Can you decipher these codes?

March 1, 2009 | By Richard Prince


I have a 1955 Chevy Bel Air 2-door sedan with what I have been told is a 350 cid 290-horsepower crate motor. The codes on the passenger side of the block read as follows: imo615 and below those are 4vp. The first letter of this code could be either a number 1 or the letter “L”. Also, the 3rd letter could be the number zero or the letter “O”.

Can you tell me what this motor is and some specs if you do know? The car has a 3.07:1 ratio or so 9” Ford rear end and it runs fairly good now.

I am considering putting a different cam in it along with a lower rear gear ratio, something in the 3.50 to 3.89 range. I want to know what lift cam I could put in without making any fatal contact within the motor. I don’t want anything too radical, just some more “rump, rump” and more power.

The engine has an Edelbrock manifold and carburetor that I don’t think would need changing with a slightly more powerful cam.


I am very familiar with Chevrolet engine codes and the numbers and letters you’ve provided make no sense to me. The important codes you should look for include the block casting number, which is most likely on the rear, upper driver side of the block adjacent to the flange area that the transmission bell housing bolts to. The block also has a casting date and this is usually found on the rear, upper passenger side of the block adjacent to the bell housing mount area with earlier engines and on the side of the block on the passenger side with later model engines.

If the engine left the assembly plant as a complete or partial assembly, it normally has assorted information, including the assembly date, assembly plant, displacement and horsepower rating, stamped into the machined pad that’s just forward of the passenger side cylinder head. If the block was sold all by itself with no internal parts then this area normally will be blank.

Having said all this, it really wouldn’t be all that useful to know the original size, horsepower, date of assembly, and application of your engine because there is no way to know from the dates and codes whether any of that information still applies. Your engine may very well have been rebuilt and/or modified many times over since it was originally built. The only way to know for sure what size it is, what compression ratio it has, what horsepower it makes, what the cam profile is and so on, is to actually measure everything yourself.

It is impossible for me to tell you what cam will or won’t function in your engine without knowing a lot more about what’s presently inside the engine.

You want to install a hotter cam but what’s hotter depends on what’s in there now. You can remove the existing cam and take it to an engine builder who has the machine to measure it. Based on what comes out, the builder or any of the major cam manufacturers can recommend a replacement.