The Strong Long Lasting Oldsmobile 455
Oldsmobile Rocket 455
The Oldsmobile 455 engine was produced from 1967-1976. The earlier year models had very high compression and HP output. As 1975-76 rolled around and the emission laws began to come into effect, Oldsmobile lowered the compression and HP output on the 455 engine. These “smog” motors are easily identified by the casting letter on the cylinder heads being a “J”. Olds 455’s with “J” heads are not the best HP performing Olds 455’s but there are some advantages to having one of these “smog” motors under your hood. Number one, is you can find them relatively cheap, because most Oldsmobile fans dislike the smog “J” heads they have. Even though this is not the best performing 455, it will still give any two door G-bodycar the get up and go it needs, due to the fact that they were designed to move the heavy, large 1970’s models Oldsmobile cars. They have a very long life. These smog 455’s are typically found in the 1975-76 Oldsmobile Delta and Nintey Eight. My first car was a 1987 two door Cutlass, which had an Olds 307 in it when I purchased it. Two months after I purchased the car, the 307 that was then in the car, blew a head gasket. Instead of repairing/rebuilding the 307, I simply went to several local auto salvages and was lucky enough to find a 1975 Delta 88 with 74,XXX miles on the dash and a running 455. This was a “smog” 455 with the “J” heads, but I was able to buy it for only $300, fully assembled. After towing the engine home, I removed the intake, in order to inspect the internals, before installing it. Since I had the intake already off, I went ahead and installed all new top end parts, (push rods, lifters, etc.) I reassembled the engine, installed it in the car, and fired it up. It sounded like the 307 that was in there to begin with, since the car had the original exhaust. Even though the exhaust was quiet and stock, after driving the car out on the highway, I could quickly tell this was not the orignal 307. The car had a far sharper acceleration and the top end speed was improved also, pegging the 85 mph speed odometer needle. Over the next two years following me installing that 455 in my first Cutlass, I did here and there performance modifications, such as aluminum intake, MSD ignition, Holley carb, headers (and in case you’ve never tried finding a set of headers for an Olds 455 in a G-body car, let me tell you, it’s not easy or cheap), and I also added a true dual 3″ Flowmaster exhaust to the car. As far as the 455 itself, I rebuilt/replaced the entire top end, including the cylinder heads, but never did any bottom end work. The pistons and entire rotating assembly were stock and original. Believe me, after those simple bolt on performance parts, that 455 no longer ran, nor sounded like a smog 455. That engine was so healthy and ran so good, it ended up destroying the stock tranny in the car, which resulted in me having a custom TH-4OO tranny built. Installing the 400 transmission involved as much modifying as the headers did, as I had to shorten the drive shaft, build a custom cross member, and yoke. The good news is, after all that hard work, time, and money I invested in this car, I drove it for a total of 10 years, before selling it. This 455 was manufactured in 1975, I bought it in 1998, and drove it daily until selling it in 2008, which means that “smog” 455 ran for a total of 33 years, with the original, stock bottom end, as I never had to repalce it. That’s proof of how durable and long lasting these smog 455 Oldsmobile engines are. Who knows, the gentleman I sold the car to a year ago is probably still driving it today, with the same engine! Never underestimate an Olds 455!