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Bringing a Corvette Big Block Back From Lethargy - Undercover Moves
Getting Down And Dirty With Big-Block Underhood Techniques
Nov 13, 2008
Mechanicsville, VA 23111
BJ's Wholesale Club
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Bringing a Corvette Big Block Back From Lethargy - Undercover Moves
All C3 big-blocks can look this good with a little work.
Like we said, it was rough under the hood, but it was all there. It looks like the engine was rebuilt as it appeared from under the filth. Another giveaway to a rebuild was that the cylinder heads were installed on the wrong side as the water temperature sensor was now on the passenger side, and the temp sensor wire was snaked around the engine compartment. Down the road we'll attempt to remove the plug in the cylinder head to install the temp sensor in the driver-side cylinder head and wire the temperature sensor correctly.
Don't be afraid to spray the engine cleaner all over the engine and compartment, just be sure to cover the carburetor and all open holes. Greased Lighting works well because it rinses any oily and greasy residues away. We spray the cleaner on and then let it soak. If it dries, just apply another coat of cleaner. Avoid spraying the cleaner on the exterior paint. A few minutes won't hurt, but prolonged exposure will hurt the finish.
Rinse the area well. You'll be amazed how much better things look. This is just one of many cleaning and rinsing cycles we did. After each cycle, we blew off the water with compressed air and let it dry before reapplying the cleaner. It appears after cleaning many engine compartments that dry engines clean best. If the area is wetted first, the cleaner just doesn't work as well.
Before we clean the engine compartment, the hood should be cleaned. Let all the excess cleaner end up on the engine while you're working. We used a tire scrub brush to scrub the underhood area. Then we rinsed the underside of the hood carefully, keeping most of the rinse water off the engine. Remember to rinse the headlight and radiator core support area also.
Scrubbing was necessary to remove the build-up of oil and grease residue. Brass brushes work best and keep the surfaces original finish intact. Use the brass brush on all surfaces-cast iron, S/S, and aluminum-as it will not scratch like a steel brush. Scrub the area and reapply the cleaner until you see the original surface before rinsing. This takes plenty of time and patience, but is very rewarding when you see the difference. If the engine had been cleaned annually, this could have been avoided.
After we removed the carburetor, the intake manifold gets a final cleaning with carburetor cleaner to loosen the baked-on build-up. Spray the carburetor cleaner on and let it soak. If any spots are stubborn, use the brass brush to get into tight areas. Notice the plug in the PCV valve grommet. Make sure all holes stay plugged throughout the cleaning process. Oh yes, carburetor cleaner will also remove paint. Avoid letting carburetor cleaner sit on the engine paint. At the very least, it will discolor the engine paint.
The valve covers were rough, but with the right cleaner they should look very nice again. We use the rubbing compound to remove the rust and corrosion. It does an excellent job with less elbow grease without scratching the chrome. Now's the time to polish the cover before everything's in the way.
We're installing the new distributor shaft and Pertronix Ignitor kit Zip Products provided for the 427 project. We cleaned up the original distributor housing and gave it a coat of Krylon semi-gloss black paint and replaced the distributors vacuum advance unit. The Pertronix unit is simple to install. We like to remove the distributor and at least check out the bushings before installing the kit.
Before we set the distributor in place, we coat the tachometer driven gear liberally with Zip Product's supplied lube. You should apply lube to the distributors driven gear also. Once the Zip Products tachometer driven gear is installed, the distributor should be spun by hand to feel for any rough spots. We had to file the ends of the teeth slightly to eliminate some minor binding we found when we rotated the distributor shaft. If you feel any binding while turning the distributor shaft, gear damage will result. Take the time to check for smooth operation.
We're showing the old tach cable that is bent at 90-degrees from improper distributor installation. This is a common problem because many GM techs put the distributor in the incorrect position since Chevy engines without shielding have the distributor closer to the intake manifold runner. Before you install the distributor, look closely at the distributor base where it sits on the intake manifold. You'll find nicks from a punch that marked where the distributor was positioned from the factory.
When we dropped the distributor in place, we moved the distributor shaft one tooth clockwise from where the rotor was originally and moved the distributor housing to the backside of the ignition shield support to eliminate tach cable bind. We removed the ignition shield support brackets and painted them gloss black like they should have been.
We're now shifting gears and moving to the carburetor installation before wrapping up the ignition system. The stainless steel separator shown is commonly left off when the carburetor is replaced, which can cause carburetor base plate damage. The S/S plate was used to keep exhaust gasses from reaching the carburetor base plate. Exhaust heat is routed through the cylinder heads and intake manifold when the heat riser on the exhaust manifold is closed. The heated exhaust helps warm-up the engine and aid cold weather drivability. Another common mistake is to put a gasket between the S/S plate and carburetor. The gasket between the S/S plate and intake manifold should also be an exhaust proof material, not a paper gasket.
Small things like this carburetor return spring make the difference. The original spring was thrown away years ago, and a door closer spring was installed. Stiffer springs wear out the carburetor's throttle shaft quickly. We were able to brass brush the throttle cable mounting bracket, leaving the original coating. Once any bracket is chemically or mechanically stripped, a coating must be reapplied to prevent corrosion.
Since our original carburetor's air cleaner mounting stud was missing, Zip saved us with the unique original-type air cleaner stud. As you can see, the intake manifold looks much better, and things are starting to take shape. We cleaned the exterior of the carburetor with the carburetor cleaner before installing it on the intake.
Replacing the fuel pump isn't the easiest thing to do, but with the right tools, it isn't so bad. We found that a long extension with the universal socket that can be used from the fenderwell works best. You can see the extension is coming in from below the upper control arm. The fuel supply and return hoses were replaced along with the fuel pump. We replaced the pump because of the debris in the tank. This debris fouls the fuel pump check valves, and the pump output is diminished. Zip supplied us with an aftermarket pump because we didn't want to fill a new correct pump with junk. After we run the engine for awhile, and everything checks out OK, we can change to a numbers-matching fuel pump.
We installed the Zip Products-supplied spark plug wires, paying close attention to where the shielding ends on the plug wires. The instruction sheet proved to be correct, and they also mention the correct distributor cap placement. If the distributor is installed incorrectly, the plug wires won't fit properly.
We always apply a dab of silicone dielectric grease to ease plug wire boot installation and removal. Too much grease and the boots want to slip off. A dab the size of a wooden match works best. On at least half of the plug wires, we had to grab the terminal in the spark plug end and pull it out to meet up with the edge of the boot where the size increases to accommodate the spark plug porcelain. You should feel a click when the plug wires are installed properly.
We installed the Pertronix Flame Thrower ignition coil to pump up the spark voltage. The Pertronix coil fits in the stock bracket and is shorter than the original coil, making plug wire installation easier. All wiring info is provided, and the coil connection terminals are provided in the Pertronix Ignitor kit. The original resistor ignition power wire coming from the harness should be replaced with an ignition power wire coming off the pink wire at the ignition switch.
One of the original pieces we cleaned up and reinstalled was the ignition lower shield. The Pertronix pieces are a good choice since you don't have to remove the cover and shielding to access the points all the time. Once the shield is in place, the plug wires can be installed. If the distributor is in the correct position, the plug wires and shielding grounds will fit properly.
These are the small things that make engines run well. PCV valves have calculated vacuum flow rates for the engine they were designed for. When incorrect PCV valves are used, performance suffers. If the flow rate is too low, engine contamination from condensation can occur. We also replaced the PCV valve grommet to keep vacuum and oil in the engine.
We wanted to change the variety of cooling system hose clamps that the engine had with OE-style clamps from Zip. Everybody hated these clamps that worked with them regularly because they were difficult to release until you figured them out. Place a screwdriver between the hose clamp band and the hose, then give the screwdriver a twist to release them.
Ever since we first started the car, we had no oil pressure showing on the oil pressure gauge. We found the block fitting was plugged, and the oil line was cut. Zip Products supplied the correct steel line and fittings. We also used their line bracket to replace the missing bracket. We weren't overly concerned since the engine was quiet, but it's nice to know the correct oil pressure is there now that we'll be driving the Corvette occasionally.
We moved inside the car to remove the center gauge cluster and replace the plastic oil line. The first piece to remove is the map pocket dash panel and then the wiper switch plate. The radio knobs and the nuts that hold the radio to the plate must be removed to pull the plate out of the console and dash. Originally, the center gauge cluster had two 31/48-inch hex nuts holding it to the center console that must be removed. Most of the time, the nuts are left off during reassembly. If the plate is tight to the console, the nuts must be removed.
Now we can install the new plastic oil line on the oil pressure gauge. Watch the routing of the plastic oil line. It can be pinched during dash reassembly. While we were inside the car, we also replaced the accelerator cable. The accelerator cable on the '69 has a 71/416-inch hex-head screw directly above the accelerator pedal assembly, holding the cable on the firewall from the inside. Job done.
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