I never could figure out why Ford never turned this exceptionally heavy duty engine into a diesel. It's certainly built heavy enough.

 

I don't think it is. It is a thin wall casting. Having said that - it could have been upgraded with expensive casting changes to the block, heads, and probably that expensive forged crank. Its all about the dollars.

 

Did you ever see how that GM 350 block changed over to diesel worked out?


It did not!
IIRC it had issues with head gaskets and that is when it would run. Never heard of one having a lot of miles on them like a motor built as a diesel from the ground up does and still running.
I had a GM 6.2 with 230K when I sold it. At 100K I installed a Gail Banks turbo kit.
I towed 6K lb trailers, before and after the turbo with it so not an easy life.


Dave ----

 

The GM "diesel" head gasket issues resulted from inadequate clamping load by the head bolts, which eventually fatigued and stretched enough to fail the gaskets. Converting a gas engine to diesel is not an easy proposition, as GM found out - the expensive way.

 

The only problem I've experienced with a 300 six was leaky main seal. Other than that, they're amazing engines. Miss my old 300 six.

 

Yes absolutely rear main leaks. Came here just to say this.

 

My grandpa always theorized that the rear main leak was from lugging the engine. He explained it a number of times. I don't understand how the #6 cyl hitting slowly would affect it more than hitting it quickly, but whatever. He was the mechanic not me.

 

Mine, of course, has a main seal leak- about a quart a month- so I'm doing the responsible thing and ignoring it. I've seen dozens of posts about this issue, but this is the first time I've seen it explained like this. Yet, in a way I can almost see it now that I think about it. My 6er definitely does more of a "6-pack wobble" at lower RPM (1000-1500'ish) and smooths out like a sewing machine above 2000 rpm. Given its torque and gearing, I can see the drive train twisting more at lower RPM and perhaps just enough to put more pressure on the seal making it wear out faster than it would in other configurations. So really, maybe it's just inherent to the design- and something to live with perhaps- instead of trying to remedy it?

 

So running my motor between 1000 and 2000 RPM (I shift at 2 or just below) I will have a rear main leak?
High way at 70 / 75 MPH is only around 1800 RPM. ( over drive & 2.75 rear gear)
I dont see that happening because of RPM.

If the bearings are good the crank should not be moving all over the place so the seal should seal easier.
Seals can also get hard and dry out. I would think more so if used for a lot of miles and it sat for a long time before being used again.
Dave ----

 

I have 270,000 miles on mine, and most likely it's the original seal. I can't even get mine to 70-75, lol. I don't know exactly what transmission I have but it's a 3-speed with a super low 1st, a wide 2nd and in 3rd I hit 2500rpm at 50-55mph. I was just thinking that with the torque all on the lower end that "IF" all the components weren't exactly "new" then I can see where it could "twist" a bit, not necessarily a lot, but even twisting a tenth of a millimeter out of center can cause undo wear on a seal- especially in higher mileage engines that don't have all new bearings and such. I was just saying "I can see it," not that it is indeed fact. But with the number of these engines that have seal issues, there has to be "something" causing it that doesn't happen nearly as often in other (V6, V8) configurations. And 6's do tend to wobble a bit which has to be present on the output side as well.

 

I have a hard time buying this theory, even on a high mileage 300. The crank in these things is pretty darn rigid, and it's got 7 main bearings. On something like a 170/200, that only has 4 Main Bearings, or an earlier Chrysler slant-six, I could see it, there's alot more potential for the crank to wobble around like a wet noodle, just due to less support in the design.

Not saying it *isn't* whats happening, obviously enough guys have the issue that *something* is causing it. I've never personally had rear main issues with the 300, just lucky, I guess.

 

And I'm certainly no expert, so nothing I say should be taken as more than just amateur supposition- and just because I overthink everything. But in my exceptionally analytical thought process, (admittedly sans first hand experience), there is SOMETHING about these engines that causes seals to wear out faster than in other engines. I'm not saying I know the answer- I'm just asking questions and trying to figure out "WHY" so many people have the same problem. I mean, Google "Ford 300 main seal" and there's literally thousands of people who've experienced it- and not necessarily at super high mileage. I know a new seal will fix it, I'm just curious what exactly is causing it- not that I can solve the issue- but understanding "why" helps me sleep better at night.

 

Replace the single lip seal with a double lip seal.

 

Yep, the general consensus was that the GM converto-diesels were duds.

Yet a friend of the family loved his Olds diesel and drove it over 200k miles until it rusted out from under him. And then he made a habit out of buying GM diesels throughout the 1980s and 1990s until al the units in good conditions dried up. He got them for a song and drove for cheap for ~20 years.

It helped that he had diesel experience before buying the Olds diesel. He knew their weaknesses and kept on top of the potential issues.

 

My 94 300 is still running strong , just turned 150,000 km [ 90,000 miles] . I use Lucas oil stabilizer at an oil change, the oil level on the dipstick has never dropped. I do plugs and wires, dizzy every 40k [ 25,000 miles ] and air/fuel filters. Regular maintenance on these engines will ensure a long service life. Your mileage may vary.