RIP: she won't fly! The engine mount crossmember (the bit that connects the motor mounts to the chassis) is narrower on the U42T and rides lower off the frame. The mounting holes on the U19T block also don't line up exactly with the ones on the hemi block. You can just barely wiggle everything in and bolt it all together, but it's not straight nor level and it wants to tear the mount rubbers up before it's even started. Plan B: back into the parts truck. The story: I spun a bearing on my 6V non-hemi 3G83 and found a parts truck with a mostly-finished rebuilt 12V hemi for less than a new engine. After replacing some bent valves and lapping in a new set, I'm reinstalling the engine and transmission. I'll try to document everything as well as possible here in case anyone else decides to build something similar. Mounting the Engine and Transmission The U42T uses a different style of engine mount and a different mounting frame (the U-shaped bit that attaches to the frame rails and has the engine mount arms bolted to it). The 19T has a bent tube frame: The u42T has a welded frame, it seems much less rigid and I haven't attempted to use it. The first issue I've found is that the transmission mounts on the 5MT do not fit on the U19T frame. This is the 5MT on the U42T: When I line the motor/trans up under the U19T, the mounts are too far back, and the center mount is an entirely different style: This is interesting - the distance between the transmission mating surface and the face on the transmission casting that the rear mounts bolt to is the same for both the 4MT and the 5MT. This means that either the frame crossmember is in a different place or that the engine sits farther forward using the U42T engine mounts. If it is the latter, I may have a problem with the driveshafts (I haven't measured these yet to see if they're the same). The U19T mounts look like this (the center mount is removed): The passenger side mount is swept forward; hopefully it'll fit between the 5MT and the U19T frame crossmember. The center mount is an entirely different design, but I think I can pull it off of the 4MT and mount it on the 5MT with a bit of grinding to fit. Engine Mounts The newer truck uses three-hole mounts (three bolts into the block) on both sides, and the older one uses a two-hole mount on the passenger side (possibly both - I am hunting for pictures). Because the two-hole mount threads on the 12V block had never been used, they needed a good cleaning with a wire brush before the bolts would go in. When I get all the mounts together, I'll finish working the engine into place. I've laid the engine out on a sheet of plywood empty of oil and exhaust side down, slung it up on two ratchet straps and I'm carefully working it into place. Doing it this way requires that the block be bolted in first; you can't pivot the engine/trans assembly up using the transmission mounts or the fan pulley hits the frame (even with the fan removed). I'll update more next week!
After a day of fiddling about and trying to wrestle the engine into its home, I can confirm that the U19T mounts will work to hold the U42T engine. It almost seems as though the trans mounts and engine mounts are maybe 1/4" too close together which puts a bit of tension between the front (engine) and rear (transmission) mounts, but I could be imagining it and I have one more mount to install. When I get back under it I'll go around and make sure all the mounting plates are properly seated against the frame. For now, it looks like this at the transmission end: The middle transmission mount needs the attention of a bench grinder, but it will fit with a bit removed: With those three mounts in and no other support, I thought I'd test fit the driveshaft to make sure I wasn't wasting my time on a lost cause, and it fits beautifully: That's where I left it for the night. If you are installing one of these motors without a jack, you can make it a one-man job if you're careful: I dropped the engine onto a clean sheet of plywood with the manifolds off, shoved the plywood under the truck so the engine was roughly in position and then carefully stood it up on the oil pan and slung it up on two ratchet straps (one just behind the transmission bolting flange and one at the rear of the transmission). Keep the rear end low so the transmission jewelry clears the frame mounts when you tilt the engine to its final angle. The center of gravity is behind the bolting flange so it doesn't tend to tip forward, but it is quite top-heavy so move slowly and don't stand beside it (stay behind it our outside of the frame). You're then going to tilt it a little more than 45 degrees to the left; be very careful that it doesn't go all the way over. It doesn't hurt to have a jack (with a wood softener) under the pan to control the tilt until you're in position to install the drivers' side (upper) mount. You can tighten this one down; there's enough flexibility in the rubber to let it move as needed. Keep the jack in position and install the bottom mount - you'll need to lift it up past its final position and lower it into position to account for the bolt stickout in the mounts. This part took some fiddling. I had the best luck loosely fitting the mount to the frame first and threading the nut on half way, then fighting the engine against the straps to make the three mounting holes on the engine block line up and tightening those bolts down. Tightening the nut on the other side was the last step that pulled the engine into its final position. So far, everything fits - I am a little apprehensive still, but I look forward to running this unit with a 5speed in the near future.
See edited first post: engine mount crossmember and block bolt hole locations are different, this swap can't be completed without fabricating new mounts. I'm going to leave it there for now and rebuild the U19t motor to replace in the older truck.
