Tech Tips

We Welcome Any and All Tech Tips to Help Fellow Early Bird Drivers

What's Missing From Your Oil May Be Destroying Your Engine

from CASCO's ThunderEnlightening newsletter

What is ZDDP? There seems to be a problem with the oil you are probably using in your T-bird. An oil additive known as ZDDP (zinc dialkyl dithio phosphate) has been gradually removed from commercially available engine oils.

There are two main reasons for the diminishing use of ZDDP in our oils: First, the EPA has required new-car auto makers to guarantee that catalytic converters will last 100,000miles. The use of ZDDP is hard on catalytic converters. Second, cars that have roller rocker assemblies do not need ZDDP.

What does ZDDP do for our engines? ZDDP is a surface modifier. It modifies bearing to journal surface characteristics to prevent metal-to-metal contact. Under the right conditions of heat and pressure, it plates over the contact surface and provides a sacrificial coating. As it breaks down, it dissipates into the oil where it remains in suspension until the right conditions are again met and the process stars over. This cycle reduces the possibility of scuffing and galling.

We have spoken to our cam supplier and they agree that currently available oils are different, and they would suggest using an additive that replaces the missing ZDDP. We have reviewed the available products and have settled on a product called ZDDPlus, a concentrated four-ounce bottle that you simply add at every oil change. It is recommended for all engines built before 1988 that have flat tappet setups. We have added this to our product offering as Part No. Z4, which sells for $10.85 for a four-ounce bottle. For information: www.classictbird.com.

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Is Your T-Bird Really Locked?

Try this one on your Little Bird: Lock your door from the outside and then push hard a number of times on the outside door-handle button. Many of you will find that by doing this, your door-lock button will slowly work its way upward until the door is no longer locked.

All T-Birders should know that it is very easy to over-tighten the lock buttons and to do so may allow the situation described above. This is not a problem of inaccurate reproduction parts. Our Birds came from the factory this way. The problem is that when the lock button is screwed onto the shaft too far, it limits the available downward travel of the shaft. The result is that the lock mechanism inside the door-latch assembly is not able to fully engage.

The good news is the fix is simple. Just unscrew the lock button a few turns to allow the shaft a bit more travel. --CASCO ThunderEnlightening.

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T-Bird Handling Issues

Maybe you’ve noticed that your T-Bird doesn’t handle the way it did once upon a time. There can be a lot of reasons and here are a few comments on why:

As a result of wear caused by use and neglect, your car may develop looseness in the steering assembly. Some of that “slack” may be found in the drag link and the tie-rod portion of this critical part of your car. If your Bird is equipped with power steering, you should expect 1/8-inch of slack in the control valve when the engine is not running. When the engine is running, this will not be evident because the energized control valve and steering ram cylinder adjust for this travel.A greater amount of slack can usually be attributed to worn tie-rod ends, steering boxes, idler arms and rarely, ball joints.

But don’t replace the ball joints on your Bird just because they may be 50-plus years old. They almost never wear out and just may be the best ball joints ever used on any type of automobile. The very same parts were used on cars made by the Checker Motor Corp. from the mid-’50s through the end of production. Even the Yellow Cabs couldn’t wear them out. I have only seen two bad examples in my long experience with the Birds. It is possible that these particular joints were never greased, thus causing premature failure. If your car’s ball joints have ever been serviced they are probably still fine. Look elsewhere for worn out parts.

Front-end alignment, or the lack of it, makes a huge difference in the handling and drivability of your car. Tire choice will determine how your T-Bird should be aligned. Toe-in should be set at zero inches for radial tires. Bias- ply tires should have toe-in set at about 1/8 to 3/16 of an inch. Radial tires are the single best improvement I ever made on my Thunderbirds. I have been using Michelin X tires since 1962. I recommend the 205 size on all three model years.

Now looking at the other end of the car for answers: A common handling problem is caused by loose U-bolts that fasten the axle housing to the leaf-spring stack. You may notice telltale symptoms of this condition when the car darts in one direction upon acceleration and then heads in the opposite direction when braking hard. These U-bolts must be very tight. When you check them, or attempt to tighten them, don’t use an impact wrench. There is a lot of rubber in this assembly that will absorb the energy supplied by the wrench and the nuts won’t tighten the way you have seen nuts tighten in other applications. I use a 3-foot-long cheater bar, take them up to about 75-ft-lbs and apply it evenly. When you do, you may break a sweat.

The above is by no means an exhaustive list of the causes for handling problems in your T-Bird or any other car. However, these are some common causes. You might get lucky and find one or more of the above hints to be just what you needed to get your Bird back on track.

-- by the late Walt Nuckels, a highly regarded T-Bird expert, from the Rose City Thunderbird Club’s Bird Watcher newsletter, January 2002

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