Early Chevrolet Tech Tips

Tech Tips for early Chevrolets

Thermostat

You should really always use a 180 thermostat.
Engineers have figured out in the last few decades that the ideal operating temperature for any street engine is just below 180 and up to 200 degrees, for best fuel/air-mix burn and to get least cylinder wall wear.
Especially when doing short runs in the colder and wetter months, you want the engine temp to come up as quickly as possible and be sufficiently high and stay up long enough to burn off the water vapor and unburnt fuel in your crankcase.
Of course you could just change your oil every 1000 miles, but it will last much longer and your engine is happier, with more heat.

You also want to pressurize your system to have fewer and smaller bubbles forming around the cylinder walls, which don't help with heat exchange.
A 7 lbs. radiator cap is safe with the original copper/brass radiators. The higher the pressure, the higher the boiling point and less bubbles.

You can check the temp gauge with a cooking thermometer, after carefully removing the radiator cap, next time you are at temperature.
You can also check your thermostat in hot water on the stove with the same thermometer.
Some thermostats can be bad straight out of the box when new. It is supposed to just barely crack open, at the temp that is stamped at the bottom of the copper bulb.
Thermostats work best without drilling any holes into them. They actually all have a tiny bleed hole, its just hard to see.
In a dark room with a single light source, you can see it, right at the edge of the moving center piece.

Gear Oil

Only use GL-4 rated gear oil in your synchro-mesh transmission.

Avoid GL-5 gear oil. It has twice the amount of sulfur/phosphorous additive, which will slowly peel off the surface of the brass parts.
You can confirm this, when you drain GL-5 oil after some use and the oil looks like thick metallic copper paint in direct sunlight.

GL-4 rated gear oil is a little harder to find these days. NAPA stores have it.

I also use this for my rear end, although GL-5 would be alright, since there are no yellow metal parts.

Transmission and differential oil should be changed annually, especially in colder and damper climate zones.

Coolant

Use a 50/50 mix of antifreeze and distilled water for winter temperatures that go below freezing.

For climate zones that have winter around and above freezing point, use distilled water and Redline Watter Wetter.

It is a surfactant (lowers the surface tension of a liquid) allowing better contact with the metal of the cooling system and helping with heat transfer. It also includes a rust preventative and lubes the pump bearings.
Surfactants find application in detergents as well and before this product, some have used a little laundry or dishwasher detergent in the coolant for the same effect.
I use it together with distilled water in both my rides, because in the winter it never gets below freezing in my garage overnight. And the coolant never gets anywhere close to boiling.
Water has the best heat transfer properties and together with water wetter it gives the most cooling effect.

Block and Head internal descaling

Professional cooling system de-scaling is done with Sulphamic acid for hard water, lime and antifreeze build up. Oxalic acid is used to remove rust.
Sulphamic acid crystals are available at the hardware store in form of 'grout and tile cleaner'.
Oxalic acid crystals are available in form of 'wood bleach'.
Containers say what acid is used and its pure acid crystals with no other additives.
Available in 16oz. containers, which gives the right mixing ratio with water for the typical car cooling system with 3-4 gallons capacity.

Properly diluted, both acids are just as mild and safe as vinegar (acetic acid) and citric acid, but are more effective and cost is the same.
These treatments are safe to use with copper/brass radiators.
It is supposed to be safe with aluminum radiators as well, but I would do some tests first to determine how much reaction time is actually safe.

Oxalic acid used to be sold as a heavy duty 2-part cooling system cleaner over the counter until a few years ago. Recommendation said to do this annually...

For best results it's essential to keep temperature at engine operating temp and to keep the flow going.
Instructions are to drain and flush first, then fill with the diluted acid mix and run the engine at fast idle for 3 hours.
Do one acid treatment at a time, starting with the sulphamic acid, then drain and flush, followed by oxalic acid, then drain and flush.
The final step is to neutralize any remaining acid with a mix of washing soda and water and run the engine again for a while, then drain and flush and finally fill with coolant, but using distilled water instead of tap water, this time.

These methods really work exceptionally well.
I did both, back to back, on my old engine that had serious scale and rust build up.
Before the treatments and despite a new 3 core radiator, coolant temps easily climbed above 180 during the hot summer months with harder use.
After the treatments, the same engine now needs the thermostat to even get up to 180 degrees, even in the summer.

General Rust and Scale removal

I have used the electrolytic method many times and it works well, but is limited to the rusted areas that are directly exposed to the sacrificial steel.

I also like Oxalic Acid crystals to remove rust, especially for areas hard to reach.
Hardware stores carry it in pure form as 'Wood Bleach' in 12oz containers.
Mix 3-4oz per gallon of water.
'Barkeeper's friend' is mostly fine abrasives with only a small amount of those crystals.

Oxalic acid is still considered a mild acid, but more effective against rust, than vinegar, molasses or citric acid. It's also mild enough to be safe with softer metals, like brass, copper, etc.
You can accelerate the rust removal process with heat and agitation.
Keep the acid hot and stir the rusted parts around in the acid or keep flowing the acid around the parts.

Works excellent for descaling and rust-removal of coolant passages and radiators and was available over the counter until a few years ago, for just that purpose, offered by Prestone.

For smaller parts and when I need instant results, I use Muriatic Acid (Concrete or Pool cleaner), also available in hardware stores. Its 30% diluted HCL, which is aggressive and will eat metal if exposed too long.
Be very careful when using HCL ! Even with this diluted concentration, take all safety precautions for working with harmful chemicals and ONLY work outside, as just the fumes alone will corrode bare metal in its vicinity.

White Wall tire cleaning

Westley’s Bleehe White does not contain bleach.
They just use a word that sounds like it but spells differently.
Some marketing genius came up with that one, apparently not having a clue what real bleach does to rubber.

I use it on both white and black wall tires, maybe once a year.
The whitewalls get wiped down once a month with an old cotton t-shirt and a little water.

If you can, avoid abrasives, like medium or hard brushes, steel wool, etc. on new smooth rubber.

Brake fluid and cleaning shoes

Brake fluid is hygroscopic, meaning it attracts and retains moisture.
Making it necessary to bleed the brakes on a regular basis and to not store brake fluid for a length of time, once the original seal is broken.

Water alone doesn't dissolve brake fluid.
That's why you need a detergent when washing it off your hands.

Boiling in water with detergent gets even very badly soaked linings as dry as they can be.
The detergent lifts the brake fluid and the boiling water flushes it out.
It's a very safe method, doesn't cost anything and works.

I once had a leaking wheel cylinder with new brake shoes, I just installed.
Took them off and boiled them in water with dish washer detergent for 1/2 hour and it worked. They were like new again and didn't grab.

I've had very good experience with my closed torque tube drive shafts and 3.55 rear gears for both my rides.
One has a hopped up late 235 and the other a hopped up and .060 bored out 261.
My 261 makes almost 250 lbs of torque and both have the stock 3 speeds, axles and drum brakes, that never failed me.
The 3.55 rear without overdrive gets both engines around peak torque at freeway speeds and mileage is around 20 mpg.
With torque tubes I like that they don't twist or stress the rear leaf springs like open drive lines do, sometimes requiring additional mods to stock springs on cars with a higher torque motor.

I don't race my rides but have driven both every day for over 20 years now.
They have always kept up easy in everyday city and freeway traffic, including Los Angeles rush hours, when I lived there for 8 years.
My 1/2 ton truck with the 235 was fully loaded countless times and never complained even at steep grades at freeway speeds, driving for hours at a time.

1940s chevy car and truck drivelines are a lot tougher than they sometimes are getting credit for nowadays.
Can't tell you how long they will last for racing on the track or against kids on the street, but for everyday normal driving they are apparently more than adequate.
Gotta love those old chevs and how well they were made originally. Lasting until today and beyond, especially with periodic care and respect they deserve

For freeway/high speeds, you want to select the transmission and rear gearing to run the engine around peak torque for best performance and mileage. Connect a vacuum gauge to find out if the engine is lugging.
A 261 with stock cam gives peak torque around 2000 rpm and will work very well with an overdrive and 3.90- 4.11 rear gears, giving good performance and mileage on level ground.
A mild built 261 with an RV cam has peak torque around 3000 rpm, adding more power/torque and making it a lot easier on freeways with steeper grades, especially when pulling a trailer or driving a loaded truck. At those rpm it doesn't break a sweat and could even go almost twice the rpm with a little more carburetion and would still last for a long time.

When you add the poor aero dynamics of the trucks into the mix, it helps to have a stronger motor with a slightly higher power band.
My truck with a better breathing 235 and 261 cam does quiet well and runs forever at 2500-3000 rpm, even during long hot desert trips.
It was about 35 years since the block was rebuilt and the compression on each cylinder is still around 95% within spec. after a valve job

Patrick's introduced a 3.55 ring and pinion replacement kit, decades ago, for the earlier torque tube drivelines.
It's the only way to convert the 47-55 trucks rear gears without any cutting or welding and you can keep your 3 speed as well.
I have them in my daily driver since 2000 now with my 235 and its great around town and on the freeways, at 18-20 mpg.

You can drain the tranny and expose the u-joint and than do this...

Jack one wheel off the ground.
Turn the wheel 2 complete turns.
- Count the turns on the drive shaft.

3.55 turns on the drive shaft equals a rear ratio of 1:3.55

Cars ratios:
49-52 stick ... 4.11
53 stick ... 3.70
50-54 PG ... 3.55

I have KYB Gas-a-just shocks on the rear of my daily 52 chevy 1/2 ton truck, for many years.
These are a combination of hydraulic and nitrogen gas shocks.
Easy and gentle cushion under light load, but gets increasingly firmer with heavier loads or movements.
I also removed the smallest leaf of the springs and have 2" lowering blocks.
Rides smooth around town, firmer on the freeways and can handle rough dirt roads, regardless if I am fully loaded, partially or have an empty bed.
They adjust to anything and were cheap, too.

I'm very happy with my front pair of Durant monoleafs.
They are on my daily chevy 52 truck with a 650 lbs. cast iron 6, since 2004.
I also got special designed gas shocks for the dropped 3", also with lifetime warranty and made in USA.
- Keep the original tapered spring shims for correct camber and improved cornering and handling.

They get a good work out every day, and I drive freeways, city and deep dirt roads and never once bottomed out in all those years.
They give this old truck a much softer ride than leaf springs and haven't sagged in all those years.
I remember talking to James Durant over the phone at the time I got them, to hear what he thinks about safety of monoleaf springs. He came across very open, honest, knowledgeable and confident.
Durant Enterprises
P.O. Box 7278, Dept. CT
Newport Beach, CA 92658
(949) 673-5625

2x 216 carbs for a street/freeway 235/261, especially with dual exhaust headers.
2x 235 carbs for engines with a bigger cam and above 3500 rpm.
3x 216 would be even better in that case.

I had the Carter W-1s on my 235 for many years and thousands of miles and really like them.
I find them as easy to rebuilt as the Strombergs. Especially if you have good instructions, which are simple enough.

The 14-22 Strombergs, with the stock .058 jets, give a very good fuel mix and delivery whatever rpm range and accelerate perfectly getting max power from my 261 engine at all times. They do seem to match very well the flow of my bored 261. The same jet size may not work as well on a 235.
The mechanical parts move so smooth, you actually never really feel there are carbs between your pedal and the engine. And I like the fast idle function for starting on colder mornings.

I also once had a pair of NOS 235 Carter YFs on my 235, before I switched to the W-1 carbs.
Those felt a bit more advanced than the W-1, but were designed 10 years later.
I think 2x 235 carbs on a street 235/261 engine that never goes over 3000 rpm are just too big, even after rejetting. The venturi size needs to match the airflow from the engine. A pair of 216 YFs would be better, but the neoprene accelerator pump can be troublesome with ethanol blended fuel.
Both Carter W-1 and Stromberg bxov carbs use leather and don't have problems with alcohol in the gasoline.

These carbs are fairly simple single barrels with little involved in a basic rebuilt.
Instructions are usually included in the kits, but the only ones that are really needed are the float adjustment measurements and an exploded view of the whole carb and it's parts.

I remember the Carter W-1 required an obsolete measuring aid when setting up, which I found inside an original kit from the period. But it can be done accurately without it, as well.
The 1942 - 1947 Chevrolet Shop Manual has several pages of step-by-step instructions and more for the Carter W-1.

The Stromberg bxov was really straight forward for a basic rebuilt.
In the repair kit, the cardboard sleeve around the leather piece helps to transfer and slide the plunger inside the bore. Don't slide it off before the plunger is in place.
And like with any old used carb, if the throttle plate shafts are worn and leak, they probably need new bushings.
Other than that, both carbs and repair kits should match perfectly.

When setting up and balancing them with the linkage, I found what works best is using a vacuum gauge and a motorcycle carb synchronizer/balancer with dial.
The slightest adjustment makes a big difference and getting both carbs absolutely perfect in sync gives best engine performance.
Also with dual exhaust, make the pipes equal length before the mufflers, for a real smooth running engine.

With the blending of Ethanol into Gasoline, it may be necessary to adjust the carbs to work best.

The W-1 has a mechanical metering rod and adjusting fuel/air mix is easily done by just replacing the rod, accessible on top of the fuel bowl cover.
I always wanted to experiment with different metering rods, because the standard size is not ideal when using two 216 carburetors on a 235.
Then I got lucky and found an old collection of various metering rod sizes, very cheaply.

The standard metering rod size was 67-46 for the W-1 574s model with .093" main jet.
These numbers, stamped into the rod, represent the tapered diameter of the rod going from .067" at idle and part throttle to .046" at WOT.

In my collection of metering rods I found a pair of 66-50 size.
That seemed just what I was looking for, as I needed a slightly richer mix for off-idle and city driving but a leaner condition at wider open throttle when accelerating.

I did a test run and the engine not only ran smoother, but also had more power and really noticeable quicker acceleration.
It was much more responsive when pushing into the pedal, compared to before.
I could also accelerate much easier now going up a relatively steep hill on my street, at WOT starting from 1st gear.
I did a short freeway run as well and both hard acceleration and driving at higher rpm and higher speed was also improved, with a slightly higher vacuum gauge reading.

If other metering rod sizes aren't available, one could drill out the main jet to .094" or maybe .095" and keep using the standard rod.

If the ethanol blend keeps increasing in the future, I will have to do that as well and probably also lower the float level a little.

I did a few more experiments with separating the ethanol and also comparing with the original metering rods.
There was a noticeable difference in power whenever I drove the richer metering rods, with or without ethanol.
Checking the spark plugs shows no difference.

I learned a couple of things from this:
I can increase power by changing the metering rods.
As the ethanol blend keeps increasing in the future, I will be prepared.
Removing the ethanol drops the octane level by about 2-3 points.
Engine runs smoother without ethanol, regardless of metering rod size.

The casting date code of the heads is only visible when removing the valve cover, next to the temp sender.
It uses the same letters and numbers code as the casting date code on the block by the starter.
You can see how the date was stamped on a plaque that was updated each casting day, held in place by two screws.

The code on the passenger side is not a date code.
Every head in that location shows the letter B. The following two digits are not related to the casting date.

Delta cams in WA has reground my original 261 cam with more lift and duration. It's their RV cam grind.
I really like their cam grind patterns, which are quiet different from the vintage type grinds that had asymmetrical duration for intake and exhaust and a lot of overlap, giving good HP at high rpm, but less torque than the stock cam for the street.
Delta 254 adv. dur. grind is symmetrical with very little overlap, giving higher than stock torque up to 3000 rpm, yet still has good HP at higher rpm.
They also have a slightly asymmetrical 254/264 grind with even less overlap, which adds another 5 HP at high rpm. It's their popular 'Bullldog' grind, also distributed by Patrick's and Tom Langdon

1953-55 corvette and trucks starting in 1956 all used the same 261 cam.
Cars starting in 1954 had a hydraulic version of that cam with very similar specs.

You can hook up a vacuum gauge and adjust the idle mix screw for highest vacuum.
You basically want to set the screw until the engine runs with the least vibrations.

Timing adjustment needs to be more advanced these days, because our fuel has more octane than back in the 50s. At sea level you probably get best timing around 5-7 degrees.

The vacuum advance port with a carb designed for these engines is just above the throttle plate at idle, so you don't have to disconnect it for timing at idle as it will have zero vacuum anyway.
When you rev the engine, you can make sure it works, as the distributor starts to rotate CCW (advance) with increasing rpm.

You may not have the original flywheel that came with the engine.
Some flywheels have timing marks at 5 degrees before and after top dead center.
Some have a ball embedded, others a circle punched into the surface. That indicates TDC.
Start setting at 5 degrees advance (ball or circle is about 1/2" to the left of the pointer) and drive around to get a feel.
Then keep advancing in small increments until you start hearing slight pinging with wide open throttle at a slight incline and at low rpm, like the bottom of a moderate hill.
Back off (retard) timing again until the ping disappears and little further.

Reading spark plugs works best, when shutting the engine off and going in neutral while you are driving down a road.
If you idle the engine for a while and then look at the plugs, it will have carbon all over them and you don't get an accurate reading under load and driving condition.

Here is how I understand timing, compression ratio and fuel octane, which are all closely related:

You always want the most complete burn that is possible with your compression ratio, doesn't matter what engine.

The higher the octane rating, the SLOWER the gas/air mix will burn.
Has nothing to do with the gas having more energy.
Octane is an additive, usually mixed in right at the pump, according to your selection, using the same gasoline from one large tank.

Slower burn is helpful with a higher compression ratio, where you need to advance timing and start the flame earlier, to prevent pre-ignition which can happen when the compressed gas/air mix gets so hot that it self-ignites ('explodes' instead of burning at the proper rate while it expands and pushes the cylinder down)
Too much advance timing is not good, as the flame starts to early and has too much expansion before the piston gets to TDC and in the worse case burns a whole into the surface, if left in that condition.

Unless you modified your engine to have higher than 9.0 compression ratio, you will not need more than 87 octane.

You always want to run the LOWEST octane your engine can allow for the most complete burn.
This gives you best performance, as in power and mileage.

Using too high octane than needed for a complete burn, is simply wasting unburnt gas into the exhaust.

One could explain all this a lot more elaborate and with a lot more detail, but this is always how I thought of it in relatively simple terms and easier to explain.

If you don't know the CR of your engine, start with the lowest octane gas and set your timing to give the slightest ping at the bottom of a moderate incline in highest gear and WOT.
Keep track of your mileage and note how much power you get.
Then try higher octane gas and compare, always advancing the timing for slightest ping with every change in octane rating.

Without oxygen sensors, this is how you can tune for the best timing and gas.

Of course, always read the spark plugs and adjust for your kind of driving and use.

In most countries (including all of Europe and Australia and NZ) the minimum rating at the pump is shown as RON, which is higher than in the US where it is shown as the average of MON and RON.

RON: Research Octane Number = running fuel in a test engine without load

MON: Motor Octane Number = running fuel in a test engine under load

Bypass filters were introduced when detergent oil became available.
They do a very good job trapping even the smallest particles of the entire oil in just a few minutes.
Full flow filters can not be too fine, so they don't lose pressure.

A combination of both type filters is used by big rigs these days.
The full flow filter protects the main moving parts of the engine from larger particles and the bypass filter keeps the oil clean and extends oil drain intervals.

Interesting side note: Todays Wix/Napa Gold full flow filters are more efficient with a lower nominal particle rating, than standard bypass canister filters still available today.
However there are also bypass filters available that have an extremely low nominal micron rating.

The additional oil line was installed originally when later heads and rockers were used on earlier blocks to allow more oil to the top.
Later blocks had a larger metering orifice to the top and later rockers were redesigned to retain the increased oil and pressure.
Sometimes with an old and plugged up engine that didn't pump enough oil to the top any more, this additional line was installed as a fix.

I have used one of the 1000W external tank type heaters in my truck a few years ago.
They work best when connected to the water drain outlet, at the lowest point of the block. The heater should be installed just below the block. The other end with the warmer water should enter at the head before the thermostat, not at the water pump, or it will act like a permanent radiator bypass during the warmer months. Also keep the car/truck heater valve closed until you drive, so all the warmed water enters the head only.
A check valve at the heater inlet also prevents a bypass situation in the other direction, when the engine runs.

Cold water from the bottom of the block enters the heater and the thermostat switch opens around 110° so it doesn't generate bubbles. The warm water blocked by the inlet check valve expands and raises up the hose that goes into the top of the engine, forcing colder water at the bottom of the block back into the tank, when the switch closes and the whole cycle begins again.

It works well to warm up the coolant to a warm temperature within a couple of hours.
It does not help to warm up the oil in the pan however, which could be done with a warming pad.
Magnetic ones can fall off, as magnets lose strength at high heat over time.
High-temp adhesives may give better results.

I removed the tank eventually and believe the block heaters at the freeze plugs work better without maintenance. The tank requires occasional removal and thorough flushing from debris, accumulating at the bottom of the block and ending up in the tank, making it less efficient over time or blocking it in older engines.

These days, I just use a small heater that I slide under the engine.
It never drops below 30° inside my garage and this also helps warming the intake on my straight 6.