Comment Classic: How To Make A ’79 Olds 403-Powered Trans Am Fly


(Every so often, a comment left at CC gets turned into a post. Here’s one by nrd515 describing how he got a 403 Olds-powered ’79 TA to run 13.35/105 in the quarter mile. If nothing else, it proves that the 403 can be made to fly)

I knew someone who got an ’81 Turbo T/A from their parents as a HS graduation present. It was disappointing, to put it mildly. I drove it a couple of times and it had no real low end at all, even if you power braked it. I didn’t want anything to do with one.

When I decided to buy a T/A, I wanted a ’77-78 due to the better looking front end, and the 400 motor, but every one I looked at was pretty much junked out. I talked to the local Olds guru, and called Mondello too, and asked about making the 403 run decently. Both of them assured me it could be done and it wouldn’t be all that much to get it into the middle 14’s, and 13’s was easily done. I bought a ’79, red without T-Tops. It had 24K miles on it, and when I got it, the converter was so plugged up the car could not spin the tires. The insane 2.41 rear sure didn’t help. I ran it at the Las Vegas Speedrome and it turned a best of 16.2.

The first thing I did was cut the converter off, and the car was able to spin the tires quite nicely. I had a custom dual exhaust made and I cracked a 15.80. Then came the Mondello plate to strengthen the windowed mains on the 403’s block (One of the dopiest ideas GM ever had), along with an intake manifold, ported to match the intake gaskets, and some mod that Mondello advised me to do to the plenum. The manifold change helped the low end a lot. Next came the $$$ stuff. First was 3.21 gears and a new carrier. Then it was ported heads, headers, a Mondello cam lifters, etc. At that point the car, if driven just right, ran it’s first 13,80 at 101, and a trip to a carb tuning guy got the car into the 13.50’s at 104 (It was super rich on the primary side, and lean on the secondaries), with launches being almost impossible unless it was driven like there was an egg under your foot until you got out about 50-60 feet.


New, bigger, tires got the car, on a cool day, to a best of 13.35@105 something. At that point, I won some money at a casino and I had 3.42 gears installed, which made the traction issue come back again and it didn’t seem to really do much else. My best was still the 13.35 I had run with the 3.42 gears. I put the 3.21 gears back in,and left the car like that until I got stupid and sold it in late 1986. It was a very good car, the only real problems were the inside left door handle broke a couple of times, and the A/C was weak.

The trans died at 50K, but I was happy it did as it had been slipping for some time anyway. Being bought used made we wonder when it would fail. The rebuilt trans had a shift kit and it would bark the tires nicely at the 1-2 shift. But the best thing was the neck snapping throttle response it had. I loved the way it drove, it had the best throttle response of any car I have ever driven. After I sold it, it sat dead for a long time, but about a year ago, I saw it driving around with the guy I sold it to behind the wheel. It will soon be painted (red), which it needed, and I intended to do, before I got “Iroc fever” and sold it.