Revision Corvette ZR-1 model year 1990 #125

[Thomas ZR-1]

Thank you guys...here are the next steps:

[Thomas ZR-1]

11. Assembling engine compartment

After cleaning all the engine periphery, the parts could be refitted. All wiring harnesses were cleaned up and all damaged electrical plugs were replaced.

[Thomas ZR-1]

...and some more:

[Thomas ZR-1]

Finally the large hood with new headlights and overhauled torque motors went back to cover the compartment.

[Thomas ZR-1]

12. Engine rebuild

Now it was time for the heart of the beast: the LT5 engine. As I told you I did the test drive with the ZR-1 before the project started. The engine ran pretty well but was in an ugly leaky condition?remember the basics:

[Thomas ZR-1]

The engine was developed at the LOTUS Company in Great Britain for the Corvette ZR-1. There was nothing in common with the standard C4 Corvette engines until the firing order (1-8-4-3-6-5-7-2) and the transmission flange. One of the main features is the four overhead camshafts. They drive the 32 valves via bucket tappets. The complex is driven by one primary and two secondary DUPLEX drive chains. The valve train is resistant until 8000 RPM. This construction is unique in the whole Corvette history until today. The camshaft timing is quite time-consuming and should be done very precisely to have the engine running smooth and powerful later on.

The engine was disassembled until it`s last screw and washer and all parts were cleaned up very well. At the fitting all seals and gaskets were new, the starter got new contacts, the alternator new carbo brushes and bearings, the belt tensioner a new main spring with base plate and new pulley. As a precaution I renewed both fuel pumps in the gas tank including the fuel filter.

Before fitting the engine some inner engine components had to be checked. I measured out the main and rod bearing sizes at the crankshaft. All diameters were good and got polished at the end. The NIKASIL coated cylinder liners and the pistons with piston rings (ring gaps) were checked as well, result: all sizes in perfect condition.

[Thomas ZR-1]

Next I started with the cylinder heads. All valve seats in the heads and on the valves were ground.

[Thomas ZR-1]

Unfortunately the 1990 LT5 engines don?t have valve stem seals on the exhaust side (only the old-school O-rings). This changed with the 1991 model to reduce the engine`s oil consumption. So we ground a fitting seat on every upper exhaust valve stem guide.

[Thomas ZR-1]

Of course both cylinder head sealing surfaces got ground as well to have perfectly tight cylinder head gaskets later on.

[Thomas ZR-1]

At the end the heads were fitted with 32 new valve stem seals and two new actuators for the eight secondary port throttle flaps.