It is easy to put an older-style valve cover on a new-style engine because the rocker assembly bolts are in the same place. It is not recommended, however, because they tended to leak more. If you want to preserve the shape of the holes, be sure to add reinforcements.
Engine Condition
The project engine for this book was completely unknown to me. It was sitting in a garage, all taken apart in boxes. I had no idea where each specific lifter was located when it was running nor the condition of the engine. This was good for documenting because you can’t take anything for granted.
In your case, you might have a good reason for rebuilding it. One good indication that an engine needs a rebuild is excessive blow-by. This is obvious by the amount of visible smoke that comes out of the valve cover cap. There shouldn’t be any. This could be valve adjustment, worn piston rings, or worn cylinders. Another obvious sign of wear is low oil pressure at idle.
Compression Testing
If you have a desire to know the overall health of your engine, a good place to start is with checking the compression. A few things contribute to low compression, such as piston ring wear and valve issues. Purchase a compression gauge kit. It will come with all the connectors and fittings that you need. The following is a quick procedure that works well.
The side cover is much shorter, starting below the spark plugs, than in previous years. This is a better design. Chevrolet made many subtle changes between 1938 and 1962.
With the ignition switch off, remove all the spark plugs and the distributor cap. Prop the throttle wide open to get the most accurate reading. Screw the fitting into the number-1 spark plug hole until the rubber O-ring squashes just a bit. Turn the engine over (with the starter) long enough for the compression gauge to register the compression number of the cylinder. Keep cranking until the gauge needle stops rising. This is important. Record the number, release the gauge’s pressure (small pushbutton on the gauge), and do it again to make sure it’s reading very close. Do this on every cylinder, one at a time.
They need to be within 5 percent of one another. Any numbers above 95 psi means that the engine is okay and will run well. Compression as low as 65 psi should be okay but may smoke and idle poorly. With a new engine, they are in the 130 range.
The tall-cap distributor has a taller cap and a taller internal shaft. Also, the rotor is taller, so those parts are not interchangeable with the pre-1953 distributors.
On the 261 engine I recently worked on, the measurements were number-1, 140; number-2, 137; number-3, 138; number-4, 137; number-5, 137; and number-6, 138.
Flywheel Identification
The flywheel is something you don’t automatically think of as a big deal; however, these engines are in the transition years, so be careful. Chevrolet introduced the 12-volt system in 1955. Prior to 1955, everything was 6 volts. Why this matters is because the 6-volt starter had a different gear pattern, and the flywheel had 134 teeth on the 6-volt starter version while the 12-volt version of the same flywheel has 168 teeth.
To add to the confusion, the starter gears both have the same number of teeth, but the pitch is different. I am really talking about the flywheels’ ring gear; however, unless you want to remove and replace a ring gear, the difference is insignificant. Be sure to count the teeth on the flywheel so you know which starter to purchase.
The flywheel’s ring gear is the issue here. It is relatively easy with heat to remove a ring gear, but finding a replacement is the problem. Most of us just replace the entire flywheel when necessary. Don’t skip over the fact that you can turn the ring gear around to get fresh gear meat for the starter.
Due to the concern of unwanted combustion, make sure the ignition is off or the distributor cap is removed before attempting anything that requires removal of a spark plug. Safety first always!
Even if someone has upgraded your vehicle to 12 volts, it may still use a 6-volt starter. I prefer the 6-volt starter because to carry double the current of 12 volts, the windings are beefier. You won’t hurt a 6-volt starter if you use it for the normal short periods of time it was designed for.
Is It a Rebuild Candidate?
Here I am talking about the quality of the engine candidate. Is it worth the considerable expense to rebuild? Do you see visible cracks in the water jacket or anywhere else? Do you have any documentation that would lead you to understand the cylinder bore size that was done at the last rebuild?
The best years for Stovebolts are 1958–1962. Think of Chevrolet as a company with technology that is constantly evolving. The Holy Grail of Stovebolts is the 1958–1962 261 engine. It is the same physical size as the 235 with about 40 more horsepower due to its larger displacement. It also has native full-flow oil filtering. Keep in mind that any Stovebolt after 1953 is considered the best 6-cylinder engine for that vintage. Another major factor is engine wear. You do not want to purchase an engine that is bored .060 over because it is reaching the end of its life. You also do not want to purchase an engine with cracks or casting issues. ■
Sometimes the piston has a number stamped on the top face of it. You discover something very important when you remove the head of an unknown engine. You should wire brush away the carbon and dirt from the center of the top of the piston. A number such as .010, .020, .030, etc., stamped on the piston, tells you the last cylinder bore size. If it reads .060, you are getting very close to the last bore size that is available for these cylinders. This may be a prohibitive factor for you because it costs just as much to do the first overbore as it does to do the last.
Organization Is Key
The engine for this specific rebuild has hydraulic lifters. I like that, even knowing that an argument could be made that they cost horsepower because the engine is very quiet and runs very smoothly without much adjustment. In the box of engine parts, I found the 12 lifters for this project. Three of them are missing the retainer springs and the caps, and there is stuff all over the bottom of the box.
A compression tester costs about $25 at your local tool store, and it is well worth it so you know you have good compression. In the United States, the inside scale is used because you are reading PSI.
Because hydraulic lifters are expensive, I’d like to save them. After a little research, I learned that I could take them to a machine shop and have them surfaced so that they run against the cam as good as new. I will not use them if the machine shop expert recommends that I buy new ones.
Since I am doing a complete rebuild and do not care about the current timing of the engine, I removed the head, distributor, plug wires, spark plugs, coil, road tube, starter, generator or alternator, water pump, carburetor, intake and exhaust manifold, valve cover, and lifter side cover. I organized these subsystems carefully, keeping the hardware separate. I separated the hardware, putting things in labeled bags. And the fun soon begins!
CHAPTER 2
TOOLS AND ENGINE CLEANING