Recently, I received a question from IDI Online user “tanner” about the potential of conducting a gasser-IDI swap. I get this question a lot, and I usually go over the quick major points. I think it’s finally time I make a formal article detailing the potential problems, solutions, and advice for taking the plunge.
Here is tanner’s comment:
- “First of all, awesome site! Creating something like it takes alot of time and dedication, so. I commend you.
If you don’t mind answering a quick question of mine, it would be much appreciated, as you know information on vans isn’t easy to find.
I’m in the process of a buying a really nice shape 88 E-250 Camper Van with low oil pressure 5.8 liter, and figured that it would be a perfect opportunity to put in and IDI. From what I’ve read a non turbo version can be installed with few modifications. However, I found a 1994 7.3 IDI turbo truck engine for cheap and thought maybe I could modify it to fit. I just wanted your opinion on if this is at all feasible?
I wrote a brief response to get him started. This basically helped him with the broad strokes regarding the required diesel components and the differences in the IDI truck and IDI van engines.
Installing an IDI engine in a van is no short order. Combine that with the indirect impact of the swap in the van and it’s a major undertaking. There are many things to consider: Wiring, Engine Mounts, Suspension Upgrades, Fuel System Mods, Instrument/Dash Panel, Exhaust Replacement, Accessories, Battery Installation, Vacuum System, Transmission Bell Housing, Driveshaft, and a lot more.
Is the swap worth the effort?
I personally think doing a Gasser-IDI swap is way too much work, money, and time. The best course of action is to buy an IDI Van or IDI truck from the start. They are not that rare, and with enough searching on Ebay, Craigslist, classifieds, and Autotrader, you will find a viable diesel vehicle. However, there are some rare cases where doing the swap might be worth it:
- Camper Vans. RV’s, campers, and other unique mobile “homes” are not easy to find nowadays. If you own a special van with a bathroom, kitchenette, and other cool features, then a diesel swap might be a decent investment.
- Specialty Utility Trucks. Some contractors have modified their trucks and vans for their businesses. I’ve heard of plumbers, welders, and other tradesmen installing special tools, hydraulics, and functionality that wouldn’t be common in the typical IDI on Craigslist
- Refrigerated Vans. Some work vans had top-mounted condenser units to refrigerate the rear of the cab. While it might be easier just to move the air conditioning unit to an already converted IDI, this could be a moderate exception to the rule.
- Quadravan Conversions. Probably the only thing worse than the gasser-to-IDI project is the 2wd-to-4wd van conversion. There were companies that would convert 80’s vans “back in the day,” but that’s not common anymore. So, finding a four-wheel-drive van is already pretty rare, thus the prospect of tossing in an IDI might be worth the effort.
- Manual Transmission Econoline. I’m kind of an IDI Van expert, and I’ve never seen a manual 80’s Ford van in person. I know they exist, because a few have popped up on the internet. The owners say the clutch is really tight, because there isn’t a lot of room for four pedals between the door and doghouse. Regardless, since they are rare, it might be prudent to swap the gasser out, but then you’ll have problems finding the proper linkage and bell housing and transmission to accommodate the larger IDI.
That being said, if your goal is to take your standard Econoline with a 302 and put in an IDI, I’d highly recommend NOT doing that. There are still plenty of good quality IDI vans for sale every day. Instead of swapping the engines, sell your gasser van, and use the money to buy an existing IDI. It will be thousands of dollars cheaper than doing the swap.
If my preamble didn’t deter you, and you are still determined to move forward with the gasser swap, here are my notes:
Pulling the Gasser:
From 1975-1993, Ford installed a variety of gasoline engines. They had two small block engines (302 and 351) and two straight-six blocks (240 and 300). The only gasser engine that even comes close to the size and weight of the IDI diesel was the gasoline big-block 460. That means the vast majority of Econoline vans had a light-weight engine. This is something to remember for the rest of the article.
The 7.3 IDI engine is heavy. The beast is 920 lbs dry. Add in the weight of fluids and accessories and you are talking about over a half-ton of mass sitting on the front suspension. Contrast that to a fully dressed 302, and the small block weighs only 460 pounds. This means beefing up the front coils and shocks, at the very least. If you put an IDI in a typical small-block Ford van without upgrading the suspension, it will BOTTOM OUT the coils. Also, it would be prudent to improve to larger diameter tie rods, center link, stabilizer links, and anti-sway bars. I’ll have an article soon showcasing my recent front suspension upgrades.
The most important suspension improvement when swapping a small block to large block like the IDI, is replacing the coils and front shocks. I reviewed the various coils on the market, and most could not support a 7.3 at all. I ended up going with the MOOG CC860S Variable Rate coils because my stock coils could barely support my IDI anymore. They were rated for a few hundred more pounds than stock, so it gave me a little room for the i-beams to flex. If the vehicle has some unconventional modifications (like camper accessories) increasing the weight of the front end, there is an aftermarket coil rated for 1000 lbs over stock, which would be the highest possible upgrade. I splurged for Bilstein HD shocks as well, which help to accommodate for the increased weight of the IDI over the typical gasser engine. A cheap set of Monroes would likely fall apart after a few thousand miles, so buying quality is paramount.
For vans that have the front axle, I believe most have front leaf springs, which should be improved as well.
Fuel System Replacement:
The IDI has a rather convoluted fuel delivery system. It has several differences from the stock gasoline circuit. If you think you can just pour in some diesel into the tanks and hook up the lift pump, you will be rather disappointed.
The gasoline tanks have fuel pickups that have platforms for an in-tank fuel pump. This cannot be used for the Diesel fuel system. However, if one deletes the in-tank gasoline fuel pump, then the pickup could in theory be converted over to Diesel. Also, the Ford fuel pickup has a sender that corresponds to a specific resistance at a specific fuel level. So, the resistance transmitted to the instrument panel MUST match the stock gauge calibration, which is different between gassers and diesels, and trucks and van. I have a rather lengthy article detailing the conversion of a 460 gasoline fuel pickup for the Diesel van:
The stock fuel lines and selector valve may not be compatible with Diesel either. IDI’s have an assortment of metal fuel lines that begin on the frame rail and ride the crossmember to affix to the lift pump. Then the fuel lines clip to the front of the engine block and connect to the fuel filter head atop the engine. The camshaft drives the mechanical IDI lift pump, thus providing enough sucking pressure to eliminate the need for an electrical in-tank pump, like the gassers implemented. I have deleted my lift pump in favor of a Duralift E-pump, but the principle is the same: Using the gasoline in-tank fuel pump and fuel lines won’t work for Diesel.
The nice thing is, it isn’t that difficult to run new Diesel-rated fuel hose and connect to the lift pump or Duralift E-pump. In fact, this might be a great opportunity to replace the stock IDI filter head in favor for a set of R&D’s Stage 1 frame-mounted dual filters.
Electrical Harness and Instrument Panel:
As I mentioned in the aforementioned Fuel System section, some of the gauges and indicators are different from the gasser to Diesel. Unless you are willing to assemble your own gauge panel, you will need the entire dash console and accessories if you want the thing to operate like an off-the-showroom-floor IDI van.
The most important differences are the following: Fuel Gauge, WTS (Wait to Start) Light panel, and Tachometer. If you are not familiar with Diesels, they require a “warm up” period prior to ignition. When firing up the vehicle, the driver turns the key to “ON,” watches the WTS light, and once it turns off, the driver can turn the key to “START.” That turns over the engine after a set of glowplugs have warmed the pre-chambers to a requisite temperature. No gasoline powered vans would have this display, and waiting for the glowplug controller to do its thing is crucial to waking up these beasts.
The WTS light is also accompanied by two other safety lights pertaining to water in fuel issues or fuel pressure problems. These lights are triggered by sensors in the filter head and the other gauges receive signals from temp, tach, and pressure sensors on the block or heads. These sensors are wired up in a bundle (along with the glowplug wiring and grounds) called the IDI wiring harness, which would need to be married to the engine and replace the stock gasser wiring assembly. By bringing over the entire Diesel Ford instrument panel, fuse panel, and wiring harness, it ensures that the block will be installed in the former gasser engine bay without having a major safety crisis.
Radiator and Tranny Lines:
The IDI requires a massive and expensive radiator. Using the gasser radiator might work in a pinch, but proper big block engine cooling requires a monstrous coolant system. Failure to do this will result in long term block damage.
Along with a new radiator, then new tranny lines will need to be purchased or bent. Depending on the planned-usage of the van after the IDI swap, an auxiliary tranny cooler might be a good idea.
The existing gasser transmission won’t work for your IDI block. The bell housing on that small block won’t work, even if you have a C6 or E4OD tranny. Thankfully, the IDI transmission mounting adapter (Part #1800475C1, image to the right) will work between the C6, E4OD, and ZF (assuming your IDI has the rare manual option), so you won’t have to source that part. However, for all the small block and straight-six block engines, this won’t support the smaller tranny bellhousing. Even if you are fortunate to have the big block 460 prior to conducting the IDI swap (which is the closest gasser to the IDI), you have to drill out the unit to prep it for the IDI adapter.
Naturally, with any transmission modifications, the accessories will need to be swapped as well. The torque converter and driveshaft would require replacement. I upgraded to a Hughes HD TC so I could get better efficiency and better towing. Also, considering that not all trannies are identical, you might want to remeasure your driveshaft to make sure it fits into the new transmission tailshaft housing.
Swapping the Engine:
The 7.3 or 6.9 engine swap is like giving birth to a watermelon. I have four articles on this website detailing the birth pains. Here’s just one of them:
Pulling a 6.9 (or 7.3) IDI Engine from a 1988 Ford E250 Econoline Van
Modifying the Gasser Exhaust:
It would not be prudent to hook up an IDI to stock gasoline exhaust. The 6.9 or 7.3 IDI does not require a catalytic converter, so many NA systems just have a standard muffler. To reduce EGT’s, some people will run a straight-through high-flow exhaust system, with large diameter exhaust pipes. This would be most efficacious in IDI systems implementing a turbo kit.
Vacuum System And Other Accessories:
Diesels don’t produce vacuum like gas engines do. Instead, IDI trucks and IDI vans (along with the Powerstrokes) have a belt-driven vacuum pump, which provides vacuum for the vehicle’s brake power-assist system, the climate control system, cruise control adjustment, and shift control (for the C6 transmission). While the vac pump is located on the passenger-side of the engine, the “vacuum hub” is located on the front top of the engine bay, containing a tree of vacuum bibs for various accessories. The vacuum system ends with a sensor switch (located under the driver side battery tray) that turns on the “BRAKE” light on the instrument panel if the vac ever approaches atmosphere. Also, the system employs a silly looking coffee-can in the passenger-side fender, which acts as vacuum storage in cases were a spike in vacuum is consumed by the vehicle. Like if you shifted the transmission, turned on the air-conditioning, and came to a hard stop simultaneously. That vacuum system would need to be completely brought over from the donor vehicle to make this work, as well as the instrument panel, so the vac pressure warning light functions as design.
Batteries and Cables:
IDI’s require two massive batteries to obtain the requisite amperage to turn over that starter and flexplate. Along with two batteries, there is a labyrinthine set of wide-gauge cables that spread across the engine bay. Using the gasser battery cables won’t work. You need a way to put those massive cranking batteries in parallel to double the amps of the cranking setup. With the glowplug and the starter drain on the electrical system, the IDI cables are a necessity.
Also, the diesel has a fender-mounted solenoid relay to transmit that current to the starter. Make sure to pick up one of those to complete the whole electrical system.
Like I said before, it would be much easier to just buy an IDI van, rather than convert a gasser to a diesel. But if you are a stubborn guy like me, then feel free to give it a shot. I hope my notes have given you a decent headstart.
If I’ve forgotten anything, please comment below. I can augment the article to reflect your suggestions.
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