Solved on Sunday: Decoding cowl tags and cracking tires

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(Editor’s note: In conjunction with Road Ready Inspections, we offer this space each week so you can ask questions about your classic car or about the hobby in general. Submit your questions in the comments below and we’ll do our best to answer them! )

I have a 1967 Chevelle SS396. The other day I was looking at the cowl tag and noticed it had some “additional” numbers at the bottom. I also have about 30 books on Chevelles and they were no help “decoding” this info. Below is the cowl tag info — Mike


ST 67-13817 BF03013 BODY



25408  090021

Well Mike, how do like the Twilight Zone now?

There are few questions more baffling to classic car owners and restorers than trying to figure out cowl tags and trim tags. It’s not just GM cars but also Ford, Mopar and the like. After all, they changed tag coding year to year and even plant to plant, and sometimes over the lunch hour. It was like the wild west with each plant making up its own rules at times, subject to change at any moment.

I remember my first tour through a GM plant a jillion years ago, seemed like total chaos. Many years later I get it; it was chaos. Turns out the chaos was the auto workers trying to figure out what car they were building from the trim tags!

So since you have already read 30 books to no avail I feel I should at least get you out of your misery. And probably thousands of other guys just like you.

You have a 1967 Chevelle built in the Fremont California Plant. In 1967 somebody had the bright idea that in some plants, Fremont included, they should stamp a manifest number on the last line of the tag. But the manifest number is actually two numbers as you see a space between the two numbers. Other years and other plants do not have such numbers but they do pop up from time to time in reference to specially ordered cars.

The left number is the order number from the originating dealer.

The right number can appear in two formats — a 2-digit number followed by a space then a 3-digit number up through mid-December built cars and a single 6-digit number in cars built after that. This same number is found on the Fremont Body broadcast sheet and trim broadcast sheets.

These numbers indicate body-related option codes for that car, things such as remote mirrors and items of that nature, which is why the numbers also appeared on the build sheet. If you were to obtain the build sheet you could potentially match the codes from the tag and the build sheet.

And that’s the way it was back in the wild west. If the workers went to the bathroom the cowl tags may have changed by the time they got back! That’s why a car would show up at the retail dealer with a blue left door trim panel and red right door trim panel.

cracked tires001

I have looked at a number of cars all of which have tires that have little cracks in the sidewall. Some people say that’s age, some say they are dry rotted and the tires should be replaced even though the tread is like brand new. Do I need to replace tires that have perfect tread on them even if they have little cracks in the side? — Larry

The cool thing about being an adult is that you can do anything you want to do. Well, sort of. If you asked 100 tire store salesmen that very question I am willing to go way out on a limb and suggest every one of them will tell you that you have to replace your tires if they are cracked. To make a short story long, here is the scoop from a guy not trying to sell you something.

Should you replace tires with sidewall cracks? Not so fast, I say. (I can hear Harvey Firestone rolling over in his grave from here.)

Here is why I suggest this rationale:

First, I have bought more used tires in my life than new tires by a long shot. Call me cheap, or broke, actually both. Every single used tire I have ever bought had those same little fine sidewall cracks. The reality is that tires are far more durable and forgiving than we give them credit for.

Secondly, tires are made from layers of engineered rubber, fabric cords and metal strands all pressed together. They are layered and layered and layered and wound all together to look like a tire and create structural integrity. The sidewall of the tire is made up of the same layering of rubber, cords and metal on the inside.

What you do see from the outside is a super thin layer of aesthetic rubber layered over the structural layers and framework of the tire sidewall to make the tire look pretty instead of an industrial war zone. This thin layer of rubber has virtually zero structural integrity or capability. This thin rubber layer is marketing my friends, pure and simple. Just like the yellow on a bag of Lays Potato Chips. This layer is what makes you say, “That’s a pretty good looking tire. I will take it!”

I agree with the fact that rubber degrades and deteriorates with miles, age, ozone, abuse, the elements and burnouts. But we are talking about these fine little cracks that occur on the sidewall of every tire ever made. These are the very fine network of surface cracks that does not extend past the thin outer surface of the rubber.

Should the cracks extend deep into the tire’s cord wrapping material, the time may have come to replace the tires. What can eventually happen is that water can seep into those exterior cracks and rust and corrode the layers of fabric and metal causing them to deteriorate internally. But by that time you have worn the tread out anyway doing burnouts.

And all those used tires with sidewall cracks I have bought over the years? I wore out every single one of them until I could see air. Don’t believe me? These are my cracks on a $40 tire I bought over a year ago that I drove to work on this morning and I don’t see air yet.

P.S. You might not want to try this at home (official disclaimer required by publisher and legal department).

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