Project Geronimo: Evaluating A Vintage Engine – What Do We Do Now?

Our beat up old workhorse pickup is the type of vehicle that any car lover can afford at practically any auction or salvage yard around the country. The goal is to keep Project Geronimo on a tight budget but spend “smart money” on upgrades that will make the truck a very cool daily driver that is both dependable, and safe.

Our 1960 Chevy pickup was purchased with the stock 235 cubic-inch Blue Flame engine. Known as a pretty dependable work engine back in the day, these old stovebolts were not as efficient as the mules today – but they got the job done.

Our secondary goal is to take this three-quarter ton Chevy truck from 1960 and make it outperform a three-quarter ton truck from 2016. The only area where our worn out, straight-six, three-on-the-tree truck could approach the performance levels of newer trucks is on gas mileage.

In 1960, this three-quarter ton C20 235 cubic-inch pickup was rated at 11 miles per gallon, and in 2016, the same 3/4-ton was rated at 11-13 miles per gallon. If we make smart modifications on a shoestring budget, and get 13 mpg or better, our goal will have been achieved.

The Engine: A Historical Overview

The first thing we wanted to evaluate in the pursuit of our overall goal of creating a daily driver, was  the vintage truck’s engine. The old “Blue Flame” engine didn’t necessarily need to be rebuilt to specs, but we needed a strong platform to work from. And, by the way, the Blue Flame reference was used by GM in its marketing efforts starting in 1941, because a blue flame in the cylinder meant better combustion than a yellow flame. That scientific marketing research was conducted before the Internet, so you know that it is true.

The Chevy 235, inline six-cylinder engine was originally introduced in 1941 for large trucks and is known as one of the truly great Chevy engines due to its power and durability. By 1950, the 235 was reduced to full-sized automobiles and smaller pickup trucks. The first Corvettes produced from 1953 through 1955 were equipped with the 235 Chevy, and the engine continued to be a staple as versions were used in GM and Chevy trucks until 1962.

The 235i Blue Flame was the workhorse of GM for several years. Later, inline six engines were developed with better fuel distribution and equalized cylinder workload, but these 235’s were as dependable as any engine created.

By 1960, the 235i “Thriftmaster” inline-six was relegated to base engine status with a solid lifter version for pickup trucks with standard transmissions and a hydraulic lifter version for trucks and passenger cars with automatic transmissions. For trucks, a downdraft carbureted model with a Rochester single barrel carb, and a lesser used model with an updraft Carter carb were available with the 235ci engine.

The 235 Blue Flame was replaced in 1963 with the third generation 230ci Chevrolet inline six, at which time the aging 235 was dropped from production after a 21-year manufacturing run.

What We Are Trying To Figure Out

Our base evaluation needs to take a solid look at what we have to work with. If it doesn’t seem that the engine is stable enough to become a dependable daily driver, we need to determine if it can be rebuilt, and if it is worth the cost to rebuild it. If not, then we need to examine the replacement options. Ultimately, a good engine assessment will determine which option is the best return for your investment. That is where the “smart money” spending comes into play.

We started by doing some basic checks. Taking a look at the fluids is a great first step. Start by checking the oil for metal flakes, sludge, water, or anything else out of the normal. Pull the dipstick out and check for oil at the end of the stick. Make sure the level is correct, the color looks clear and not too dark, and there are no metal shavings in the oil. Metal shavings are a sure sign that there is metal-to-metal contact and parts are wearing. This will eventually lead to catastrophic engine failure.

Start by checking the fluid levels. Take a good look at the quality of the fluids. Does the engine oil have metal particles? Is the coolant clear and in good condition or rusty?

Now is a good time to also inspect the engine for oil leaks. There will probably be a lot of road grime and crud built up in areas around the block, but you can tell an oil leak by the fresh layer of oil on top of the crud. Many times these leaks are caused by bad gaskets, but a closer inspection should reveal if there is a bigger problem. While we are on the subject of oil, check the air filter for oil and make sure it is filled to the line.

Next, look at the coolant in the radiator and check for rusty sludge, clarity, and coolant level. Check the water pump for leaks, test the radiator cap, and check the radiator for any obvious damage. The water hoses and thermostat housing should be given a look over to see if there are any leaks or damage prior to starting the engine.

We were a little shocked to see a huge damaged section in the radiator where a fan blade probably gouged the core. The epoxy repair was pretty handy but was not as effective or dependable as we would like.

In the case of our old engine, we were shocked to find a big gash where a fan blade had hit the core and the previous owner had repaired the damage with epoxy. JB Weld works wonders, but we are going to eventually need this replaced. Water pumps for these old beasts are about $30 off-the-shelf at O’Reillys, and well worth the time to replace when we change the radiator. Add a couple of $10 hoses and a thermostat and we’ll be into the cooling system for about $300. A bargain price to keep an engine working correctly. A cool engine is a happy engine.

The rest of the cooling system looked like it could use some refreshening as well. The hoses were soft and spongy, the water pump looked very aged and the thermostat housing appeared to have experienced some leakage in the past.

We saw that the fan belt was old and probably needed replacing, along with some wiring and fuel line. A new fuel filter is always a safe choice. Overall, we didn’t see any fuel leaks around the pump or lines, but the carburetor did look like it was worn where the shafts go through the body. There were some tell-tale signs of a little fuel escaping past the throttle shaft and it looked like the top gasket was leaking. This is common in older engines with the stock carb.

A quick look around the engine at the wiring, determined it is pretty exposed on these older chassis. Then finally, we checked the engine mounts to ensure they would hold the engine in place when we attempted to start it.

Cranking It Over

We primed the carburetor by filling the fuel line from the pump to the carb, then did a quick check of the timing by turning the engine over until the white dot on the flywheel lined up with the pointer, checking where the distributor rotor was pointing. Everything appeared to be correct, so we sprayed a brief shot of starter fluid in the carburetor and pulled the choke cable.

A quick twist of the key and the truck came to life after a turn or two of the crankshaft. Nursing the throttle, the old engine sounded fine with no noticeable banging or internal noises. Unfortunately, Chevrolet did not use many gauges in these work trucks, which did little to tell us what the oil pressure or RPM was. We did know that the lights were working because they lit up when we turned the key to the ACC position. At least we knew that there was oil pressure.

The stock instrument panel leaves a lot to be desired. There is a working speedometer, a fuel gauge that doesn’t work, an engine temperature gauge that does work (but we don’t know how well), and two idiot lights.

Slowly the water temperature gauge (the only other gauge besides the speedometer) began to register water temperature increase. This let us know that the truck was warm enough to open the choke and start taking a closer look at what we were dealing with.

The engine’s idle was roaming from somewhere near 1,500 rpm to a low near 450 rpm, where it would stumble and rise back to the 1,500 rpm range before repeating the cycle over and over. This is a sure sign of a vacuum leak. As the engine rpm would cycle through it’s peaks and valleys, we detected puffs of black smoke exiting the exhaust.

The color of exhaust smoke can tell you a lot. For example, white smoke from the tailpipe indicates coolant and water in the combustion chamber, and is usually caused by a blown head gasket. Blue smoke is burnt engine oil, and indicates that oil has seeped past one of the sealing surfaces inside the engine. Both of these problems need to be addressed right away before really bad problems happen.

The optional oil filter was in place, which is a good sign, meaning that the engine had a small measure of protection against dirt and debris carried through the lubrication system. Not all early engines had an oil filter, so this was a bonus.

Black smoke means that your engine is running rich — too much fuel, or too little air in the air-to-fuel mixture. This generally doesn’t require you to rebuild your engine, but you will have to adjust or repair the items controlling the fuel/air mixture. In this case, the carburetor.

Where We Stand Now

All the initial indicators seem pretty good for our vintage Blue Flame. Other than a vacuum problem and rich fuel mixture, we probably won’t have to do too much to make this old beast dependable as a daily driver. There is an oil leak at the rear main, which is pretty common with the rope type seals. There is almost no way to change the rear main rope seal while the engine is in the vehicle and have success in stopping the oil leak — so for the time being, the leak can stay until the next engine overhaul.

We attempted to adjust the fuel mixture, without success, on the single barrel Carter YH carb. The options we are left with include attempting to rebuild the carburetor, replacing the carb with a new one, or finding an EFI option. This is a subject for another article where we can discuss the best long-term economic value.

We took a good look for leaks on both sides of the engine. The rear main seal showed signs of a leak, but that is to be expected with these engines. The rest was normal grime and slight leakage over years.

The vacuum problem was identified as a leak at the distributor. The vacuum measured at the intake was 22 inches of mercury (inHg), which led us to the other end of the system at the distributor. The leak was exacerbated by the ancient vacuum advance system with the stock distributor, which was probably the original unit that came with the vehicle in 1960, so the wear was significant. Replacing the distributor will happen sooner rather than later.

Using A Vacuum Gauge To Check The Engine

We tested our engine by hooking up a vacuum gauge with a piece of tubing to the vacuum port on the carburetor. Once the engine was warmed up to operating temperature, we checked to make sure the engine still had sufficient oil pressure. Then we checked the vacuum gauge. Typically, you are hoping to see 17 to 22 inHg, however our engine was pulling between 15 to 24 inHg as the engine chased around the idle.

This gave us hope that the engine was not going to need a major rebuild but might need some cylinder head work. As mentioned before, a vacuum leak at the distributor was detected. We removed the T-fitting and blocked off the vacuum line to the distributor and our vacuum read a consistent 22 inHg. This high vacuum level and steady reading told us that the engine was sound. Low vacuum usually indicates bad piston rings or poor camshaft/valve timing.

We were stunned by the great vacuum numbers this old engine was able to pull.

We goosed the throttle quickly to see if the vacuum would drop, then rise past the 22 inHg mark before settling back to the 22 inHg normal reading. This let us know that the rings and valves were fine and working perfectly. If the vacuum drops to zero, then only rises to the normal operating pressure, the rings are probably worn.

The vacuum reading should go three to four inches of mercury above the normal vacuum reading before settling to the original starting point. Vacuum measurement that bounces up and down can indicate a sticky valve, burnt valve or worn valve guides, and the engine should be disassembled to discover the source of the problem.

Our Plan

Our immediate goal is to rectify our ignition problems and vacuum leak by replacing the distributor and other ignition components. An HEI distributor replacement is a smart and economical choice for this type of project as it offers a neat and compact package that includes electronic ignition instead of the breaker points, and a built in coil. The newer HEI units offer plenty of electrical power compared to the original HEI units, plus they clean up the engine bay because all of the components are self contained. No more ballast resistors, ignition coils bolted on to the cylinder head, and no coil wire to worry about.

We know that somewhere down the road a swap to an alternator system will probably happen. We want modern charging ability and dependability in this project. Spending money on an alternator system is “smart money.”

After we get the distributor replaced, we will take more readings on the engine to determine if we need to change the carburetor. We already know that our cooling system needs updated and we will probably be changing out the old generator charging system in favor of a one-wire alternator. Another solid and dependable upgrade that will help turn this beater into a trusted daily driver.

After running the engine to normal operating temperature, then shutting the vehicle off, we saw the reliability of the JB Weld radiator repair performed by the previous owner.

About the author

Bobby Kimbrough

Bobby grew up in the heart of Illinois, becoming an avid dirt track race fan which has developed into a life long passion. Taking a break from the Midwest dirt tracks to fight evil doers in the world, he completed a full 21 year career in the Marine Corps.
Read My Articles

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