Oldsmobile V-8 Engines 1964–1990: How to Rebuild: How to Rebuild

INTRODUCTION

It’s a common misconception that an engine overhaul is beyond the capability of the average do-it-yourself (DIY) mechanic. Sure, it’s an exacting process. Sure, it’s time-consuming. But you can do it if you take your time and thoroughly study each step of the process. It helps if you’re a detail-oriented person. If you’re not detail oriented, this is your chance to learn!

It is important to be meticulous when cleaning, measuring, and reassembling the engine. Don’t rush any part of the overhaul. Leave yourself plenty of time. Hurrying the process can lead to forgetting to tighten a bolt or to installing a piston ring upside down. Seemingly small mistakes like this can have serious consequences.

My approach in writing this book considers that decades have passed since the last Oldsmobile V-8 engine was built. Many readers, I assume, are Oldsmobile enthusiasts who are intent on restoring their collector cars. Then, there are some who just want to breathe new life into their tired old friend. In either case, engine inspections are likely to reveal extensive wear on many components. The information in this book will help to identify the extent of the wear and present overhaul options for the cost-conscious rebuilder as well as the spare-no-expense restorer.

Many tasks in this book can be carried out in more than one way. I always present the best method. In some cases, alternative methods can be used that have advantages, such as being quicker or not requiring a special tool. In these cases, I document the alternative method(s) as well. All methods that I discuss are safe and follow accepted shop practices.

CHAPTER 1

GENERATION II OLDSMOBILE V-8 ENGINES

The second-generation Oldsmobile V-8 engine began production in 1964, and it represented a significant upgrade over the original Rocket design. Offering reduced weight, greater efficiency, and improved power potential, the updated engine helped improve car sales. Oldsmobile’s popularity rocketed through the 1970s, and the brand regularly achieved sales of 1 million cars per year through the 1980s. The legendary durability of the venerable Oldsmobile V-8 was undoubtedly a big part of this success.

This book covers second-generation Oldsmobile V-8 engines installed in vehicles from 1964 through 1990. These engines were available in displacements of 260, 307, 330, 350, 400, 403, 425, and 455 ci. They were used in nearly all V-8-engined Oldsmobiles through the 1970s.

The Oldsmobile V-8 was also used by other General Motors (GM) automotive divisions and even in GMC motorhomes of the 1970s. If you go waterskiing, you might even see an Oldsmobile engine in a jet boat, as Oldsmobile engines became popular in certain marine applications.

Enthusiasm for Oldsmobile V-8 engines remains strong, even decades after the last example was manufactured. With millions having been produced, these durable powerplants are destined to be popular for decades yet to come.

Regardless of the year of manufacture, all Oldsmobile V-8 engines have this unique bypass tube/hose attached to the thermostat housing. If the engine does not have this bypass tube, it is not an Oldsmobile engine.

Engine Identification

When installed in a vehicle, an Oldsmobile V-8 engine can be immediately distinguished from engines of other manufacturers. Look for the bypass tube and hose attached to the thermostat housing at the front of the engine, just below the upper radiator hose. Only Oldsmobile engines have this hose/tube.

The 1976-and-earlier engines have 10 nuts securing the valve covers (bottom). Later models have only 5 nuts/bolts (top), although you can still see the ears where the other 5 bolts would have gone.

Another quick identification trick is to look at how many nuts or bolts secure the valve covers. On 1976-and-earlier models, 10 fasteners secure each valve cover. On later engines, there are only 5.

Although Oldsmobile engines tend to look similar, there are many subtle differences that are critical in terms of finding the correct internal parts. Fortunately, Oldsmobile provided an easy way to identify the specifics of its engines. On every Oldsmobile-manufactured engine, there is a number cast into the block at the top front, just below the bypass tube. This number identifies the engine displacement and the year of manufacture.

Just forward of the thermostat housing is a number cast into the engine that can be used to identify the displacement.

GM Corporate Use

Oldsmobile engines were used in more than just Oldsmobiles. In addition to their primary use in Oldsmobile cars, Oldsmobile engines were used by every GM division at some point or another. With the exception of Chevrolet, the Oldsmobile engine endured longer than engines from other GM divisions.

Not only were Oldsmobile engines installed in cars from other GM divisions but also engines from other GM divisions were sometimes installed in Oldsmobiles at the factory. In particular, the Chevrolet small-block (305) and Pontiac 301 were commonly installed in Oldsmobile cars in the 1980s.

During this time, GM commonly (and confusingly) referred to the Chevrolet 305, Pontiac 301, and Oldsmobile 307 generically as 5.0 liter engines. There is very little that these three separate engine designs have in common other than their approximate metric displacement. If in doubt, look for the bypass hose/tube shown earlier to be sure that you have an Oldsmobile engine in your Oldsmobile!

VIN Identification

The engine can sometimes be identified by referencing the vehicle identification number (VIN). The VIN is found in one of two places, depending on the year of manufacture. If you have a 1967-or-earlier vehicle, a VIN plate is in the front doorjamb and is visible when the driver’s door is open. For 1968-and-later vehicles, a VIN plate is visible through the windshield at the base of the dash on the driver’s side.

GM VIN numbers were in different formats over the years. All 1981-and-later models use a standardized 17-digit VIN. The eighth digit identifies the engine and the tenth digit identifies the model year. Prior to 1981, GM VINs were not as standardized and took multiple formats over time.

On 1971-and-earlier models, the VIN does not include information related to engine identification. On these models, there is a data plate riveted on the firewall on the driver’s side of the engine compartment. The information on this plate only identifies whether a V-8 or a 6-cylinder engine was installed at the factory. No specifics about the engine are provided.

On 1972–1980 models, a 13-digit VIN code was provided. On these models, the fifth digit identifies the engine type and the sixth digit identifies the model year.

On 1971-and-earlier GM cars, the VIN does not indicate the type of engine installed in the vehicle. A body code plate like this is attached to the firewall. The plate does not provide much detail as to the engine installed but can identify whether the car was originally equipped with a V-8 or a 6-cylinder engine.

VIN Derivative on the Engine Block

The 1968-and-later Oldsmobile engines also have a small-font number stamped into a machined pad near the front of the engine, just below the cylinder head on the driver’s side of the engine. This number begins with a three-digit code. The first digit is the division code:

1 = Chevrolet

2 = Pontiac

3 = Oldsmobile

4 = Buick

6 = Cadillac

Note that the division code identifies the car line in which the engine was installed, not the engine type. As we know, Oldsmobile engines were installed in vehicles from all GM divisions, so any of these numbers is possible.

The second digit identifies the year of manufacture. On 1979-and-earlier models, this is the last digit of the year of manufacture (9 = 1969, 0 = 1970, 1 = 1971, etc.). On 1980-and-later models, a letter is used instead of a number (A = 1980, B = 1981, etc.). The third digit is a letter code that identifies where the engine was manufactured.

The VIN derivative number uniquely identifies a particular engine to its chassis. It is stamped into a machined pad just below the cylinder head on the driver’s side of the engine. The last six digits of this number should match the last six digits of the VIN.

The six numbers that follow the three-digit code should match the last six numbers of the VIN (known as the sequence number). If the last six numbers of the VIN match these six numbers, it means the engine is the same one that was originally installed at the factory. In other words, it’s the numbers-matching engine for the car.

Engine Family Identification

Second-generation Oldsmobile engines can be divided into two major categories: small-block and big-block. Small-block and big-block engines share a fundamentally similar design where some parts will interchange between small-blocks and big-blocks. Here’s how it breaks down in terms of engine displacement:

Small-block: 260, 307, 330, 350, 403

Big-block: 400, 425, 455

Keep in mind that these categories are about the design of the engines, not necessarily the engine displacement. This explains the odd phenomenon whereby a 400 is a big-block, but a 403 is a small-block.

Parts Interchangeability

Generally speaking, there is wide parts interchangeability within the engine families (i.e., parts from small-block engines interchange with other small-block engines and parts from big-block engines interchange with other big-blocks). However, parts interchange between engine families is more limited. For example, crankshafts, connecting rods, and intake manifolds will generally not interchange between small-block and big-block engines.

That being said, many parts do interchange between engine families, such as camshafts, rocker arms, exhaust manifolds, distributors, water pumps, and fuel pumps. Small-block owners are often happy to discover that cylinder heads from big-block engines will swap onto small-block engines without much effort and will generally result in a performance gain.

One very special note is that many 1965–1967 camshafts and lifters do not interchange with 1968-and-later camshafts and lifters. The earlier and later engine blocks have a different lifter bore angle. This has confounded many an unaware Oldsmobile engine builder!

The internet is awash with information regarding parts swapping among engines to achieve greater strength and performance. If you’re building a budget performance engine, do some further research. However, most Oldsmobile engines are gone from the junkyards, and people selling used high-performance parts are usually aware of their value.

If you’re thinking about purchasing used parts, consult with an automotive machine shop to make sure the parts will be worth using, especially after the necessary machine work is carried out. There is a huge variety of new parts now available for Oldsmobile engines at reasonable prices. It’s usually best to go with new, high-quality parts versus taking chances on parts that are now decades old.

What Is an Overhaul?

Overhauling an engine means restoring the internal parts to new-engine specifications. At minimum, an overhaul involves replacing the piston rings and reconditioning the cylinder bores (honing or reboring). If the cylinders are rebored, new pistons need to be installed. The main and connecting rod bearings also need to be replaced. If there is any damage to the crankshaft bearing journals, the crankshaft will be reground, requiring oversize bearings to be installed.

The cylinder heads will also receive close attention. The sealing surfaces of the valves and seats will be resurfaced and valve oil seals replaced. The valve guides, springs, retainers, and seals are inspected and replaced as needed. The camshaft and valvetrain components—rocker arms, pushrods, and lifters—are carefully inspected.

At the time of overhaul, it’s also wise to replace the water pump, distributor, alternator, and starter. The goal is to have everything under the hood fresh and ready to deliver many years of trouble-free service.

When Is an Overhaul Necessary?

There are no hard-and-fast rules as to mileage before an overhaul is needed. An Oldsmobile engine that has been driven normally, had regular oil changes, and not overheated can achieve 200,000 miles before an overhaul is needed. Conversely, a car that has been neglected or seriously overheated can fail very early in its life. Diagnosis is needed to determine the condition of the engine. Diagnosis is covered in Chapter 3.

Overheating is the most common cause of early engine failure. For this reason, it’s essential to replace cooling system components at the time of overhaul to be sure that the new engine will last. Always replace the cooling system hoses, water pump, and thermostat. Have the radiator serviced or simply replace it with a new one.

Before starting the overhaul, read through this book and become familiar with the requirements and scope of the process. An engine overhaul is relatively straightforward with the correct tools and equipment; however, the job is time consuming. Even if you think the overhaul will be a simple one, plan on the vehicle being down for several weeks. Overhauls almost always take longer than planned, as there will be unforeseen delays involved with scheduling machine work and obtaining parts.

Alternatives to a Full Overhaul

Sometimes the inspection and reconditioning of original parts is not the best way to go due to the cost of parts, machine work, and time. If the engine block, heads, and crankshaft are in reasonably good shape, an overhaul can be done at low cost. However, if a major component is badly worn or damaged, the job can be much more costly and time consuming. In such cases, consider other options.

Rotating Assembly

Engine parts suppliers frequently sell reconditioned kits that include a reground crankshaft, connecting rods, pistons, bearings, and rings. The kit will be ready to install and may also include the gaskets and seals needed to reassemble the engine block. Some machine work on the block will still be necessary, such as a cylinder rebore, align-honing the main bearing journals, and resurfacing the cylinder head gasket surface (commonly known as decking).

Short-Block

A short-block is a complete engine block assembly, including the crankshaft, pistons, connecting rods, bearings, rings, camshaft, oil pump, timing chain, and seals. Your existing cylinder heads and valvetrain can be bolted into place, assuming that those parts are in good condition.

Used Oldsmobile engines are still available at some wrecking yards. While they offer a quick and inexpensive solution, you’re usually guessing as to the condition of internal components. Also, there are many small variations among engines of different years and models, providing potential headaches that are hard to foresee.

Long-Block

Long-blocks are basically short-blocks with new or rebuilt cylinder heads installed. Long-blocks will have the valvetrain components installed and correctly adjusted. If you purchase a long-block, all you will need to do is install the engine covers and external components. Long-blocks also frequently have warranties, which is another good reason to go this route.

Used Engine

Salvage yards frequently have used engines available and will sometimes provide a brief warranty so that you can verify whether the engine runs normally after installation in your vehicle. A significant amount of time and money can be saved by choosing a used engine, but there is a risk of major engine problems arising in a short time.

If possible, try to find an engine that can be inspected before removal from the vehicle. That way, you can verify the mileage and the condition of fluids and possibly hear and see how it runs before it’s pulled from the vehicle. Also, if the vehicle has been wrecked, it’s a clue that the engine was running prior to the wreck and is more likely to be in good condition.

CHAPTER 2

TOOLS, EQUIPMENT, AND SUPPLIES

An engine overhaul requires a significant investment in tools and equipment. Some items can be rented or borrowed, but hundreds of dollars can be spent on renting by the time the job is complete. This chapter will help you understand the tools of the trade, as access to these tools will be part of what determines the level of work that can be done on your own.

The tools and equipment that are purchased should reflect your future plans and interest in an engine overhaul. If this will be your only engine overhaul and/or you are on a budget, just get the basics and borrow or rent the rest. If you’re interested in learning more about engine overhaul and possibly doing another in the future, you might want to buy some items that aren’t essential but that you might reuse.

Get a pair of safety glasses and leave them on whenever you’re at work. Most eye injuries happen when they are least expected. A dust mask should be used whenever there’s debris in the air, such as when cleaning parts.

When it comes to hand tools that will receive heavy use, make sure that they are good quality, made of forged steel, and come from a reputable manufacturer. It isn’t necessary to buy the best of the best, but also don’t get bargain-basement quality. You will be sorry.

WorkArea

You don’t need a full workshop or even a garage to carry out an overhaul, but a workspace is essential. This area must be organized, safe, and clean. It is best if the work area is indoors, but a sheltered outdoor area can work if there is an indoor area available to store parts.

Storage

A disassembled engine takes up more space than you might expect. Be sure to have plenty of shelf space to store the parts—preferably not the closet! Parts taken out of an old engine are very dirty, and they shouldn’t be stored in a living space. Cabinets with plastic drawers are available inexpensively, but cardboard boxes