More on the Olds 403 engine

July 1, 2012 | By Richard Prince


I read the comment you made about not using the Olds 403 block because it overheats. The story is not completely true, only the 403 put in the California built Trans Ams had this problem, not any of the other cars using that motor. That means the problem did not come from the block.

But even if you do not recommend the 403, wouldn’t it make more sense to tell the reader to maybe purchase a 350 Olds or even a 400, 425 or 455 Olds instead of telling him to get a Chevy small block and put that in the Omega? The 350 Olds is a far more superior motor than the 350 Chevy engine. And it will last forever if built correctly. Just the higher nickel content makes the block lighter and stronger.

I really have a hard time with the idea of always putting the 350 Chevy in everything that has four wheels. That is not car craft in my book. That is just going the easy way and makes the car craft hobby boring. I also would not put a 350 Olds in a Camaro. I think the engine brand should be true to the car brand.


I don’t have any personal experience with the Olds 403 cid engine but there is no shortage of information out there about its propensity to overheat. I found nothing to support your assertion that the overheating tendency was limited to California-built Trans Ams.

The most likely cause of the overheating problem is the block’s Siamese cylinder design. The absence of water jackets between the cylinders inhibits the ability of the cooling system to do its job. Since the 403 blocks used in California-built Trans-Ams were essentially the same as the 403 blocks used in other GM vehicles it’s not logical that the problem would be limited to these cars only.

I also don’t understand why you believe that a 350 Olds engine is “far superior” to a 350 Chevy engine. They are both excellent engines and absent lots of hard, accurate data that demonstrates why one or the other is superior I wouldn’t claim that it is. Even if you are correct that the Olds block has a higher nickel content that doesn’t make it superior. While the addition of more nickel may favorably alter cast iron’s qualities I don’t think that makes it lighter as you state. I say this because nickel is actually heavier than iron (nickel’s atomic weight is 58.6934 while iron’s is 55.845), so more nickel and less iron will actually result in a heavier block.

With all due respect, your opinion that the engine brand should match the brand of car it’s going into is just that, your opinion. Mixing and matching different car makes with different brand engines has been a common practice for more than half a century. And, of course, the practice has certainly not been limited to engines, with countless rear ends, transmissions, body trim parts, suspension setups, and just about every other bit getting swapped around. Of course, just because something has been done for a long time doesn’t make it right, but in this case there really is no “right.” Or wrong. The whole point of the old car hobby for most of us is to enjoy it and for a great many people mixing parts from different car brands adds to their enjoyment, so why not accept that?