Hi all,
My truck is a ’93 F350 dump, plow, & sand truck, with 115k hard miles. (Before I got it, it was a municipal truck in Michigan…)
7.3, ATS 093 turbo, E4OD. I use it for plowing/sanding in the winter, and hauling a skid steer in the summer.
Performance & oil consumption has progressively worsened over the last couple years. A compression test showed 2 low cylinders (240# & 185#), one on each side. It has lots of blow-by.
I can’t be without the truck for an extended time, so I’m thinking about building another engine and swapping it in. Since that approach allows being picky about what I start with, I’m looking for advice about what the optimum parts would be. I’m not looking to burn tires off, but rather decent performance with excellent reliability. It’s a work truck, after all.
So far, I’m thinking a late 6.9 to start with. I’ve read that an ’87 is the best one to get, but I don’t know why… What about the 7/16” head bolts/studs vs. 1/2" for the 7.3? I’ve also read that the factory turbo 7.3s were beefier, but what exactly are the differences?
In a nutshell, what would you guys build?

Thanks,
Phy

 

I haven't built my next engine yet, but when I get around to it this is what I'll be doing.

-6.9 block and heads: hot-tanked for cleaning, and magna-fluxed for crack detection
-Hone the cylinders or give a minimum overbore for clean cylinder walls
-Considering a Typefour camshaft, it has a special grind that lowers max torque by 200 RPM's
-Fresh bearings
-New pistons, milled down to lower compression to run more boost
-Fresh piston rings
-ARP head studs
-Victor Reinz head gaskets
-Been reading about porting and polishing the heads for better flow, sounds like a good idea
-Fresh valve springs
-7.3 IDI Turbo valves (I think they were better...could be wrong though!)
-7.3 IDI rockers
-Victor Reinz valley pan gasket.
-Home-brew Grade 8 intake manifold studs to keep the coolant out of the oil at 22 psi of boost.
-Home-brew exhaust manifolds for a better angle for better up-pipes, routed like a Powerstroke. Under/behind the head and above the bellhousing. (Note: truck probably needs a 2" body lift for clearance)

That's a 7.3 powerstroke engine
-Home-brew Grade 8 exhaust manifold studs
-ATS 093 Turbo with 3" downpipe and 4" exhaust
-Ram air, open up the grille for more air
-Rebuilt oil cooler with fresh O-rings and gaskets
-All new gauge sending units and switches
-Motorcraft/Beru glow plugs on manual control
-'93 7.3 IDI Turbo Injection pump with some tweaks from the fuel shop
-'93 7.3 IDI Turbo Injectors, I believe they are BB code.
(Make good friends with the local fuel injection shop, they'll take care of you . My local shop told me they can tweak a pump for me when I'm ready.)
-6.9 Fuel filter header with aftermarket fuel/water seperator
-If you feel the need for a block heater, a tank-type coolant heater would be good. ZeroStart Tank-type Engine Heaters - JCWhitney Though a good set of glow plugs doesn't require the truck to be plugged in...

As a sidenote, there has been some talk about a Moose pump and injectors which are apparently built by a member over on OilBurners. I don't go over there, so I don't know about that stuff. But F250HDXLT has talked about it before and has posted dyno results from using that fuel system. Expensive and out of my price range, but apparently great results.

The basic rule is more fuel and air in and more exhaust out. Find a way to get more fuel in, and get your air in faster with a custom intake.

The '85.5 and later 6.9 blocks have a thicker casting around the block heater. The 85.5 and earlier blocks could have a crack from the concentrated heat from the block heater. I wouldn't be afraid to use an 83-85 block as long as it wasn't cracked...because I wouldn't use the stock block heater, use a tank-type heater.

If you begin with the 87 6.9, you'll be ahead from the start. The 87 6.9 is the best because it already had the upgrade 7.3 style rockers and the later glow plug system, which is apparently superior to the 83-86 system.

The 7.3 block can also be built up. DPS sells a 7.3 head stud kit. If you find a 7.3 that only needs a honing and isn't a victom of cavitation, then you might use a 7.3 instead. I wouldn't bore a 7.3 though, the cylinder walls are too thin in stock form, nevermind shaving more off. If I went with a 7.3 it would have to be in great shape and only need a honing.

 

are the cylinders with low compression next to each other by any chance?
just because you have low compression in a couple cylinders doesn't mean your rings are bad,and you need an overhaul.
it just means you have a problem.it could be a head gasket or bad exhaust valves.
don't jump to conclusions too soon,as this leads to spending more $ than necessary sometimes.
with with such low miles on a diesel engine (100k)and when theses engines are known to go many,many,many times this.bad valves or a gasket is much more likely than bad piston rings and in need of an overhaul.

list all the cylinders with their readings.

 

No, one on the left bank, one on the right. I was hoping a head gasket might explain all the symptoms too.
I suppose it could be a head gasket on one side, blowing into an oil drain hole causing the blow-by, and a bad valve on the other. If I pull the heads, I'd want to have the valves, guides, & seals done before I put them back on, which will take a while. Then put them back on & hope that was it. I suppose I could get another set of heads set up & just swap them. That way I wouldn't have much down time...

 

if your looking for some 7.3 heads i have some rebuilt ones from a 91 IDI. Im in NJ. I know this isnt the place for classifieds but thought Id let you know about them. They were rebuilt about 5 years ago but never went back on the truck. Project never got finished.

 

Thanks IDI, though it'd probably cost a fortune to ship them to Colorado...
Send me an email with what you'd want, and we'll talk...
Phy
phydeaux@myqci.com

 

thats a bummer you can't use oil.because in a gas job,you can see if compression goes up with the oil,then its sealing the rings and you know the rings are at fault.
i'll keep searching more for ya,to see what the guys do.there has got to be a better way than just hoping its in need of a head job.but man.only 100k miles and in need of rings.that engine would have to have been really abused and not maintained.this isn't a 460.

p.s.
you should still list all the cylinders with their readings please.
what other info can you provide as far as history of coolant,and oil change intervals and or average engine temp readings.anything at all will help at least steer someone with experience with these engines in the most likely direction.

https://www.ford-trucks.com/forums/5...mpression.html
https://www.ford-trucks.com/forums/5...-cylinder.html

 

Thanks for all the replies guys!
Here's the compression test:

Front
Cyl 2- 185 350 -Cyl 1
Cyl 4- 310 305 -Cyl 3
Cyl 6- 325 240 -Cyl 5
Cyl 8- 295 320 -Cyl 7

Engine warm, 6 compression strokes each.

I bought the truck in 2004 with 67k mi. off ebay from a wholesale used car dealer, who got it at auction. It came from a municipality in Michigan. One normally thinks that a city truck would be maintained well, but you never know... I've been changing oil every 3k or so. I didn't know about SCA in the coolant until about a month ago, so it's run without that. I haven't had any coolant/oil cross contamination. I have lost a little coolant, which I attributed to a couple minor leaks. No sweet smell to the exhaust, though the burning oil might be masking that...

Thanks for all the help!

Phy

 

thats low.....from the few I have checked...engines companies don't put compression specs out because it is really not needed...it will be obvious if it is low and the fact that a cylinder is low is enough to make a repair the actual reading doesn't mater.

 

thanks for the ideas fellas glad i'm not the only guy lookin to put together a 6.9 idi..have a line on a 85 that owner sweres has bad head gaskets...anything i should look for???????? its 75 bucks comes with a 4spdtrans, tailights radiator and some ods and ends, it missing the pump, starter and alt....

 

Jump on that for $75! All the external accessories from a 6.9 and 7.3 are bolt-up from your current 7.3 engine.
Before falling in love with it, first you gotta bring it to a machine shop and have it magnafluxed to check for cracks. $75 for an engine with a 4 speed attached, I would drive 6 hours each way for that...
Geez, the bellhousing itself is worth more than $75 since they're getting rare to find...that would be my incentive to jump on that. If you go auto, someone here might be inerested in the bellhousing.

As for building a 6.9, there are several members here who have done rebuilds with some goodies. Dave S. is running around 25 psi of boost, and has the weak links a few times. https://www.ford-trucks.com/forums/1...ch-torque.html

I'll look for a few links of his engine build, I know I have them saved somewhere...

 

yea was kinda thinkin the same thing... the 4spd will be up for sale as soon as i pay our heavy equit mec for the 92 7.3 ZF5/ tcase setup...250 bucks..this will be my first deisal/ first deisal rebuild and first deisal conversion.... don't currently own a 6.9/7.3 so i gotta build it right the first time and make sure i don't forget nothing....it will be turbod at some point..but i hear guys argueing about pumps, injectors, turbo boost levels, turbo manufacturars, all of which is like speacking russian or somethin to me....need all the pointers i can get...this is going into a 78 supercab 4X4 thats also getting converted 2 a dually............

 

OFG- I wish I could find a deal like that around here...
I'm going to look for a builder engine, or a donor truck.
What was the last year for the 6.9?

 

Where's a good place to get pistons & rings, bearings, and such?
Are there preferred manufacturers, or ones to stay away from?
What have you guys used?

Thanks,
Phy

 

International would probably be the best place.