Just a curious question. As my 79 Delta 88 (Holiday88) is my first project car of my life, Hopefully more to come haha! But What Engine is better in terms of power, reliability, fuel mileage & high end improvements. I only really know the 350 olds. I never had nor know of people who have used a 403 olds before

I'm just being curious and wanting to learn

 

I've had them both. Had the 403 in a trans am and the 350 in my 442 now. Both pretty much stock, my t/a was prolly 20% faster and got better gas millage. I've heard I will have better build potential out of my 442. Just my 2cents from owning both.

 

They are pretty much the same, given the 77-79 time period. Both have windowed mains, but don't let that stop you.

The details of each are a little different, Mostly the heads, and the bore size. I would side on the 403=More cubes if you want power. Piston choice is easier on the 350,because of the bore size, you have more choices. The 403 has fewer piston sizes available, last time I checked.

If I were building a 77-79 engine I would want the one with that needed the least amount of over bore. ie, the one that needed the least amount of work.

 

My car originally came with a 403, and with a cam and other bolts on's, ran suprisingly strong. Was until a rod bearing went from having to much fun. As mentioned, probably stay with a more standard 350 or 455 though, as my car now has a 455.