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1968 Ford Mustang Engine SwapFitting 10 Pounds Of Engine In A 5-Pound Engine Compartment From the June, 2010 issue of Modified Mustangs & Fords By Mark Houlahan Photography by Mark Houlahan
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Tech | Engine Bay Preparation
We've gotten things a little out of order with our '68 Mustang project buildup. The last few build stories have focused on our bodywork and the custom modifications we've done to make the car stand out from the crowd. Of course one of the stand out items for this build is what's going on underhood, and that's our '06 Mustang GT 4.6L Three-Valve we're swapping into the classic engine compartment. So before we wrap up our bodywork and actually shoot the color coat of Dark Shadow Gray Metallic, we had to wrap up all the little details that'll get our engine and transmission fitted to the chassis. The main reason, of course, is we don't want to be doing any cutting/grinding or welding on a freshly painted car. We also plan to paint the engine compartment body color, so any major changes to the inner fenders, firewall, and so on all need to be handled now so we can perform final bodywork in these areas and paint them the same time the body is painted. We showed readers some general modular engine fitment ideas in the May '10 issue with our "Big Three" story, where Kevin Tetz outlined the major hurdles of installing the wider mod motor. We already have our Heidts Superide II front suspension crossmember in place (and we'll be showing everyone more of the actual suspension and front brake fitment here in an upcoming issue) so really all that's necessary for fitting the engine and trans is to find final placement of the assembly, ensure our driveline angles are right, and then weld up our engine and transmission mounts. We've trailered our project over to Classic Creations of Central Florida, the shop responsible for all of the great bodywork, which will be applying our paint as well, to help us with engine fitment. It has installed several Heidts front suspension kits with custom engine fitment issues (big-blocks, Clevelands, modulars) so we knew that our project was in good hands. With the welding work completed, the engine and transmission bolt in as if the car was designed for the modern drivetrain. So check out this month's progress and stay tuned as we wrap up the fastback's paintwork with some color and move on to plumbing, brakes, wiring, interior, and more, hopefully wrapping up our project by the end of the year.  Currently Heidts does not...  Currently Heidts does not offer any engine mounts other than small-block Ford for its Mustang kits. While some new and exciting products are coming from Heidts soon that will include engine-mounting kits for more of Ford's engines, we had to fab up our own for the mod motor. Luck saved the day when we heard of The Mustang Shop through our friend Doug Glad, editor of Car Craft. The Mustang Shop offers several mount kits to fit the mod motor (one of its specialties) and we used its cut-and-weld-to-fit urethane mount kit, shown being mocked up here.  We've had our Performance...  We've had our Performance Automatic 5R55S five-speed auto trans for a little while now and we bolted it up to our 4.6L modular so we could get the whole thing down into the engine bay and see what "gotchas" were waiting for us.  Horror stories abound about...  Horror stories abound about modular engine oil pan fitment (or lack there of) in custom installations like this, so we were elated to see that the stock '05 and up Mustang rear-sump oil pan cleared our crossmember perfectly. But the real question: Was the engine sitting low enough?  Since we didn't want to weld...  Since we didn't want to weld anything in the wrong place before the pros at Classic Creations looked at it, we used a system of wooden shims and support straps to get the engine where it needed to be....  ....Thankfully the intake,...  ....Thankfully the intake, now installed for fit check, cleared the fiberglass Shelby style hood from Mustangs Plus (for a second we thought we'd have to have the oil fill cap sticking through the hood!) and we still had a finger's width between the oil pan and the steering rack.  Placing the engine rearward...  Placing the engine rearward helps in vehicle handling and weight distribution, so we decided to set the engine as far back as possible without creating major fabrication headaches. With the engine where we wanted, it still cleared the crossmember and steering, but we were now butting up against the firewall. Some trimming and a little metal work will fix that.  Once we arrived at Classic...  Once we arrived at Classic Creations with our project in tow, the first order of business was leveling the car on work stands and then cutting....  ....out the firewall area,...  ....out the firewall area, marked up with a grease pencil, so there would be sufficient room to formally align the engine.  Getting under way with the...  Getting under way with the permanent fitment, the engine is centered side to side between the framerails in the engine bay. This ensures that there's equal header clearance on each side (for one thing).  Once centered, the engine...  Once centered, the engine is then leveled side to side as well. Ensuring the engine is level prevents issues with a multitude of things including shift linkages, hose fitment, fuel feed (carb'd applications), and more.  Finally, from under the car,...  Finally, from under the car, the engine and transmission angle is measured and set using a quality floor jack that doesn't bleed down. You don't want your measurement changing slowly while you're elsewhere working on the car.  With the engine and transmission...  With the engine and transmission measurements "locked in," the Mustang Shop mount kit is mocked up against the Heidts crossmember. Due to the engine setback, the mount legs ended up sitting rearward of the main crossmember by about half their width.....  ....The mount legs are notched...  ....The mount legs are notched to fit against the crossmember, clamped in place, and then tack welded. You don't want to do any finish welding as you'll build too much heat in the mount and melt the bushings.  To realize just how wide the...  To realize just how wide the modular engines are, you can see that the left cam cover just barely clears the master cylinder mounting holes, while the passenger side cam cover completely covers the heater....  ....hose and A/C line openings...  ....hose and A/C line openings and encroaches on the blower motor opening. No worries though, as our aftermarket A/C unit allows for custom hose routing/length so we can route them farther to the right or even through the cowl side.  Tacked in place for now, Classic...  Tacked in place for now, Classic Creations' Danny Gaydos (who has been behind the MIG welder for this whole project) made up this simple firewall patch with two bellhousing bolt access holes. The remainder of the firewall patches will be handmade and welded into place once the engine is back out.  When we first replaced our...  When we first replaced our Mustang's floorpan we opted to leave the crossmember out between the two front floor supports. This is normally where the factory trans crossmember is bolted to, but we knew with our five-speed automatic we'd be adding a custom crossmember. The Ron Morris Performance Unicross crossmember was the perfect answer. This part is the Superman of crossmembers, allowing you to bolt in just about any transmission you can think of.  The Unicross is a simple measure,...  The Unicross is a simple measure, drill, and bolt-in affair for most projects. After getting our driveline angle determined earlier, it was a matter of fabricating a trans mount for the new-fangled 5R55S (it has but a single threaded lug and Gaydos modified a classic Mustang....  .....mount to work) and then...  .....mount to work) and then affixing the Unicross to the mount. This determined where the crossmember's mounting brackets would go on the floor supports; a couple of drilled holes later and our transmission was secure.  Now that the engine mounts...  Now that the engine mounts were completely tack welded and the Unicross crossmember located and its mounting brackets bolted in, the 4.6L Three-Valve could be removed from the engine bay once again to allow final welding of the mounts.  Gaydos fabricated small corner...  Gaydos fabricated small corner gussets for the mounts, from the main mount leg to the support bar (shown here) as well as from the main mount leg to the Heidts crossmember while finish welding all of the mount's contact points with the crossmember and the framerails.  A quick pass with the grinder...  A quick pass with the grinder cleaned up the finished welds. While not seen by most people, especially once the engine is in place, all of the engine compartment welds will be body worked and smoothed before applying body color paint to the engine compartment.  Taking a step back, we can...  Taking a step back, we can see just how much room the typical Mustang II frontend, with the shock towers fully removed, really offers for engine fitment. The firewall will be partially smoothed and other small details will be attended to in order to make the engine compartment ready for painting.  We can't forget the engine...  We can't forget the engine side brackets of the mount kit either. These were tack welded together when the engine was in place. Here Gaydos has removed them from the engine and is finishing welding them.  After taking the engine in...  After taking the engine in and out at least four times, we're getting pretty good at it. Once again the engine is dropped in place and the mounts bolted up to check for fit. Everything lined up nicely and the mount's through bolts slid right in. We'll be taking the engine out again once we get the project back to HQ.  When it comes to engine swaps,...  When it comes to engine swaps, probably one of the most troublesome areas to tackle is the exhaust. It's tough enough installing an engine that was never factory installed in your project, but then throw in possibly lowering the engine or setting it back in the engine bay and it gets worse.....  ....We thought we got lucky...  ....We thought we got lucky when we test fitted a set of BBK long-tube headers designed for the '05 and up Mustang. The driver side header, shown here, fit like it was designed for the swap, but when we tried to bolt up the passenger side header our luck ran out. Several dimensions just didn't work in our favor. We're still trying a few ready-made options, but we might be heading down the path of custom-made headers. Stay tuned for more.
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