Rebuild the IDI, or swap in a Cummins

[memphisrain]

Hi all! I've been lurking for a long time and it is about time I start restoring my truck. However, I'm at a crossroads with regards to the motor and I would like some input from you guys that are obviously far more familiar with these engines than I. I apologize in advance for the rather long post, but I appreciate your input.

Here is the story:

As my sig says, I've got an '88 with a 7.3. I bought it used with 175,000 on it when Diesel was $0.99 a gallon (~9 yrs ago). I'm convinced now, after doing a fair amount of research, that the thing has never really run to its full potential. I have always had problems getting it to start without cranking for a long time when the temp was below 50 degrees or so. I have replaced the injection pump, glow plugs, and control module on it. It started better after these fixes, but still never really right. Having said all of that though, it has never ceased to be dead reliable for me and has always got me home.

At this point in time, I'm getting ready to restore the thing, because it has a lot of sentimental value due to it being my first vehicle and it has always been reliable. At this point, I know the motor needs injectors, IP, new glow plugs, and the heads need redone, due to blow by from what I've read is bad valve guides. When I get the heads off, I'll take a look at the cylinders to see what they look like, it may need a complete rebuild.

My goals for this truck is to get to start reliably, and increase hp on it. I eventually want to use this truck to go out west to pick up old cars and build hotrods out of them. So I envision eventually getting a trailer that I can haul two or three cars on at a time. I want the truck to be able to to run 70-75mph comfortably, and still have enough pass quickly (ie. I don't need a five mile run at it). Obviously the truck will be used for other things as well, but that is the max stress that I envision myself putting on it.


Here is where I would like your guys' input: Will an IDI with a turbo do this? I'm really unsure of what they are capable of, because I don't think mine has ever run completely right. I'm also trying to weigh the costs. I figure I'll have around a grand in just rebuilding the heads, a new IP, new injectors, and glow plugs. Then somewhere around 2 grand in a turbo kit. All of this is assuming the lower end is o.k. I can get a used Cummins for $1500 and the adapter and motor mounts for another grand and I can get around 300hp for very little money (from what I've read online) I'll be doing all of my own work, other than the machining, so labor costs don't really factor in. Am I off base on my costs? Is it risky putting a turbo on an engine with as many miles as mine has?

Please try and keep the whole brand loyalty thing out of this, as I'm just trying to find the most economical way to build this truck to meet my needs. Any and all input otherwise is appreciated.

Thanks for reading all of my ramblings,
mR

 

[69dieselfreak]

if you have the moeny id have to say a cumapart with the p-pump
i dont care what people say but a ford with a cummins is the best allaround truck out there that just my opinion of cource

 

[Diesel JD]

What's for sure is that you can definitely get serious power out of the Cummins and those who have swapped one in have been really happy with it. With a turbo IDI you can reliably make 200-250 HP and LOTS of torque without extensive mods. If you want to keep the IDI and go for big HP you'll need an intercooler, a set of head studs and a hot DB2 pump. Shaving the pistons a bit and then ceramic coating gives you a bit more of a fudge factor. Also you can save some coin by cobbling together your own turbo kit or buying and restoring a used IDI turbo kit. One member here is using IH T444E or Dt466 turbos on IDIs. Seems like if you are up to building hot rods and doing all this work yourself you have the skills to do this. For the best fuel economy and easiest high HP though I hate to say it but the 12V Cummins, a set of bigger injectors and a few other mods would be the way to go.

 

[towcat]

Here's my .02....now keep in mind I have all three makes.
IF you have 10k kicking around for a conversion, do the conversion. If you're on a budget rebuild a IH idi and stuff it in your chassis. The IH is trully a blend between the economy of the Chev and the stump pulling power of the Cummins. Unfortunately no single choice comes without a price and that is what you will need to evaluate if you can live with it or not. I do have a Cummins conversion in the works, but it's not going into one of my front line trucks. There is going to be much experimentation and fitting going on, therefore I can't take a frontline truck needed to make a living with out of service for long. Also, the cost of the project isn't going to be cheap even though I got the chassis for a reasonable price. You're the only one who knows your situation the best, only you can answer the question of cost, time, and technical ability better than anyone else can.
Oh yea, there was a time before Sandbox II where military surplus GM idi were cheap, but not so anymore. That makes the IH idi the king for inexpensive in a matter of speaking. That's why most of my trucks are IH idi's.

 

[69dieselfreak]

wonder why the gm idi went up in price so much

 

[LCAM-01XA]

wonder why the gm idi went up in price so much

Cause if the chevy gets about 20 mpg then something ain't right with engine - them things are well known to hover around 25 mpg if you drive 'em easy.

Of course the putting power ain't really there, but if you don't tow that ain't much of an issue

 

[towcat]

wonder why the gm idi went up in price so much

GM idi's were cheap due to a overabundance of military surplus. That all ended when Sandbox II hit. Now the only surplus GM idi's you see are the blown up junk being pulled out of the humvees. Although when the whole deal finishes off over there, there's going to be some screaming deals on the 6.5 motors with the oil cooling jets
just as an example.....
there was a time when I could repower a GM C30 towtruck with a surplus motors bought for $50. Now how could you not like a GM idi?

 

[RLDSL]

Before condemning the engine, you really ought to try eliminating a few variables first to see if it really needs rebuilding/replacing.
If it's always had trouble starting, good chance the pump timing is off ( retarded ).Did you have it timed after the pump replacement, or did you line up the marks? you should put an approximate location in your signature, you may be near someone who could help with timing etc If the injectors are original, they are WAY overdue for replacement
Blowby in an old diesel doesn't have to mean anything bad. In many cases it's just sticky rings gunked up with lots of soot and varnish. Your compression could be a couple of hundred PSI below it's potential just for lack of a good cleaning ( which would give you blowby, and make it hard to start )
A couple of treatments of Auto Rx can do wonders. I've revived a number of old diesels from near death with that stuff.

 

[memphisrain]

Thanks guys for your help so far, a lot of good comments that have got me thinking.

First, no one has answered my original question. Will a Turbo IDI to what I want to do with it (three car trailer, 75 mph, passing, blah, blah)?

Second, I'm not really interested in using this particular truck to make big hp numbers. I just want to be able to two across the country reliably, and have enough hp/torque to run at modern highway traffic speeds.
Third, 10 grand for a Cummins swap? Am I missing something? I figure $2500-$3000 for the motor, adapter, and motor mounts, and may be another $1000 for all of the miscellaneous stuff. I'm not sure about what I'd do with the other $6000.

Fourth, I'm in no way condemning this engine. I know that it needs head work along with injectors, pump, and glow plugs. I just don't know what the bottom end looks like. I'm just wanting to know what the IDI will do when it is running properly with a turbo.

I'll check into the Auto Rx RLDSL, thanks for the tip.

Like I said, I'm pretty sure, this truck hasn't run properly since I bought it. I'm kind of surprised about how little I knew of this engine and its maintenance requirements. Finally, I found a use for this internet thing besides ****!


Thanks again,
mR

 

[6 Nebraska IDIs]

Here's my opinion, and I can say it because I have both types of the IDI engines.
A turbo'd IDI is a COMPLETELY different animal than a N/A one. But BOTH are dogs when they arent timed correctly.
When hauling our 2 car trailer loaded we had to keep an eye on the exhaust temp going up long inclines, and had to slow down a couple times.
Yes these will run modern hwy speeds 70-75, but at little economy. The turbo's help these engines an astronomical amount. But they wont have the power a cummins will offer.
If you can start from a clean slate with one of these engines, they will literally run forever if you take good care of them.

 

[memphisrain]

What's for sure is that you can definitely get serious power out of the Cummins and those who have swapped one in have been really happy with it. With a turbo IDI you can reliably make 200-250 HP and LOTS of torque without extensive mods. If you want to keep the IDI and go for big HP you'll need an intercooler, a set of head studs and a hot DB2 pump. Shaving the pistons a bit and then ceramic coating gives you a bit more of a fudge factor. Also you can save some coin by cobbling together your own turbo kit or buying and restoring a used IDI turbo kit. One member here is using IH T444E or Dt466 turbos on IDIs. Seems like if you are up to building hot rods and doing all this work yourself you have the skills to do this. For the best fuel economy and easiest high HP though I hate to say it but the 12V Cummins, a set of bigger injectors and a few other mods would be the way to go.

I definitely dig fabricating my own stuff, for money savings as well as pride. Is there any good info around the net on these turbos? I was also considering using a PS turbo, but I don't know if it would make too much boost.

Here's my opinion, and I can say it because I have both types of the IDI engines.
A turbo'd IDI is a COMPLETELY different animal than a N/A one. But BOTH are dogs when they arent timed correctly.
When hauling our 2 car trailer loaded we had to keep an eye on the exhaust temp going up long inclines, and had to slow down a couple times.
Yes these will run modern hwy speeds 70-75, but at little economy. The turbo's help these engines an astronomical amount. But they wont have the power a cummins will offer.
If you can start from a clean slate with one of these engines, they will literally run forever if you take good care of them.

Is there some good information on timing the IDI. I'll do a search, but if there is a definitive article, I'd appreciate a link.

mR

 

[hesutton]

My $0.02 from reading the above, rebuild your IDI and add a turbo. The coversion seems to be pricer, plus, if I was going to repower one of these trucks.......I'd do it with a DT466. Not easy like a 5.9, but it's still an IH, and it is truely a rare coversion.

Heath

 

[Exekiel69]

The IDI is reliable and so the cummins I hear will see since I'm yet to finish My conversion. The IDI isn't going to drive 70-75mph with 2-3 cars in tow unless You go down hill You can push it but if You do it won't be as reliable anymore. The cummins 2gen (the one with the inline pump p-7100 94-98 trucks) will pull at 70-75mph but then again there is a limit to everything and when You go up a long grade You don't want to burn up things before You make it to the top.

Now for fuel economy the first gen ctd (89-93) are very good and will have more power than an IDI.

 

[DeepRoots]

hell if I had my choice i'd stick a 6v71 in my truck. These stinkin 4strokes are just big air pumps anyway.

seriously a turbo IDI with a good fuel system is VERY driveable at highway speeds. While towing you may or may not be pleased with it in the same situation. Guess it's what your used to, probably why I also refuse to drive in new trucks..... I'd end up dissatisfied with mine.

drew

 

[Cat_Rebel]

If your main goal is to turn it into a car hauler & tow alot with it & you don't mind the work there is nothing wrong with a 12v swap. Either a 89-93 with the VE pump or the 94-98 with the P pump. I say what ever you can get the cheapest, don't count the old 89-93s out because they aren't P pumped. The old dogs can still crank up to around 400hp with the VE pump & other supporting mods.