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7.3 IdI -newbie info

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Hobbywelder, Jun 18, 2019.

  1. Hobbywelder

    Hobbywelder Registered User

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    folks, I hope everyone is well and ready for a go round of diesel info questions. Skip down a bit if you want straight into the questions.

    A little background on myself, I work in Collision repair and do personal mechanical things on the side, im an vet who resides in CO. I have a 1993 Ford F-250 with the 351w (we’ll get to that) and the Zf-5, with 4.10 rar, 168k miles. Im familiar with gas motors, but I also hate them. Unless its a race motor. I also hate automatic transmissions, and they are my most hated thing.

    So.... with the above stated, im looking to diesel swap my truck. The 351w, although not a bad motor, made 200hp and 300lbft of torque stock. The lightning model only added 40 on both ends. If I wanted to swap heads, intake, exhaust and do a full rebuild and change the cam I could maybe see up to 60-80 extra. Even the 7.3idi turbo, can beat 380lbft of torque.

    So, lets get to the nitty gritty.
    Maintenance wise, what do I need to know about the 7.3 Idi, maintenance costs, every detail. From what oil does it require to.....? How expensive is a rebuild minus block work?

    I heard something about checking the coolant annually, corrosion being the reason? Why is this and can it destroy a motor entirely? Finished FAQ reading. Know the answer, essentially yes. And its not cheap if it happens.

    Turbo’s, from the ‘92 model year up, is it better to buy one and build the kit for it or to buy a pre-fab kit? How much can these motors handle? If it’s possible, I’d like to see 200-220hp and 380+lbft of torque. I know that wouldn’t change what gear I’d need for going up hills but i’d make it easier than it is now. Lets rephrase that, Can this motor reasonably expect to 1: pull 4-6000lbs better than a 351(maybe 20 times a year) 2: handle 80mph turbo’d?

    Given I see a lot of these motors were mounted to an auto trans, what needs to be changed over for a manual? I know my Zf won’t fit, ill need a big block tranny from a 7.3 or 460 (I don’t think just the bell housings or whatever it is are removable and can be swapped) to mate to it. Ill already be changing the wiring harness and dash over but will the auto tranny things work or will I need to find other parts?

    Ive heard the IDI’s are a real bugger to start cold. Are they really any worse than any other diesel? What are my options for a remedy?


    I have a possible donor truck. Its a 1992 f-250, it runs. BUT it blows smoke, and not roll coal kind. Thats all the guy has listed. It has an auto tranny. What comes to mind with this?
    Could it be that coolant issue? Could the block be bad?

    He said make an offer, and personally I have no idea what its worth. I don’t want to overpay or lowball the guy if its a candidate for a rebuild. Considering someone else is selling a ‘95 psd for $900, unknown run and drive. I don’t want a psd because I know maintenance on them is drastically more expensive than the IDI or my 351.
     
    Last edited: Jun 18, 2019
  2. Hobbywelder

    Hobbywelder Registered User

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    Oh I forgot to mention:

    Speed limits on the highway here are 75mph. Will the IDI allow me to go that fast? Without a turbo? Or will it need a massive turbo to do that in 5th?

    Hauling 4-6k (I rarely break 5k) can I do 70mph?

    Since im in CO, I can go from 5000ishft to a little over 14k. How does the motor handle hills?
     
  3. Selahdoor

    Selahdoor Full Access Member

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    "Not the roll coal kind."

    If the smoke is blue, valves could be leaking past the seats.

    If the smoke is white, smell the smoke. If it smells sweet, it's coolant. You know what that probably means.

    If it smells acrid, it's probably unburned fuel, and the injection pump may need to be advanced or replaced.


    There are other possibilities but those are the most common.
     
  4. Golden Helmet

    Golden Helmet Full Access Member

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    I can't answer all your questions, but this one I got. If you're NA, these engines absolutely fall on their faces the moment they see a hill. The good part though is you can run the engine at redline all day long up the hill and it'll love you for it, but without a turbo you'll be really disappointed.

    A few others I can knock out, starting with maintenance. The coolant issue you read about is called "cavitation", and if you run coolant with the proper SCA's (Supplemental Coolant Additive) it's something you'll never have to worry about. Oil changes take 10 quarts, or 11 if you use the bigger filter from a 7.3 powerstroke. Keep spare belts handy because the serpentine tensioners give a lot of people grief, and on V-belt setups the alternator belt loves to go MIA and that takes out your power brakes.

    Beyond that, almost every old IDI is going to need new return lines / caps / o-rings. Changing the glow plugs is often a good idea too, just incase the previous owner put Autolites in there; if the PO tells you they just recently changed the glow plugs, that's a red flag because 99% of the time they put Autolites in there just to sell the truck.

    Lastly for maintenance, you should consider the cost of an injection pump + injectors and factor that in to your budget. If the engine runs fine as-is then you can run it 'till it blows, but a lot of these old trucks have tired old pumps and injectors that really need to be replaced. A new pump can really wake up these old engines.

    Regarding cold starts, these engines start extremely easy as long as everything is working half-decently. If you have air in the lines, non-functioning glow plugs, weak batteries, bad battery cables, or a weak starter, THEN the IDI becomes a bear to get started. None of that has anything to do with temperature, generally speaking IDI's don't care about the cold. Fuel gelling is a big issue when it gets cold, just run anti-gel additive in the winter, keep a bottle of Diesel 911 handy, and plug in the block heater if you're really worried. Here's a video to give you an idea, it's only cold by California standards but at the time my batteries were weak, my starter is still weak, and the truck started like it was nothing.

    That's about all I got for right now, I gotta sleep eventually. These engines are not fast, if you're looking for a diesel powerhouse you might want to consider something newer or a 12v Cummins swap. But IDI's are very simple beasts, easy to work on, parts are relatively cheap (one 7.3 Powerstroke injector costs more than 8 IDI injectors, for example), and they'll take a LOT of abuse. Worry more about the truck wrapped around the engine, because that's where most of the problems are on these 25+ year old tanks.
     
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  5. chillman88

    chillman88 Supporting Member Supporting Member

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    Power level depends on how much money you want to throw at it honestly.

    @typ4 (Russ) sells stock style turbo kits if memory serves me right.

    @Thewespaul (Classic Diesel Designs) and @Agnem (Conestoga Diesel) both offer turbo kits as well and I'm sure they can fill you in on the details if you ask.

    As far as 75mph empty yes, my NA truck will do 75-80 empty. I have 4.10 gears and she's screaming pretty good at those speeds but not complaining.

    Cold starts? Mine starts just fine all winter not plugged in. Make sure everything is in good shape and it won't give you trouble in the winter as long as you run antigel.

    These engines aren't fussy, but the difference between being "right" and "close enough" on timing can make a tremendous difference. If you are able to, plan a new injection pump and injectors from one of the vendors I listed earlier. It will ensure your engine runs it's best. If you've read the FAQs I'm sure I don't need to warn you about cheap injection pumps.
     
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  6. Hobbywelder

    Hobbywelder Registered User

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    Good to know gents. Thank you for the info.

    Considering what time it was last night, and some info provided let me rephrase a question:
    Hills, how do the turbo’d models handle? Seems like they’ll rev out all day, but will everything outside the motor handle it?
    As it stands with my stock 351, I can be doing 80 in 5th (2900rpm or so) and need to drop to 4th gear for anything more than a mild increase. If its a pass through the mountains, say 45mph speed limit. Ill need 3rd until it levels off. That doesn’t really change with 2000lbs behind me. Idk about 4k or more at this elevation.
    I used to live at just above sea level. 1500 in the bed with 5k in tow meant 3rd gear on tall hills and high RPMS but I’d make it doing 45.

    Think a turbocharged model could keep up or outpace current standards a little?
     
  7. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    My pickup
    My pickup(check signature) would tow circles around your 351 by the sounds of it, to give you an idea. A turbo wakes these engines up bigtime, and a stock IDI can handle up to 15psi just fine. A charge air cooler makes a big difference over just the turbo, well worth the effort.
    And a turbo maintains the volumetric efficiency of the engine at higher altitudes like N/A can only dream about! You will still lose power when you gain that much elevation, but it will be far less than N/A.
     
  8. Hobbywelder

    Hobbywelder Registered User

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    For whatever reason I can’t see anybody’s sig line.



    They guy got back to me, he said the truck has a stock turbo. Which means its either a ‘94 m/y engine, or its been robbed from one that had a turbo.

    He also said it billows white smoke. But he thinks its the turbo because it fills up the engine compartment.

    F1307657-9724-4453-B8A2-546038570F95.png
     
  9. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Being at your elevation at your elevation, you are really going to be happy with the power increase a turbo would give you. With a decent condition fuel system and a healthy turbo you can more than double your current power. Ive got a complete turbo kit for sale for $850 that has every nut and bolt to make the conversion. I can machine the turbo for larger wheels too for a reduced cost as well if you want to have it done before you install it.
     
  10. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    This is your best bet for the money by far. I got a complete kit for $800 on Ebay and had to turn around and pay $650 for a new CHRA plus all the time and frustration and disappointment that goes with a poorly running turbo you have to install twice.
     
  11. Hobbywelder

    Hobbywelder Registered User

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    Well the idi I was looking at is toast, the smoke is so white you’d swear it had a feeder with baking powder in it.

    Found another, maybe that will pan out...
     
  12. nostrokes

    nostrokes Full Access Member

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    Here we go from a fellow Coloradoan, almost Wyoming!!

    Maintenance will of course be more expensive. More oil, more expensive filters ECT... My oil change that I do myself is roughly $80-$90, compared to $40 for the wife's explorer. 15w-40 oil is what I run year round. There are recommendations to swap to a lighter weight in the winter, but I'm not going to change. As stated before, belts like to walk, return lines and caps are always needed (but fairly cheap), and spare parts on hand are always good. I also run Dieselkleen additive in the fuel at all times. White bottle is for winter, it has anti gel and lube in it. I just use it year round. Have to have the lube, the new diesel is "dry" and doesn't lube the fuel system like the old diesel did. Any replacement parts you should try to get motorcraft, thermostats, glow plugs (always!! no autolite crap).

    Coolant isn't as bad as people think. Also lots of threads here about that. Biggest thing is sca's like said before. You also have to make sure the test strips match the sca you use. NAPA strips will not work with Ford SCA fluid and vise versa.

    Being here turbo, turbo, turbo. Mine is a 91 ext cab, 4wd auto. It's got a banks sidewinder non waste gated. I've heard the non waste gated is better for towing because it holds the boost instead of dumping it at the top end, but I'm sure there are arguments both ways. I didn't have a choice, that's what was there when I got it and I don't plan on doing anything different. I haven't pulled more than 6k with it, but I hardly noticed it was there, uphill, down hill, didn't matter. Unloaded it isn't a speed demon, but it will get up and go better than expected. Haven't taken it over a 14ner, but the hills in the mountains where I'm at haven't been bad, not as good as my bored out 460, but not bad. I drove many NA's and they were really snails everywhere you went.

    Adapting a auto to manual: lots of threads here on that subject. Basically find a doner truck and take every last part you can from it. It's easier and cheaper that way. An auto wiring harness will work, but you have to fake out the mlps, and not sure about the reverse lights and such.

    Cold starts, I don't have an issue. I keep it plugged in all the time when its below 15*, plug it in for a couple hours above that, don't usually plug it in if it's over 50-55*. I only have 3-4 glow plugs that work, but if it stays above 55* I don't usually need them if it sits overnight after being run. I work nights and they have outlets for us oil burners so right now I just plug it up, but don't really need to. As long as you keep the fuel system clean and air tight , and have a good starter and batteries it's usually fine.

    These can handle good amounts of boost if they are done right. Thewespaul has done lots of mods and has a good handle on the breaking points, so he and others here are a great reference for that.
     
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