I think we have a wording issue here. Just because a diesel engine is "based" on a previous gas engine, does not mean that the diesel engine is a gas engine converted to diesel. You can certainly have some common things and dimensions between two engines, but one is definitely not going to stand up to diesel use.

Without doing any research, I would think the diesel block would be thicker in many areas, redesigned for the coolant to oil cooler on the driver's side of the engine, the block oiling system and pump modified for oil squirters for the pistons, and a stronger system to hold the heads in place.

I do know the 6.9 and the 7.3 have a oddball international bellhousing pattern. This is probably the same as the international gas engine. Ford made an adapter to convert it to another oddball Ford/diesel bell pattern(way to go Ford). There are also adapters to go from the odd international bell to a SAE. The school buses and u-haul trucks and dump trucks usually use the SAE adapter to fit the big truck transmissions.

 

Could be but thought I had made it clear the IDI's were not converted gas engines. They used the architecture of the MV (MV stands for Medium V) and reworked it.
International even when so far as to use the existing MV casting patterns for the IDI Block but they were modified for the IDI to keep costs down.

It was not a converted gasoline engine but a redesigned one.

NO major components will switch between the two bolt on yes but not switch, a bunch of smaller stuff does though.

The 5.7L on the other hand was a converted gas engine. GM even confirmed it with this statement when talking about the 350 Olds and the 5.7 Diesel. "All the major parts: block,crankshaft, rods, pistons and lifters have been strengthened to handle the higher compression ratio in the 5.7L diesel".

The IDI's parts were not just strengthened MV bits but redesigned. This allowed IH to build the engine to a price point that was acceptable to Ford and it would have not been possible to do so starting from scratch.

As a 6.9L the engine was near bomb proof as IH had done their home work. When the bore was expanded to accommodate the increase to 7.3L the block betrayed it's gasoline roots with slightly above average cylinder wall flex if casting cores were not perfectly aligned or had shifted, this was compounded by the fact that Ford did not spec or use a coolant with SCA's to negate any potential cavitation issues. IH on the other hand did spec a SCA coolant in their 444 applications.
As a side note wet sleeve diesels can fall victim to cavitation if SCA coolant is not used..

Both the IDI and the MV share the same 2.498" Rod journal Diameter and 3.123" Main journal diameter, bore spacing, head bolt pattern
and valve cover gaskets will very nearly swap (more clearance needed for the Diesels injectors over the MV's spark plugs). They can how ever interchange Cam bearings, lift/fuel pumps, timing sets, transmission adapters, yes it's identical, (the IH guys use the Ford 6.9L T-19 adapter to stuff the T-19 behind an MV ) and a bunch of other bits will physically bolt on to each other.

GM at the time tried claiming that the 6.9L was nothing more than a Gasoline engine with Diesel heads, with both Ford and IH quickly quashing that.
I guess GM was hoping to paint the engine with the same potential reliability issues they suffered with the 5.7 Diesel.

The IDI's are based off the MV engines but to be clear it is NOT just a converted gasoline engine.

 

This above explanation passes the sniff test. it sounds like how a modern american corporation works. i did briefly snoop around on ihc pages and there seems to be a similar viewpoint concerning the mv and the idi.

somehow IHC got it right according to all the ford guys i listened to tell me about the charactoristics of this engine. when this 86 4x dooley was given to me i thought "why not"? i give the old bird a try.
now im hip deep in 6.9l engines (5 at last count) and havent even got one running yet. oy!

charactoristics i heard about

runs forever

fuel efficient
quieter than psd.
parts cheap.
remarkable performance with aturbo
every voice lamented theloss of their 6.9. "wish i still had it " was the general attitude

 

Like most engines, there are a few small things that can give trouble and make people not like them. Getting them started is the main thing, once they are running you are good.

1. The glowplug system. The early glowplug controller is prone to failure. The later controller is susceptible to old wiring connections. Also a lot of the glowplugs sold in the stores are inferior to the original motorcraft/international Beru style plugs. Once you get this figured out, it will start every time.

2. The fuel system. The older trucks had a air/water separator that likes to leak air. All of these trucks have a return system on the injectors that likes to leak air also. Fix the air leaks and you are golden. Most people take the air/water separator off the old trucks.

 

thx.

glow plugs; momentary button switch, routing the wires over front of engine.

fuel system has a complete redesign using electric pumps and a variety of filters down to 4 micron, using the van fuel filter positioning, abandoning the truck fuel filter positioning; using that space for a coolant filter.

been thiinking this through , and thanks to all here on the forum it should address the hairy short comings of ford /ihc design.

 

Apparently, the Olds diesel 350 wasn't just a reworked gasoline 350. Check out this thread at the Oldsmobile site I frequent. Maybe someday I will have to buy myself an Olds with a diesel 350!

https://classicoldsmobile.com/forums/general-discussion/112541-olds-diesel-350-a.html

To the OP I would pull the heads and completely re gasket the block if you have one sitting on a pallet. You might not need head studs if you don't see a turbo in your future, but taking off the heads will let you see if there's still cross-hatch on the cylinders and let you determine the condition of the bottom end.

 

i will.
pan timing cover rear seal etc.
i too am curious about piston condition. but this all is a lot of work.... im going to stud this block too. just because i have them en route from summit already.


TODAY: first start on the 6.9 in the 2wd. ten years she has sat and not been started.
changed fuel and water filter/ seperator.
gonna twist her tail this morning ; see if we can wake the old dog up!

if i can get a bit of tutorial on uploading, i can share a video with u guys, might be fun.

 

Wow I remember being a teenager all the Olds Toronado people bitching because it wasn't a real diesel......

 

Ya the GM guys will try to argue that. But it does not change the fact all GM did was beef up the block and crank use shorter rods and taller pistons and stuff diesel heads on it. (the block would not take the stress of long rods)
Even with these changes they still suffered from broken cranks due inadequate main cap bolt length (gassier length), head gasket failures due to head bolts shearing off, Head gasket failure from excessive block flex this also contributed to the head bolt failures.
Some GM guys will try to pass this off as using green blocks but that just betrays the engine even further as a converted gasser as the architecture was not strong enough even beefed up for a diesel. IH never seasoned the IDI nor Cummins the B series blocks.
IIRC the 5.7L diesel block was nearly identical to the 350 Olds NASCAR block

It is a converted gasoline engine simple as that.. Guys that race Olds engines used the diesel block for lost cost bullet proof and stroker engines, the conversion back to gasoline is pretty strait forward with minimal fuss and even the provision for the distributor was left in the block. Mondello even sold a kits with all the necessary bits to convert the blocks to gasoline usage. And you then have a gasoline block that will easily handle 700 HP.

You can't convert an IDI to a gasoline engine it physically is not possible to do as the block was significantly changed and not just beefed up.
Where as this can easily be done with a 5.7L diesel. That is as good example as you can get of a gasoline engine converted to a diesel. The only other example that comes this close is the 1.6L VW engines available in both gasoline and diesel but even with those you can not convert a diesel block to gasoline.

The 6.2 on the other hand was built from the ground up as a light weight Diesel by DD using features common to the SBC /BBC such as Bell housing bolt pattern Oil filter location etc.

Here is a video of Alan Hoods 5.7L Diesel converted back in to a gasser.

 

I have a 31 year old truck specifically because I need my vehicle to just plain work every time. New vehicle don't offer the same reliability. I can say the same that about both my 6.9 IDI and my 460.

The IDI never left me walking, only one failure when it spit a block heater out which I had pulled and replaced the o-ring a few days prior as it was weeping coolant and apparently didn't notice the cracked T-bar that retains it. Got to a parts store and installed a rubber plug, added water and on my way with minimal inconvenience. One issue in over 4 years, which arguably was my own fault.

In at least a decade I've owned my 460 truck I've had one failure leaving me hitchhiking. The only fancy modern part on the truck failed, the Duraspark module. I hitchhiked home and grabbed another from under my bench (lucky!). If I had an older truck with point and no electronics that failure would not have occurred.

Before I had a truck I drove 40+ year old cars because I needed a reliable vehicle. In the summer I ride a nearly 50 year old motorcycle, because it just plain works every time.

I did have a modern EFI vehicle once, that was an expensive and inconvenient lesson in unreliable vehicles. I'd say the OP has made an excellent choice with an 80s Ford IDI pickup if he needs a reliable vehicle.

 

the 6.9 has a legendary durability record from all ive heard from other ford owners.
this my first go at a v8 diesel,
today the 85 burped spat, and died when we tried to start her after 10 years of silence , she made a bit of noise- long enough to determine the IP was shot, finish putting a newer one in tomorrow.

i never use starting fluid,a point of pride. but i found out today that electrical parts cleaner is a robust igniter of diesel engines
CONCERNING NEWER BLOCK 6.9'S

this truck is technically an 85 model built in 10 of 1984.
but, it has the newer block in it, if the 85 stampings on the heads mean anything FWIW.
no firewall sound blanket either.


QUESTION: why are folks insisting on cold air intakes on these rigs?

seems fords design is plenty good enough 3 inch tube to front grille


nother question ; do these stanadyne pumps dry out if they are off the engine for any length of time?

 

The Ford intake is 3 inch, but then it is squished to a long rectangle isn't it? Mine is long gone so I don't know, only pictures I see on the internet. But I do know these diesels gulp a lot of air, the more cool air you can get in there the better. Many little things are tried on the non-turbo diesels, most with minimal results. Like was mentioned, put a turbo on it and it will feel like two engines under the hood.

The injection pumps do not have many rubber parts to "dry out". They do have some parts that after sitting around can get sticky. People have their tricks to try and remedy this. Most involve taking the fuel filter off, dumping the fuel out, and then putting some sort of diesel cleaner or transmission fluid or some other homemade concoction in the filter, and fill it full strength to the top. Then crank the engine over for a little while to inject this concoction in the pump, and then let it sit for a day or two. This can loosen things up inside the pump.

 

Cold air intake is prudent as these engines tend to run dangerously high EGT. The factory air intake routing is a cold air intake, it pull from the grille area ahead of the radiator. Next to the radiator on 83-86 trucks and above the rad support on newer trucks. There's nothing wrong with this setup, and I don't believe the early setup is a restriction. The alter setup appears to have a smaller cross section and may be a restriction if running a turbo, larger pump, etc... I don't know as I haven't looked at one closely or done any math on them.

Either way, pulling air via the factory cold air intake rather than the hot engine compartment is worth a 50*-100* reduction in EGT.

 

well yes it seems an "un-improvable" design to me. especially considering the engine will seldom operate at a CFM demand that might tax the oem set up. i am especially impressed with the filtration cartridge its huge


QUESTION;
please explain the why behind hot egt on this n/a engine, and are there remedies can be made to an unmodified engine? i.e timing?

 

Ya I'd be curious about that explanation as well.....


When turboed try to keep EGT's under 1150F ,1100F is even better.
Much more than that an bad things start to happen.

Shut down EGT's is best at or near 300F, then you have no worries about coking turbos, etc.

These engines were not designed for a turbo like the PSD was so you need to take that in to consideration.