Bayonet Matching Numbers

Thursday, 18 October 2007 20:54 Last Updated on Thursday, 18 October 2007 20:54 Written by Hoboken 0 Comments

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Chevrolet Casting Numbers and RPO Codes Defined Learn All About the Identification Of Your Car

I get a lot of people looking for information about their casting numbers, and RPO codes at my blogs, so I figured that it was about time that I demystified them a bit, since I have never written an article dealing with just this issue, I hope it helps you get your questions answered.

I will discuss Chevrolet, casting numbers and RPO codes in this article, and we’ll start with Chevrolet, a Chevrolet RPO code hols a lot of vital information about your car, and along with your vin you should decode your RPO and casting identification also.

They are two totally different things, you RPO code is located on a machined pad on the engine block, just in front of the passenger head, and your casting identification is located at the back of the engine block on the driver side and top the the transmission mount.

Your casting number will tell you the engine size, what model of car it was installed in; horsepower ratings, and the transmission that was installed, some of the this are fairly basic, but it does tell you the beginning of the information on your engine.

Lets take a casting number like 3970010 this engine block when decoded could have come from a few different cars, and you’ll need to compare it to the RPO code to figure out what it is, for this article we’ll say that it came from a 1969 Z/28 camaro.

The casting identification indicates that it’s is a 302 CID engine that’s rated at 290 HP, and it was built in 1969, and it’s a four bolt main block from a late model 1969 Z/28 camaro, and this is a good starting place, it give you a good foundation to build on.

There are a few things that you need to know about the next step, and that step is to decode your RPO code to see if they match, the first things that you need to look at is the suffix code from the RPO, or the last tow or three letters, in this case the last two letters.

If your trying to determine if the engine belongs in your 1969 Z/28 camaro, the last two letter in the RPO code should be DZ, if they are any other letters, the engine does not belong to your late model 1969 Z/28 camaro.

The other thing to be aware of is that people who like to scam other people may change the RPO code to make it look like it matches a certain car, just pay close attention to the stamping, make 100% sure that it looks like the factory stamped it, if there is any doubt, have a machine shop look in to it for you.

The other two things that an RPO code will tell you, are the date that the engine was manufactured, and the plant that it was manufactured in, which should match the plant that the car was built in, if it doesn’t, it’s time to be suspicious.

I know that I have concentrated on the camaro here, but all of Chevrolet’s code on their cars work the same way, I have used a camaro because I know the most about camaros, I have studied them all though, the numbers will decode like this on any older Chevrolet.

I have decoded huge amounts of Corvettes also, and they work the same, all of the Chevrolet products, from 1965 – 1973 use the same system, I haven’t looked at the newer models, so I can’t profess to know about them, but I have done my research on 1965 - 1973 model years.

About the Author

I've been in the automotive business for about 20 or 25 years, I have worked in all facets of the industry, from parts to restoration, all different makes and models, I just want to keep people interested in the old cars because it's where my heart is.