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Swapping a 5.8 for a 7.3

 
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Old 08-17-2009, 08:16 AM
boggerted
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Swapping a 5.8 for a 7.3

I have always wanted a diesel in my truck, so I found a local guy with a F250 2x4 with a 7.3 idi and a zf 5 trans. I want to swap out the 5.8 that is in my truck for the 7.3. Does this make sense? Will the 7.3 make more power than my 5.8? thanks
 
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Old 08-17-2009, 08:49 AM
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Originally Posted by boggerted View Post
Will the 7.3 make more power than my 5.8? thanks
In stock form the IDI makes a bit more low rpm TQ than the 5.8 but it makes less HP and there's nothing you can do to improve that while the 5.8 can be easily upgraded to deliver lots more HP and TQ.
 
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Old 08-17-2009, 09:07 AM
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IMO if you want a diesel go to the 7.3L powerstroke. not the idi. about all you can do to the idi's is turn up the fuel screw, but that will get you minimal power gains. the powerstroke you can do a chip, injectors, turbo, full build to 1000 hp... what ever you may wanna do. the 5.8 can make much more power than the 7.3 idi
 
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Old 08-17-2009, 09:57 AM
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You can always turbo an IDI which nets more power but you will still be well behind the power of a powerstroke and a bit above a 5.8. Plus my buddy who turbo'd his 6.9 said that the clearances are very tight to work with.
 
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Old 08-17-2009, 11:41 AM
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How would the fuel economy be? Right now I barely get 12 mpg aqnd I would love to do better than that.
 
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Old 08-17-2009, 01:43 PM
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Well after some googling I find that most people with 7.3L IDI's seem to push between 15mpg and 19mpg unloaded and at 65mph. With most averaging at 17mpg and 10-12 pulling a 10k trailer. This all depends moreso on the rear gears and tranny.
 
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Old 08-17-2009, 02:23 PM
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Yes the early non turbo diesels delivered outstanding milage, the best was the original 5.9 Cummins.. mid to high 20's was common when unloaded.
 
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Old 08-17-2009, 07:05 PM
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it will just be a gutless noisy dog... better wait it out for the powerstroke or it wont be worth it.
 
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Old 08-17-2009, 10:12 PM
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Well I already know where I can get a ford factory turbo fromn a 94 turbo idi so that should help. I dont plan on winning any races, I would much rather have torque for hauling and better fuel mileage. Also, is there anything different internally on a 94 turbo idi block that would prohibit me from putting that turbo on this idi?
 
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Old 08-18-2009, 12:10 AM
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well it sounds like you got your mind made up. with the turbo you will probably be happy so go for it. i dont recall any difference but i am not sure
 
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Old 08-18-2009, 12:14 AM
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well this is a tough question. i would not swap in a PSD due to the electronics reguired for the retrofit. the IDI is a straight forward swap. yes it is low on HP, but it will work all day long just like a PSD. people are fascinated with big numbers, but at what cost? for the price of some upgrades to a PSD u can buy a turbo for the IDI, fab an intercooler and buy a moose or any other hot turbo pump and still be ahead knowing that some basic hand tools and common knowledge can repair ur truck. most of everything is easily accessible N/A and not to much worse turbo (definatly no worse than a PSD).

right now im running an IDI 7.3 in my 88 F-350 N/A and it does what i want fine. id like a more HP to keep my speed up on the long hills but i just drop a gear and let it rev, the IDIs like to rev. i ran mine at full govener for quite some time pulling some big hills in 4th (unloaded) and it actually seemed like it was happy at 3800 RPM lol.
 
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Old 08-18-2009, 07:47 AM
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The ford turbo is a waste of time unless you put ATS' housing on it. The ford turbo only gave 10 hp more than a N/A engine
 
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Old 08-18-2009, 12:48 PM
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Originally Posted by nat13_3 View Post
Well after some googling I find that most people with 7.3L IDI's seem to push between 15mpg and 19mpg unloaded and at 65mph. With most averaging at 17mpg and 10-12 pulling a 10k trailer.
With a cam and longtube headers my 5.8 f150 was getting 17+mpg at 70mpg unloaded and that's with an auto trans so a manual should do even better. The motor was producing about 380ft/lbx TQ and maybe 275hp which puts it well above the IDI on all counts, and the TQ came in real low.. no problem spinning tires on dry pavement just by punching it from a stop. Considering you can get that for literally a few hundred dollars in parts it's hardly worth the effort to swap in an IDI IMO.
 
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Old 08-20-2009, 05:05 AM
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most ppl that i have heard of putting the ATS upgrade turbo on the 6.9's say it's the biggest waste of money. don't think its worth the couple grand when you notice you still have no power. haha. the 7.3 factory turbo idi was a little better than the 6.9, but the ones i have driven were just dogs. idk if they got good mileage but i know they don't feel like they wanna pull themselves, much less a fully loaded trailer behind 'em. my stroke gets 21mpg hwy with 160cc injectors, custom tuning, intake, exhaust, etc. it's all in my sig. haha. i have plenty of power to pull with and with the intercooler i put in from a '00 super duty it doesn't get hot too terribly fast anymore either.

the 5.8 may not get quite the mileage a diesel does, but i don't think your going to like driving that 7.3 idi. i think the 5.8 may have came stock with more hp than the idi did too. idi's didn't even come with 200hp..
 
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Old 08-21-2009, 09:20 AM
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As much as I do like the older 7.3's, if I was to do a diesel swap like your talking about, it would be to a cummins 5.9. You can boost the power up on them for pretty cheap, and you will have all kinds of power, and mileage.

If these are your only two options, the diesel will provide the lugging power that diesels are known for, with great economy (if you want to make your truck a good puller)

If your looking for just power and mileage isnt as much of a concern then it sounds like a 351 would be the way to go.

For what its worth, my dad has a 91 f250 supercab longbox with a 7.3 idi, 5 speed manual, and 4:10 gears. It has an aftermarket cts turbo on it. No shortage of pulling power.
When he drove it regularily, he was getting 25 mpg (canadian) empty, or loaded right up.
He actually likes that truck better then his 01 diesel, for the comfort, etc.
 

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