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View Poll Results: Which is easier to work on and will last longer?
7.3L IDI 5 29.41%
6.9L 12 70.59%
Voters: 17. You may not vote on this poll

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  #1  
Old 08-23-2011, 10:39 AM
mylespowell mylespowell is offline
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Question Pros and Cons of the 6.9 and 7.3 IDI

This is my first post, I appreciate any help.

I am looking for a diesel truck that
1. Will last forever
2. Is friendly to the novice backyard mechanic.
3. Was not over-engineered. (simple is better)

I have been a Ford man all my 25 years, and am thinking that a 7.3 IDI or a 6.9L fits the bill (83-93?).

Any suggestions on choosing between the two? I see that the 7.3 has more torque and hp. Does it get worse mileage? Will it last as long? Is it easier or harder to work on?

I was reading on Wikipedia (yup, a novice) and like that these don’t have a computer controlled fuel injections system and are mechanically driven. I do NOT like the idea of computers. When did Ford succumb to computers? If I say buy a 94 does it have any computer to worry about? I think I want to stay away from them. Is this a good idea?

I saw on the forums that there are two types of glow plug systems for the 6.9L. I am sure they both have their pros and cons. Can anybody tell me the basics?

Also, any thoughts on transmission and body strengths/weakness would be appreciated!

Any thoughts/advice/opinion/fact will help. Thanks!

Last edited by mylespowell; 08-23-2011 at 11:23 AM. Reason: add to questions
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  #2  
Old 08-23-2011, 11:27 AM
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eatont9999 eatont9999 is offline
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The 7.3 is a bored out 6.9 with a few modifications over the years like better rockers. A 6.9 or 7.3 is easy to work on. E4OD transmissions have a computer to control them. C6 does not but it doesn't have OD, so your MPGs are less. The manual trannies are pretty self explanatory, no computers. There are 4 speed and 5 speed models. 5 speed has OD and is preferred by many.

The years are 83-94.5 so yes, you can wind up with a 94 Power Stroke but you will notice that the engines are completely different as soon as you look at one. 93-94.5 had the option of a factory installed turbo. These are in high demand because they are rarer and the turbo adds power and MPG. It also adds one more piece that could fail.

I would say buy an IDI that fits your budget and has the features you need. I would not be overly worried about 6.9 vs 7.3. Both have good and bad points. Some will say the 6.9 is more reliable and less prone to cavitation but a properly maintained 7.3 will last just as long.

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  #3  
Old 08-23-2011, 11:36 AM
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Welcome

The above posting is true.

This is the later gp system.....
http://www.ford-trucks.com/forums/90...le-system.html

This is the old system.....
http://www.ford-trucks.com/forums/90...old-style.html
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  #4  
Old 08-23-2011, 12:15 PM
joe f350 joe f350 is offline
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the idi is a great motor either model. i lean to the 6.9 since the 7.3 is over bored and the motor can be prone to cavation. if the proper coolent isnt used in the motor. so it can be a gambel when buying one .
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  #5  
Old 08-23-2011, 12:36 PM
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Truly the single best year for the IH IDI engine is 1987 - 6.9L

Reasons:

- 7.3 style stronger rocker arms
- Solid state glow plug system
- 85.5-newer stronger block (no worries if using block heater) ((83-85 had thinner blocks at the block heater area and is at risk of cracking.))
- 6.9L, so no worries of Cavitation like on 7.3's (very highly recommend doing a search on this topic in this forum to get informed about this, truly important to know if your going to be a 7.3 owner, or even a 6.9, it's cheap insurance.)

Only con about the 6.9 in general is the smaller head bolts, and all 6.9's are more likely to have head gasket failure for that reason. The head gasket went on my 87 6.9 under 100k miles, and my 7.3 has 377k miles and all original, heads have never been off the block!


Now 88-94 7.3

Not many cons really, only 2 and one major one is Coolant additives, if no coolant additives were used in the cooling system, ever. They will last no more than 150k miles.

If proper coolant additives are used and checked regularly (I check it every oil change) they can last forever!

2nd con (minor one) is 7.3's have 2 coolant jackets plugged in the each head. Why did they plug them at the factory? No idea, but that's how it is.


6.9L has 170HP @ 3300RPM, 325ft. Torque @ 1600RPM.

7.3L has 180HP @ 3300RPM, 375ft. Torque @ 1600RPM.



But really, if you find a nice IDI that your personally love and is what your looking for, whatever year you get, let us know here on the forum, and we'll inform you on everything you'll need to know about it and what to maintain and keep an eye on etc., and how to make it last as long as possible!



And finally, welcome to the forum!
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1990 Ford F250 4x4, ZF5, L/S 4.10, N/A 7.3L Diesel, 568,808km/377,497 miles, still on the original clutch!
1989 Ford F150 300-6, C6, 2.73, 135,000km/84,000 miles.
1987 Ford E350 26ft. Motorhome, N/A 6.9L Diesel, C6, 3.54, 277,000km/173,000 miles.
1985 Ford E350 Ext Van, 6.9L Diesel, C6, 4.11, 670,000km/419k miles
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  #6  
Old 08-23-2011, 01:08 PM
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+1 on the above - excellent post and advice!! The cavitation issue is key.

The only thing that I would add is that one downside of the manual transmission is the dual-mass flywheel, which is much more expensive to replace than a gasoline-engined single-mass (or conventional) flywheel and clutch setup. You can replace the dual-mass with a single-mass flywheel but it causes some gear vibrations known as "rollover" which bothers some people. You can search on this topic and find lots of reading.

I was searching for a diesel from this vintage for years for the exact same reasons as you, finally giving up this spring and getting a really clean truck with a 460 gasser instead. The cavitation issue really scared me away. 99% of the sellers that I talked to didn't even know what I was talking about when I asked them about SCAs (supplemental coolant additives). I didn't want to pay $5K for a used truck and then have to spend another $5K putting a new engine in it a few months or years later.

If you can find one of these that was properly maintained (esp. if a one-owner), I'd get it quickly. The demand for these older diesels is still amazingly high (many people just don't want to deal with the super-complex and expensive-to-service newer ones) so when a good one hits the market it usually is gone in a couple of days, at least here in the PNW.

Good luck with your search, and update this thread (with pics) when you get one.
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  #7  
Old 08-23-2011, 01:12 PM
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If by any chance a find a 7.3 with less than ~140k miles (original mileage) and has NOT been maintained with SCA's. I personally would still go for it.

It's border line, but can be saved, now you have to know the damage done, will not be fixed, but can be stopped, as long as it's caught in time!
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1990 Ford F250 4x4, ZF5, L/S 4.10, N/A 7.3L Diesel, 568,808km/377,497 miles, still on the original clutch!
1989 Ford F150 300-6, C6, 2.73, 135,000km/84,000 miles.
1987 Ford E350 26ft. Motorhome, N/A 6.9L Diesel, C6, 3.54, 277,000km/173,000 miles.
1985 Ford E350 Ext Van, 6.9L Diesel, C6, 4.11, 670,000km/419k miles
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  #8  
Old 08-23-2011, 02:05 PM
poocher pup poocher pup is offline
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I liked the extra torque of the 7.3 but the 6.9 i have now with the t-19 4-speed pulls just as well, and i can't tell difference in mileage, 7.3 was e4od. As to drivetrain,automatic vs manual & 2 vs 4 wheel drive really depends on what you are going to use the truck for, where and how you drive, and how much you are willing to spend. Also do you need a kingcab or crewcab,pickup or flat bed, and maybe a dually.
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Old 08-26-2011, 10:13 AM
mylespowell mylespowell is offline
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Thank you very much

Thank you all very much. I appreciate all the knowledge you passed on to me. I am now looking, for a pickup, and I am sure I will be back to ask many more questions as I try to get to know it. Thank you everyone.
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  #10  
Old 12-01-2012, 06:40 PM
slvrwrx slvrwrx is offline
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Hey guys I've got an 88 7.3 IDI. I bought it running pure water in the radiator.. it had a banks turbocharger on it.. with the intake boot loose to unfiltered air.. and also had dryer vent hose used as air filter relocation.. but it flaked off and severe turbo wheel scarring and what one can only assume severely dusting the engine.. I fixed all these problems when I bought it and drove it for a year or so. It now has 147k miles.. won't run.

Long story short. I found an 87 IDI 6.9 83k miles andd I was thinking about buying It and putting it in my truck. What I've read here sounds like it's reasonable... and if I want to use my turbo I should stud the motor. Can anyone help me out with their opinion?
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Old 12-01-2012, 10:17 PM
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To the OP. I just purchased an '88 7.3 with 120K on it. It was well kept, but the owner had never heard of SCA's. First thing I did was add SCA. From everything I read the motors are good to 150K without and SCA, with it they will run 400-500K with just routine maintinance. Just expect that with this age of vehicle, you are going to have some things to address, even on a well maintained one.....so has a little $$ set aside for these things.

This is my first diesel, and so far I love it.
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  #12  
Old 01-21-2013, 08:28 AM
charger6t9r charger6t9r is offline
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I have owned my 94 idi turbo diesel for 4 years now. The previous owner was my fatherinlaw who bought it brand new. (she is know to many as big red) She is my pride and joy. I recently became familiar with cavitation which scares the he double hockey sticks out of me. my fatherinlaw was just as ignorant to the subject as me. currently there are no signs of cavitation. visually and mechanically that is. she has 156,000 miles and runs great. he always kept up on maintenance with the exception of sca's. NOW i run fleet coolant with additives. What are the chances my engine was damaged and if not, by running the proper coolant would that stop any further damage if any has been done. I know the for sure thing to do is a comp test but i am scared of the unknown. and if it aint broke dont fix it, just maintain it. Thanks everyone. any info and words of comfort are greatly appreciated.
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  #13  
Old 01-21-2013, 09:19 AM
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Quote:
Originally Posted by charger6t9r View Post
if it aint broke dont fix it, just maintain it. Thanks everyone. any info and words of comfort are greatly appreciated.
Click the image to open in full size.

If there is any damage it can't be undone. And there is no point in worrying about things that are not in our control.

Maintain it, drive it, forgetaboutit.
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Old 01-21-2013, 09:40 AM
charger6t9r charger6t9r is offline
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Thanks, maintain and drive. pretty sure everything is good but ,i am a worry wart by nature.appreciate the response.
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  #15  
Old 01-21-2013, 09:57 AM
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or just sleeve the whole block and never whorry bout it bout 1000 bucks bepending on your shop i guess i just sunk 2000k into my truck but now i have a motor with a turbo and 0 miles built my way over done but thats just me theses motors are by far best in my book ive go a 7.3 idi and ill never swing from it already ordering parts for my flat bed (next project 7.3 idi with ATS turbo ) lol 4x4 6.11 gears front rear with lockers
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Old 01-21-2013, 09:57 AM
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