You have just tracked down an elusive 300 in the next state that sounds just like what you’ve been looking for during the past 3 years. Price is $2,500 and from what you have been told, it is in original very good condition. You make the trip by plane, look at the car and take it for a test drive. Not bad at all, with a fresh paint job and almost new tires. The deal is made and you drive the car home.

Your 300 friends gather around the car in your driveway and you are proud as a peacock. THEN, somebody says from under your hood, “Oh ----, this is an early 383 from 2 years prior to your car being made.” It hits you like a ton of bricks that you may have been taken on this deal. You had planned on giving the engine a light overhaul anyway, but you didn’t expect this. After tearing the engine down, it appears that it may have been a quickie junkyard engine install because the original 413 was blown up or stolen. On top of this, the engine is a plain Jane, run of the mill 383. Now what?

Locating the correct engine now will be a hassle and additional cost since the seller of your dream car won’t return your calls or tells you “that is the way I got it.” Finding the correct year 413 and the proper internal organs will take time and more money.

This is one more reason our club was formed. We are here to describe what to look for and where. Should anyone want to verify a 300 that they may want to buy, go armed with information that will confirm that the car is really what it is supposed to be. Some sellers of 300s really don’t know if the car is all genuine, especially if they are the second or third owners. Some original owners may forget to tell you some important replacements made the car with non-300 parts.

The object of this article and sketches is to help you identify a 300 engine. There is no mystery involved and should help you in the purchase of your brute.

On the top of 1955 through 1958 engines, the serial number on the engine is located at center top front of the block, just in front of the valley cover, on a smooth machined area. This would be just to the rear of the water pump housing.

On the 1959 through 1965 engines, it is located on a machined boss directly to the left of the distributor, to the right of the left head and in front of the valley cover. On air conditioned cars, it will be smack under the compressor. What I have drawn is very close to the actual configuration of numbers and letters. The numbers that are drawn are not necessarily the starting number for the model year, and only used for illustration.

The 1955, 1956 and 1957 engines are stamped in a like manner except for progressive year stamping. The blocks designated for 300s were stamped with the first digit 3 to signify a prime (N) New Yorker block would be a 300 engine. “E” signified “engine.” 1958 engine stampings were changed slightly and eliminated the “E” that signified “engine”. Plus the year was first and the “3” came last. Completely reversing from the previous 3 years. The 1959 is the start of the 413 engine that is used through 1965. In relationship to later year stampings, note that it carries the complete cubic inch identification. Blocks of this year were used out of regular production and serial numbers were run consecutively with New Yorkers. (*) Two variances are recorded for 1960 as some engines are stamped with an “HP”. Whether this was done with late model year engines or shift employees at the engine factory, were of different instructions. It may be noted that the more occurring serial numbers do not have the “HP.”

Click to enlarge

As 1961 came around, again there seems to be two subtle variations. But both have the “HP” but located differently. More common placement of the “HP” is under and parallel with the R41.

For 1962, again a very small change as the “HP” follows the date of engine completion at the factory. Engine dates are the month and day the engine is completely built and does not designate the day the car was built. Engine dates will always predate body build date.

The 1963 ram engine carries for the first time, the full letter series designation as part of the engine serial number. Along with the complete month, day and year of build.

1964 ram engines were the same as 1963 but with the progression of the alphabet designation. The non-ram engines were stamped in a different way as the diagram shows. Why the “K” designation was not used in unknown, but would have been nice to separate it from any other high performance 413 in the Chrysler line.

The “L” for 1965 carried the letter “A” preceding the 41 and the question is brought up as to why the “L” could not have been used. Starting at the beginning of the alphabet was the word for 1965, but the end of the Letter Car line. Bat least it sill had the “HP” on it.

One further note on the 1955 through 1958 hemi engines. They were reheated to relieve block stress and were carefully inspected for sand holes or poor castings. These blocks were the most superior castings Chrysler made and were hand built on their marine engine line. That’s why they live so long and run so well. Almost perfection!

The 1959 and 1960 300 engines were inspected also and were prime blocks but not hand built. They did not wear as well as the previous hemis.

In 1961, Chrysler added more chrome and nickel to the blocks to help reduce the wear factor and continued this modification from this year on. The blocks were still of prime production but not the quality of the ’55 through ’58 hemis. It stands as a matter of fact.

This is why an original 300 engine is important to its owner. Originality and authenticity is what makes these 300s a true 300 Letter Car. Fake fingernails never make it for the real thing. But – if you don’t have them, a substitute is the next best thing. It’s your decision.

(*) I believe the 1959 block stamp is "MR" rather than "MP". See 1959 300E Engine Identification