Engine Swap

The Old LT5 Was Good, But This One Is Better!

Andy Bolig Feb 1, 2001 0 Comment(s)

Step By Step

First, prepare the shifter. Pop the shift pattern cover and remove the wedge that holds the shift handle in place; then unscrew the handle.

The console cover is held in place by three 7mm screws.

There is an Allen screw that keeps the shifter boot in place.

Once the console is loose you can lift it up enough to disconnect the cigarette lighter.

Remove the four bolts that hold the boot in place. You’ll have to unsnap the boot from around the base. When you install the transmission again, snap the boot back in place.

Disconnect the exhaust and remove the system from the car. Dropping the system as one unit after you disconnect it from the exhaust manifolds works best.

George’s car has a set of headers instead of the stock manifolds, and we found that the best way to get the headers out was to remove all the bolts we could reach from the bottom, and then get the other three from the top.

We removed the driveshaft next. Because of the added horsepower and the fact that George will be doing some racing, we’ll install a driveshaft loop from Exotic Muscle. They have driveshaft loops that bolt right in.

Next we removed the transmission bolts and used a prybar to work the tailpiece of the transmission out of the driveline support. Have the transmission supported by a transmission jack or some other means. The ZF transmission is heavy, and you don’t want to damage the case—or yourself.

Next we removed the clutch slave cylinder. Leave the lines connected so you don’t get any air in the system.

In preparation for removing the bellhousing, note that there are several ground wires that connect to two of the bellhousing bolts. When installing these bolts again, use the two bolts just as they originally were. Do not put all of the grounds on one bolt because it could cause cross-talk among the different components that use those grounds. There’s a reason why there are several grounds on the bellhousing.

With the pressure plate and clutch assembly removed, we were greeted by this freckled flywheel—a sign that it was very hot at one time. We’ll definitely send this flywheel out to get checked.

Be sure to unhook all of the sensors before you try to remove the engine. The connectors are plastic and will break easily, so make sure they’re all disconnected.

George’s ZR-1 has nitrous, so we needed to disconnect the lines. Make sure the manual valve at the tank is closed before you ever crack a line on a nitrous system.

We evacuated the air conditioning because we’ll be using the compressor from George’s engine. We had to remove the accumulator to get to some hoses that needed to be removed.

Disconnect the TV and throttle cable. There are a few clamps that hold the cables to the plenum.

The LT5 has an intricate hose assembly that flows coolant to each head.

There are only four connections that must be disconnected, and the whole system comes out as one piece.

The LT5’s computer is supposed to be removed along with the engine, but we decided to remove the plenum and unhook the wires instead of removing the computer.

There are a lot of wires and vacuum hoses under the plenum of an LT5.

All the coils for each cylinder are under the plenum, along with the vacuum system for the secondary fuel system and all of the wires for each of the 16 injectors. There’s a lot going on under the plenum of an LT5!

Once we got the hoses out of the way, we could reach the oil-cooler lines and disconnect them.

After a final check that all wires and vacuum lines were disconnected, the engine mounts were unbolted, the hoist was hooked up, and we pulled a perfectly good LT5 out of a ZR-1.

No turning back now.

We removed the plenum on the LT5 that we’ll be installing in preparation for hooking up all of the wires and vacuum hoses. Also, pulling the plenum gives us a solid lifting point that we can still reach once the engine is installed.

With the engine in place, we tightened the engine mounts and lifted the engine with the hoist as we lifted the car so we could install the transmission. Here we have the freshly machined flywheel and clutch installed. The use of an alignment tool for the clutch plate will greatly reduce transmission installation time. (Remember—they’re really heavy.)

With a jack supporting the engine and the transmission on a transmission jack, we installed the transmission. Even with the clutch aligned it can take some wiggling to get the input shaft of the transmission coupled with the splines on the clutch plate. Once it was in place, we bolted the driveline support to hold it.

With the engine and transmission supported, we began hooking up the myriad of hoses, wires, and lines under the plenum. What’s different about this engine is that it doesn’t have the secondary fuel-system disarm. The valet key is now rendered useless, since the butterflies and valves have been removed.

We replaced the compressor and worked on connecting up the hoses on the front of the engine and installing the drive belt.

After everything was hooked up (and double-checked), we installed the plenum using new gaskets. You can see the fuel lines on the passenger side up on the windshield. Always make sure the fuel lines have good O-rings before you connect them.

After connecting all the hoses, lines, and wires on the top of the engine, we began installing the headers, again, installing as many bolts as possible and then letting the car down to get the rest from the top. Notice that we did not remove or install a starter. That’s because the starter is also under the plenum, underneath the coil packs, and faces out toward the flywheel. There’s a drain tube to keep this area under the plenum from filling up with water, but it doesn’t always work. Some people have cleaned their engines with water and found out that the drain tube was plugged when their Corvette wouldn’t start.

The exhaust system is bolted back on as a complete system. We finished by filling the engine with coolant and oil, and charging the A/C system.

A black LT5 is a lot like a white elephant. Very rare and extremely powerful. When George Bonafide located this black, MerCruiser-prepared LT5, he knew that more than just black wrinkle finish separated it from the original engine in his ’90 ZR-1. The history of this engine includes names of speed merchants who have set records with other ZR-1s, so we knew there was definitely something special about this engine.

George purchased two engines, which were reportedly part of Tommy Morrison’s collection. Follow along with us as we show what it takes to remove and replace an LT5.

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