Has anyone here installed a 403 in place of the weezing 260 in a mid '70s "X" body car? (Omega). I know of the 403's weaknesses as an all out performance engine, but I believe a quality rebuild with close to stock powerlevels in these cars would make for a peppy little runabout. It is not an Oldsmobile, but my Dad's old '76 Pontiac Ventura that he has left sitting for a while since he is retired and my mom passed away. He uses her late model Buick now. Back in the late '80s I replaced the 260 with a junkyard '77 350, just because the 260 was pathetic as far as power was concerned. I actually installed the 260 in someone's '81 Delta 88 that had a worn out deisel in it. Was a tough engine, just had no power. The 350 is worn out, (and was so even when I installed it.) If anyone has done this (it is basically a drop in) how does it perform in these cars? Being the late '70s Trans Ams had them, these cars should run about the same way with similar gearing. Car has AC, I am installing a TH350 that has been rebuilt with a Trans Go kit, and I am installing 3.23 gears as well.

 

Personal preference, but I'd find a 1968 to mid-70's 350 to build. I think you'll find more selection and availability in parts and be happier with the end results. My 2 cents worth! John

 

The 403 produces more torque than 350, a good choice. Early 350 heads with stock pistons or stock, BBO or Edelbrock heads with KB, Diamond or Arias pistons. Replace wimpy cam and add headers.

 

I have a 1968 350 on a stand to install in my '74 Cutlass if the engine ever dies, (Which it doesn't seem to want to, even with 485,000 miles), and I had considered using that. But I prefer to keep the heavier block for use in my Cutlass. I guess I could install the '68 engine in my Cutlass and rebuild the '74 engine to install in the Ventura, but it is just an easier option to install the 403 in it. Not going after a high horsepower level in the 403, just going after a little more torque, and maintaining "stock style" drivability.

 

X2 at moderate levels you'll be fine.

 

that 403 with those gears will be great in the ventura. even bone stock it'll be make a really good runner out of the ventura... i remember that a buddy's parents had a pontiac pariessien with a 403 in it, his cute little sister drove it and it was a tire shredder! it moved that big car with ease!

 

It will be a bolt in. Just everything off the 350 in there now. You will be very happy.
I,m not sure of the heads on the 350 now, but might be an improvement over the heads on the 403. Should be a bolt on.


Gene

 

My 77' 88 pace car originally had a 403, and was pretty torquey. Later put in a cam, Edelbrock Performer intake, and headers with full dual exhaust. Re-jetted the carb/dialed in the dizzy, put in 3.73 posi axle, and this thing really moved. At least until I beat on it so hard, it developed a rod knock, then built up a custom 455. Strange thing, I pulled all the rod/main caps, and the bearings looked fine. Sold the 403 a few years later to a guy that dropped it in a 70' F-85 post car, without doing anything to it. No knocking, no nothing and runs fine. Maybe just had a sticking piston pin, that loosened up over the years. Anyway he's happy with it, and doesn't run it very hard. Good luck with your project, and as mentioned. These can run pretty strong, with not that much work.

 

Thanks for the input guys. I had toyed around with the idea of putting a Pontiac 455 that I have in my spare parts shed in it, but i am not a big fan of changing engine"families" in a car, and this car came with an Olds from the factory. I can make it look stock, with stock drivability, and the car will be a fun driver. All the accessories will bolt up as well. I may even call it a 260, and then take people for a ride in it.