Rebuilding a Chevy Straight Six – Part 6

Rebuilding a Chevy “Stovebolt” Six Part 6

Finishing and reinstalling the engine

It’s taken us five installments, but we’ve finally come to the point in our engine rebuild series where we can install the distributor, clutch, and various pumps and accessories, set the engine back in the car – and enjoy the smooth performance of a restored powerplant.

The Clutch

Clutches are inaccessible once the drivetrain is back together, so it is advisable to install a new clutch disk, and a new, or rebuilt, pressure plate assembly and clutch release bearing (throwout bearing) any time you have an engine out of a car for overhaul. Take your old clutch assembly to the parts house and have them match the parts. Surprisingly, clutches for cars made during the past 5O years are fairly easy to locate, because most manufacturers’ products, such as Borg and Beck, Long and Chevrolet were used in several makes for years at a time, without change.

The Flywheel

If you haven’t refurbished your flywheel, do it. Flywheels take the heat in cars equipped with standard transmissions. They often warp, become glazed, or even crack. In a previous installment (Part 3 – December 1995), we advised that a flywheel be resurfaced at the machine shop while your other engine parts are being machined. We also recommended that, after the flywheel is properly surfaced a new, or rebuilt clutch assembly be attached and the components balanced to prevent vibrations during acceleration. Also, both the clutch assembly and the flywheel should be marked, so you can put the clutch on the same way it was when it was balanced.

Bolt the bell housing (also called the clutch housing) onto the engine, making sure any shims are reinstalled as they were when you disassembled the engine. Bolt the flywheel onto the crankshaft of the rebuilt engine with new bolts of the correct hardness, (check your manual for hardness specs or inquire at a transmission shop) and use new lock washers or other locking devices as required for your application. Evenly torque the bolts to the correct specifications according to your shop manual. (On our Chevy the torque is between 55 lb.-ft. and 65 lb.-ft.) Never attach a flywheel to an engine with ordinary, hardware store bolts. It is possible such bolts will break, and a loose flywheel can explode like a hand grenade when subjected to high revs.

With the help of a pilot tool (available at auto parts stores), slip the clutch disk in place against the flywheel. Attach the clutch assembly to the flywheel and evenly tighten its bolts one-half turn at a time, to the correct specs for your make. If you don’t tighten the clutch assembly evenly, you run the risk of distorting it. Remove the pilot tool, then lubricate the pilot bearing (it’s the little bushing in the center of the flywheel) with graphite grease. Don’t overdo it. Too much can leak onto the clutch lining ruining it. Pack the throwout (clutch release) bearing with grease and slip it into its yoke. put a little grease on the yoke pivot point too. Make sure you install the throwout hearing facing the right direction. More than one mechanic has put a bearing in backwards, and damaged the clutch and bearing when he ran the engine.

The Transmission

On some cars, it is easier to attach the transmission to the engine while they are both out of the car. With our six-cylinder, standard-shift ’57 Chevrolet, installing the transmission is easier after the engine is in the car because there are no crossmembers in the way of the transmission.

However you do it on your car, here are some installation tips. Put the transmission into high gear which is direct drive. Put locator pins into the upper bell housing holes. These can be fashioned by cutting the heads off of a couple of long bolts that are the same diameter and thread type as the originals. Slide the transmission into place. You may have to slightly turn the U-joint yoke to get the splines on the clutch shaft to mesh with those on the clutch disk. Remove the locator pins and tighten the bolts evenly, but never tighten the bolts until you are certain the transmission is properly meshed into the clutch disk.

Adding the Accessories

The final assembly of the engine with all its pumps and gadgets requires a little planning. Carefully examine everything before you start. Some items, such as fuel pumps, carburetors and fans can get bumped and damaged when reinstalling the engine, so you may want to wait until your engine is in the car before installing them. On the other hand, if these items are difficult to reach with the engine in the car, you may want them in place when you cautiously drop in the engine.

Here are a few pointers: When you attach the fuel pump, smear a little grease on the actuating lever, then make sure it is properly engaged on the camshaft. On some engines, the lever on the pump goes over the cam, and on others it goes under it. Check a shop manual to be certain of your application.

Always install a new thermostat of the correct temperature range when you rebuild an engine. New thermostats are inexpensive, and old ones can cause major problems if they malfunction. When installing the thermostat in the block, make sure it is oriented correctly. (This is very important on some cars.) Your shop manual generally will tell you how to install it and sometimes orientation instructions are stamped or printed on the thermostat. Use silicone sealer on both sides of the gaskets when installing the water pump. Let the sealer get tacky before attaching the pump. Don’t use any sealer on the gasket at the base of the carburetor when you install it because the atomized gas and air mixture passing through the carburetor will not leak out and the manifold heat could cause the sealer to burn.

When you attach the generator or alternator remember the belt only needs to be tight enough to prevent slipping. You should be able to deflect it between 3/4-inch and 1-inch in either direction with your fingers. If the belt is too tight it may snap and even if it doesn’t it can put unacceptable side loads on the bearings in the generator and water pump. It is usually easier to install the distributor after the engine is installed so do that later.

Setting It In

Because of its weight and size, installing an engine in a car can he dangerous. In addition the engine and car body can be damaged if the job is not handled with care. So by all means move the engine slowly and get an assistant to help you stabilize and maneuver it. Use a cherry-picker hoist or properly constructed chainfall hoist and a chain made of at least 3/16 inch welded links and at least 3 feet long. Never use your garage beams for support; they aren’t strong enough. In our case, the engine was on an engine stand and we began by loosening a head bolt at the right front side of the engine and one at the left rear, slipping a link of the lifting chain over each of the loosened bolts and tightening the bolts. (See the October 95 issue for tips on installing and handling the chain.) Slowly lower the engine or engine/transmission combination into your car. Attach the back motor mounts loosely then position the engine and attach the front mounts.
When you are sure everything is aligned properly tighten the mounts securely.

Reattach the drive shaft at the universal joint. Hook up the clutch linkage if your car is equipped with a standard transmission then adjust it to between 3/4-inch and 1-inch of free pedal travel before it starts to engage. Smear a light film of sealing shellac on the insides of the radiator hoses and slip them into place. Snug up their clamps just enough to prevent leaks and don’t over-tighten them as that could damage the hoses. Fill the cooling system with the proper water-to-coolant mixture (check the manual for your particular car) and fill the crankcase with oil. (10-30 weight detergent oil is ideal for our little Chevy six as well as most other automotive engines, but check your shop manual to be sure your car doesn’t have other requirements.)

Don’t be too quick to attach the fuel line from the gas tank to the fuel pump. First connect the wiring to the battery, starter, coil, generator, and voltage regulator. Polarize the generator by touching a wire from the battery terminal on the starter to the armature terminal on the generator. Otherwise over time you’ll burn the points in the voltage regulator.

With the spark plugs removed, crank the engine while holding your thumb over the number one spark plug hole. Stop when you feel a sudden blast of air. Insert the distributor with its rotor pointing toward the terminal for the number one cylinder. You may have to rotate the rotor slightly to get the distributor tab to drop into place on the oil pump shaft. By making sure the number one cylinder is in the firing position then installing the distributor as described above you avoid the possibility of installing your distributor 180 degrees out from its proper orientation which is possible to do on many engines. Remove the rotor from the distributor, and with the spark plugs still out and the fuel line from the tank still disconnected from the fuel pump, crank the engine until a little pressure shows on the oil pressure gauge. Replace the ignition rotor, install new, correctly gapped plugs, then attach the fuel line.

The Big Moment

Before starting your new engine, carefully inspect everything. Did you forget oil? Coolant? Are all of your electrical connections correct, clean, and tight? When you are completely satisfied that things are in order, start the engine. Let it run at fast idle until thoroughly warmed up. While it is running, look for leaks, and keep an eye on the oil pressure and temperature gauges, if the car is so equipped, or watch the warning lights closely. Also listen for unusual sounds such as grinding, rattling and clunking. If you detect problems, shut the engine off immediately and remedy them.

Set the idle speed at the carburetor (475 rpm on our standard shift Chevy, 425 rpm if it is Powerglide equipped) with the help of a hand-held multimeter. Disconnect the vacuum advance at the carburetor. Hook it vacuum gauge to the vacuum advance fitting on the throttle body of the carb and adjust the mixture screw for maximum vacuum. You may have to go hack and forth between the mixture screw and RPM screw to get it just right.

If your engine is equipped with solid lifters set the tappets to the correct specifications. This is done using a wrench a screwdriver and feeler gauges while the engine is thoroughly warmed up and running. (See Feb. 1995 “Tappet Tuning.”) If your engine has hydraulic lifters, start the engine and back off each rocker adjustment until it clatters then tighten it the requisite number of turns according to your shop manual. (Chevy six rockers should be tightened one full turn but a Chevy V-8’s rockers should only be tightened 3/4-turn.)

When you are satisfied that all is well take the car out for a spin. Avoid hard accelerations for the first thousand miles and don’t drive at a steady speed for long distances because the engine won’t wear in evenly. Change the oil at 500 miles and again after another 1000 miles. Check the break-in oil for any signs of water, bits of metal or burning.

If you find no problems, congratulations! You have just completed one of the most challenging mechanical operations you can do on an old car!

By | 2018-07-12T01:27:46+00:00 May 3rd, 2018|Classic Chevy Trucks|0 Comments

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