In the last episode of Operation: IDIocracy, our heroes were on the brink of defeat by the forces of subtle year-to-year manufacturing changes that aren’t really discernable at a glance.
For one reason or another, the driver’s side of the engine cross-member was too high, causing the engine to sit off-kilter and hit the passenger side of the compartment. To proceed further, I had to redesign the mounting bracket on that side to accommodate. Here’s how that whole quest happened!
I removed the driver’s side engine mounting bracket again so I could pivot the engine from the passenger’s side one using the crane to hold it. The error source seems to be entirely here: Raising the passenger’s side to level it out will put it too high up in the compartment and still too close to the wall. I had to lower this side instead.
It seemed like the raised, stamped metal bracket had to become a flat plate with the same hole pattern. This is a standoff distance of about 1/2″.
Here’s the overview of the arrangement showing the use of the Attitude Control Ratchet Strap purely as a sling. I had the passenger side mount only somewhat tightened down, so I could see if the motion was going to cause any undue deformation on the rubber core. Too much initial twist and engine mount life could be negatively affected.
I stuffed a bunch of spare metal cast-offs from the shop into the gap on the driver’s side so I could see what the whole thing looks like once it bears weight. The items shown are cuts from 30haul’s Shiny Metal Ass and some 1/4″ steel strips, with the total height being 5/8″.
So I started getting the impression looking at it from underneath that the mounting studs coming off the engine should be centered in these big holes in the cross-member. That entailed a standoff distance of 3/4″, which looked correct. If this is in fact the case, then for some reason in 1986 the mounts for the 6.9 IDI (which would have been correct for that year) must have been 3/4″ shorter or more.
Yet I couldn’t quite see where Spool Bus (a 1984 6.9) was different in this regard. Maybe one day if I have to take it apart in depth, I can go find out.
So where do I go from here? It was time to reverse-engineer the engine mounting bracket. I’m going to duplicate the essential mounting holes but compress the raised stamping into a single plate. Since it’s a 2D part, I just took a really long-zoom picture of it.
Simple as that. The long zoom flattens out the perspective – not entirely, but better than being up close. I imported the the picture into Inventor and just started drawing a part using my scale reference.
The two mounting holes on the right and lower edge were reused directly. The third mounting hole is one that fit the 460 bracket but which the IDI bracket does not use. I replicated the teardrop slots for the engine mount studs.
Here’s the solid part! I had one of the Enders print out a few layers of it as a validation of the hole pattern.
Looks like I was off by some amount. Nothing a quick eyeball-caliper measurement and some marker can’t fix.
Using the original sketch elements now as reference-only geometry, I made new features that were the measured offsets from the fit test.
The fitment was amazing! So all it took was one revision. All bolts threaded in by hand with how spot on the centers were.
And the engine rested with all of its weight on the mount basically dead center in these access holes.
There’s one slight change that I think is fine. Because the original studs were supposed to be bolted through about 1/4″ thick stamped sheet, and I’m putting them through a 3/4″ thick plate, there’s no more “stickout” of the stud. The nuts actually tighten on completely flush with the end of the stud. All of these coincidences made me believe I had reverse-engineered the actual geometric difference between the two cross-member versions.
Here is what things look like from afar. The engine sits level and there is still the tiniest quantum of clearance to the passenger side of the engine tunnel, but it was much closer to the “Every part of a Ford Econoline is 0.25 inch away from every other part” guideline.
I sent the flat cut file of the new bracket to OSHCut to be made in 3/4″ thick regular vanilla steel.
Not going to lie, I kind of wanted to find out if a Markforged print could actually work as an engine mount… Given the loading is mostly compression from the weight of the thing, and in-plane shear from torque, I feel like a fiberglass-backed Onyx print may very well have worked. But maybe I will try that for a vehicle with an easier-to-access engine mount.
In 10 minutes, the plastic prototype mount was replaced. Up the engine goes, the bolts come out, and the metal part is substituted in.
And here is the final fitment – as on-the-money as I cared to achieve. At this point, all of the bolts were tightened to specifications, and I finished drilling and mounting the transmission cross-member. The crane, jackstands, and blocks were removed.
Next up: Well, I have a heavy thing living inside another heavy thing, but with no metaphysical connections to it. I now began the “1000 little things here and there” stage. First up, fitting up the driveshaft to the transmission and mounting the 38 gallon modified fuel tank.