After 30 years and 75,000 miles, my original L-48 350 engine was still very dependable and running solid.  However, after installing my TKO 500 5 speed kit, I decided I wanted some extra horses up front.  I also wanted to keep my numbers matching engine so that the car can be restored back to original at some point.  After many hours of research, I decided to purchase a new ZZ4 crate engine from GM with specs as follows:

GM part number 24502609 - ZZ4 Crate Engine, 350 Generation I long block, includes 4 bolt main caps, nodular cast iron crank with one piece rear seal, 10.1-1 Compression Ratio hypereutectic pistons, 5.7" PM rods, 58cc aluminum angle plug heads, hydraulic roller cam (lift .474"/.510", duration. @ .050" = 208'/221'), 1.5 rockers, lightweight valve train with 1.94"/1.5" valves, valve covers, dual plane 4-barrel carburetor aluminum intake manifold, damper, 5 quart oil pan with windage tray, water pump, flex plate and rear mounted HEI distributor with vacuum advance.  Passenger side dipstick and center bolt valve covers.  355 HP @ 5250 rpm, 405 ft./lbs. torque @ 3500 rpm.  Requires premium fuel.

Preparing the ZZ4 engine for installation in a C3 is not a major deal but there are some things of which you need to be aware and I will discuss these in this documentary.  One of the things that you will want to know is 'what parts from my old engine will fit on the new one?'  Well, let me begin by saying that lots of parts are transferable including, water pump, Quadrajet, exhaust manifolds, all pulleys, fuel pump, motor mounts, all brackets for A/C and alternator.

The ZZ4 comes with a long water pump which of course is not correct for a C3.  The C3 requires a short pump with a 3/4" shaft.  The timing cover on the ZZ4 is a composite material and one of the bolts retaining it must have the head ground down to clear the back of your original pump.  In my case, I did some research on water pumps and I found out that Edelbrock make an aluminum pump for the ZZ4 application in C3 Corvettes.  It is the Victor series with part number 8812.  It also has the correct shaft diameter for your clutch fan and the indentation to clear the problem bolt on the timing cover. 

The ZZ4 has D-Port cylinder heads and angle spark plugs.  Although the original cast exhaust manifolds will bolt on and will work fine, the manifold openings should be ground on the top sides to match the ports on the heads.  The angle plugs make for a bit of a challenge but there is sufficient clearance with the original manifolds.  I wanted to preserve my original manifolds so I researched alternatives.  Since my car already had the original style side exhausts which I wanted to retain, I needed to find some short style headers that were designed for D-Port heads with angle plugs.  Patriot make ceramic coated headers for this application so I went with those.

The ZZ4 stock aluminum intake is slightly higher than the one on your original engine.  Having said that, there is still clearance under the later C3 hoods for the original QuadraJet and air breather.  If you plan on using your original carburetor you should have it rejetted to take full advantage of the added performance of your new ZZ4.  I decided to go with different carburetion and settled for a Barry Grant Speed Demon.  Barry Grant builds a 650 Speed Demon especially for the ZZ4.  It is basically a 'take out of the box and install' application.  Because I have a standard transmission I went with mechanical secondaries and electric choke.  I fabricated a throttle and cruise control bracket from the original QuadraJet bracket.    Since the electric choke requires a constant 12V power supply while the engine is running, I tapped into the 12V supply line for the heater motor.  The 12V supply line for the wiper motor will work equally well.  I also fabricated a bracket for the A/C idle solenoid which I mounted towards the front of the intake.  For an air breather, I installed a dropped 14".  The filter is 3" in height.

Update:  I was having problems with engine warm up and discovered my problems were with the electric choke.  I have since removed the choke completely and the engine runs just fine without it.  If was doing this again, I would not buy the Speed Demon with the choke.

One of the components from the original engine that is not transferable to the ZZ4 is the flywheel.  The ZZ4 uses the one piece rear main seal and the bolt pattern is smaller than the older 350 engine blocks.  I purchased a new flywheel from Keisler Engineering.

A couple of other details of which you should be aware include the sending unit for the temperature gauge.  On the old engine, the sending unit is located on the left cylinder head just directly under the front side of the exhaust manifold.  The location is the same on the ZZ4 head but the hole is smaller.  There is, however, a plug on top of the intake directly under the thermostat housing that can be removed and the sensor installed there.  Your wire connection will reach without a problem and your gauge will read accurate at that location.  The ZZ4 does not come with the an oil filter mount installed.  You can transfer the one from your old engine or purchase a new one from GM.  I am not sure why GM does not include that part.

The engine mounts from the old engine will bolt right on.  I purchased a new set of poly mounts from Summit.  Another thing that I did before the install was replace my 1.5 stock rockers with GM Performance 1.6 roller rockers.  Since the 1.6 rockers require more head room, I also installed a pair of polished aluminum valve covers for the 1.6 application.  I installed a set of 90 degree boot GM Performance plug wires and a GM loom kit to route the wires safely away from the headers.  I used my original fuel pump along with a braided fuel line kit from Summit.

After installing the flywheel and clutch housing, I dialed in my crank shaft relative to the opening in the bell housing.  The tolerance for the TKO transmissions are much closer than for the original Muncies.  I ended up having to install offset dowel pins in order to achieve the necessary clearance specifications.  Next, I installed an 11" clutch and pressure plate.  Since I was using a hydraulic clutch release bearing, there was no need to install a clutch fork or bearing as it is attached to the front of the TKO.

All that is left to do now is drop the new ZZ4 into place.  You will need to remove the spark plugs, headers, fuel pump, and distributor in order to get clearance from all the obstructions.  It is your decision whether or not to install the transmission along with the engine.  In my case I installed the engine and transmission separately.  If you do not have a removable transmission cross member, then I highly recommend that you install the engine and transmission as a unit.

After the engine is in place you can install the headers and hook up your exhaust.  Install the spark plugs, fuel pump, fuel lines, power steering pump, alternator and A/C compressor.  Install all pulleys, fan and belts.  Reconnect the radiator, heater hoses and fill radiator with coolant.  Install starter, connect wiring, and vacuum hoses.  Before you start turning over your new engine, it is critical that you prime the oil pump and ensure that oil is reaching the top of the engine.  Use a proper engine oil priming tool to perform that task.  The last thing to do is install the distributor and ignition wires.

Follow the startup instructions that come with your new engine.  My engine fired up after about three rotations.  I had a small fuel leak and had to shut down the engine after a few seconds.  Make sure you check for fuel and coolant leaks on first startup.

New engine picked up from my local GM dealer

Checking flywheel run out

Checking header fit

Fabricated bracket for cables

Removing original engine

Checking accelerator and cruise cable travel

Car stance with new engine (Yes you do have to address the lighter engine)

ZZ4 badge goes on engine hood

Checking air cleaner fit and clearance

New 1.6 roller rockers and valve covers installed

Installed manual shutoff valve in heater supply hose

Installed polished radiator hose

Reservoir for hydraulic clutch system

Almost ready for the open road!