1989 Ford 7.3L Navistar Diesel

What transmission is mated to this engine and will I need to do serious modifications if I want to change over to a gasoline motor? If gasoline motors will mate up with the bell housing on this transmission, which ones will mate up with no problems? If there isn't a gasoline motor that will mate up, what are the steps to take to make a diesel to gasoline swap in my truck? Change out the transmission? Bell housing?

Bad compression on more than one cylinder on my 7.3L. Is it an easy job to change out rings/pistons/valves if need be and not do a motor swap? Can't find any long blocks at the moment, so I'm considering a 390+ cu. in. gasoline swap. What are you thoughts?

Thanks!

 

replace it with another diesel or buy a gas truck.

 

Add me to the list. +1

 

Unless you're going to go with a carb, you need the wiring harness for FI, complete gasoline fuel system, new exhaust system, etc. Unless the truck you have is in mint condition, most likely not worth the effort, IMHO. Find another 7.3 or rebuild what you have, or just grab a gasser.

 

Gasoline is for cleaning parts, diesel is for internal combustion. I find your idea of a gasoline engine silly and offensive. Lol. Just kidding. I agree with the others. Don't. Buy a gas truck. Or buy another diesel.

 

The diesels have there own sized bell housing, if you get a 400 or a 460 I think that the mounts on the frame should work. If you find the same year of truck and take all of the wireing out it should plug in. The best thing would be to stick the doner infront of your tuck and swap everything.
The other guys are right buying another truck is easier and newer gasser trucks are easy to pick up.

 

Alrighty then. I have canned the idea of changing out the diesel to gas. I will either rebuild or sell/part out the truck. Not gonna go with changing it out. I have compression as follows, starting from the front drivers side cylinder going counter clockwise, the last cylinder in front on passenger side being the last measurement:

300
340
340
200 - ouch?
340
330
350
320

How hard is it to rebuild the 7.3L pre-power stroke diesels? Is there a liquid you can pour in to temporarily help compression?

 

A rebuild will run into some big money quickly, What kind of budget are you working with? I would not want to throw $2k into an engine rebuild on a $100 truck that needs $800 worth of other stuff.
I recently bought a truck with a bad trans for $950. Swapped the good running 7.3 into my truck and couldn't be happier with my "new" truck. Good used engines go for around $500, if you can find one. Patience and checking craigslist every day is what I would do if you have the time to wait.

 

I have never tried this and unless an engine was toast I would never try it, but...... When I was an apprentice I heard an old guy talking about feeding an engine glass Cleaner like Bon ami to improve compression. The theory behind it was that it cleaned and dried the cylinder walls and the rings would seat better. To me it always seemed like a good way to seize an engine. On the other hand I have seen guys pour a cup of water into gasoline engines that has pre detonation caused by carbon build up to steam clean it and knock off the carbon. Sounds crazy but if your ready to yank it you could try. But this is by no means sound advice just heard it years ago from an old nut. Also I picked up a 7.3 short Block for 300 bucks from the classifieds. Sometimes guys don't pay their bills at machine shops and the Shop sells off the guys half built engine cheap.

 

Obviously those compression numbers tell you the engine's still fairly healthy, there is something wrong in that one cylinder. Time to dig deeper, if it's as simple as a head gasket, replace it. Bad valve, look at the seat. If the seat is okay, lap it with a new valve, install the valve and reassemble.

Even if it turns out to be damage to the piston, if the cylinder walls are good dropping in a new piston on just that jug is a budget repair that's doable.

Just keep your fingers crossed it's not cavitated.

 

I made a video (with the help of the wonderful wife of course) and uploaded it for your consideration. Any more suggestions? Here it is:

 

you have one dead hole in there, backed up by the low compression number.
from the sound of it cranking, you may have a bad intake valve.

 

Just my humble opinion but even with a dead hole it should start and run. It would be nice to see the eexhaust in the video. My personal thoughts are of a fuel problem. Like it's not getting any. Was there at least smoke leaving the tailpipe?

 

Yes, it will still run. My '86 had zero pounds in two cylinders and ran.

Sound like you are close in that video, are all the GPs working?

 

Have you had this running since all the fuel system work? Have your wife crank it over(LONG AFTER THE WAIT TO START LIGHT GOES OFF) and give it a tiny shot of ether. The honestly help it along for a a bit with the ether. Not mire than a minute. I have been a diesel mechanic for nearly twenty years and I listened to that video again. I'm convinced there is a fuel problem.