is a older style HEI and the 5.0 has the module built in it, making the connecters different. We had the wiring hooked up to the older style module and could get power to the plugs but couldn't get the engine to crank over with the key.

So somewhere we do not have something right making me think that changing wiring harnesses may be the way to go to eliminate all the unnecessary pile of wires needed to run the fuel injected engine we took out.

I use to work in a dealership as a mechanic years back but never dealt with this stuff before. It was a GM dealership. Anyway, any advise you could give would be great.

Thank you.
Dan

A. I can only imagine the pile of spaghetti you must have under that hood. The only thing missing is a nice marinara sauce.

I think at this point the best thing to do is to remove the harness from the car completely and replace it with the one from the donor vehicle. This would include the PCM and ignition module. There were two different ignition modules used for that ignition system, but I would assume the donor vehicle would have the correct one.

You will never be able to make the existing harness work with this engine without doing MAJOR surgery to it, assuming it is possible to make it work. Sometimes the best thing to do is start from scratch.