Thinking about 1990 7.3 diesel conversion
 

I have 1 1989 F250 4WD Heavy Duty with a 5.8L gas auto trans which I would like to convert to a 7.3 diesel. Found a 1990 F250 4WD non turbo diesel and was curious what issues I might run into if any in converting the 89 gas job to a 90 diesel? The 1990 has 139,000 miles on it and the 1989 gas job only has 87,000 miles on it. I was thinking of rebuilding the engine and the tranny from the 1990 and just putting in the 1989. Any advice to this endeavor? I do have the 1989 Factory Truck Shop Manual which has a section on the 7.3 diesel. Is the 1989 diesel markedly different from the 1990?

the 89 and 90 7.3 is the same engine. at 139,000 miles, unless it was overheated or severely neglected, the diesel is just barely broke in.
since you will have the complete truck to use as a donor for parts, it will be a fairly easy swap.
but you will need to change just about everything. front springs, radiator support, radiator, engine mounts, under hood and in cab wiring harnesses, dash panel, complete fuel system, engine, and trans.

The 1989 F250 Heavy Duty has leaf springs in the front would I need to change those?

351 weighs around 550 lbs wet. 7.3 weighs around 1200 lbs wet.
you put a 7.3 in there with the 351 springs, and you would probable break the springs on the first bump you hit.

Thank you Tom

Just curious, why switch? Is there something wrong with the 90 truck? Different cab type perhaps? That is an awful lot of work and then you have a Diesel engine in a gas VIN truck which is a no-no in a lot of places for registration and emissions. That may not apply in your area I'm just wondering why not fix up the 1990?

Thinking about about 1990 7.3 diesel conversion
 

Ford 834:


Thank you for the heads up on the DMV issue of a gas vin vehicle to a diesel. However, California allows such engine exchanges if you do the following.


1.) Donor engine must come out of the same year or newer vehicle.

2.) Donor vehicle must be in the same weight class as the receiving vehicle (this rules out the Isuzu 4BD1 as those were all put in medium duty trucks with higher weight classes). The CARB guy said that a lot of times the referee will ask for the donor vehicle's VIN or registration, to prove that you didn't get it out of a delivery truck, or a boat! However, he did say that (in California at least) you CAN put brand X engine into brand Y vehicle, as long as you meet these three criteria.

3.) The donor vehicle and engine must have been certified as a California-legal vehicle when sold new.


the 1990 meets this criteria. Additionally, the 89 was acquired at an estate sale and is in pristine condition. Whereas the 1990 was used by an auto parts supplier/garage/dismantler and is basically trashed on the inside and the bed is all sorts of dented. This endeavor is a project where I intend to just do this up. Yes it is a lot of work but I will know in the end that everything works and is done right. You know the old adage if you buy a used vehicle you buy someone else's headache.


Nevertheless I appreciate you comments and thank you.

if the driveline and frame on the 90 are in good shape, i would consider doing a cab/bed swap onto the diesel frame.
it will be easier in the long run.

I agree. Granted, you looked in the CA DMV laws, but that still didn't answer F834's question. Why swap an engines from basically identical trucks? That's like divorcing your wife to marry her twin.

he said the 89 sheet metal is in excellent shape, and the 90 sheet metal is beat to death.

Agreed. If the 89 is cherry then I could see it being worth the swap. It is a lot of work, but worthwhile. I like the body swap idea, but then the frame and cab VIN's would not match. If it were mine I would swap bodies, then carefully transplant the cab VIN plate. Yes I know that is not completely legal but when you legitimately own both trucks... then it would remain titled and registered as a diesel.

Thinking about 1990 7.3 diesel conversion
 

Gentlemen,


There are some truly great suggestions and feed back in these exchanges. I now have some new aspects of this endeavor to take into consideration. The body swap seems to be a great idea which I originally did not consider. Nevertheless I most likely will remove the bed and cab from the 90 which will give a better opportunity to inspect the frame and other details not readily visible. Anything I should look for that should give concern?

Thinking about 1990 7.3 diesel conversion
 

I failed to mention that the 89 has cruise control and the 90 does not. Would taking the cruise control off the 89 and putting on the 90 be an issue?

This is a no-brainer. Body swap all the way.

The only some-what difficult part would be the swap of the dash components, but that's not too bad compared to transfering the "front springs, radiator support, radiator, engine mounts, under hood and in cab wiring harnesses, dash panel, complete fuel system, engine, and trans."

I'd assume the CC would be different cuz it connects to different things on an IP versus a carb (or is it fuel injected?)

I am not an expert in wiring differences in the 8th generation body style, but the following thread may help. One shop manual print screen says 80/89 for cruise control components. You will have to determine if it jives with the 90's diesel wiring loom.

https://www.ford-trucks.com/forums/1...e-control.html


Edit: gas vs diesel should be a matter of the right throttle cable