(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.
Single best mod for an Olds 403 is a set of 68-71 350 heads for the compression boost.
Yep, I was told they would be hard to find, but I found them the same day at S.N.A.P (Southern Nevada Auto Parts). They needed some refurbishing, and a friend’s uncle ported them and installed the biggest valves that would fit.
single best mod for an olds 403 is to wrap it in a GMC motorhome
Reading this just makes me want a 1978 Olds Custom Cruiser with 403 power. 🙂
Yes, this reminds me of two cars: My wife’s 1977 Olds Delta 88 and oddly, my Quad 4 powered Pontiac Sunfire GT. With the Sunfire it’s the same formula, a big Olds engine in a sexy Pontiac body.
Doing quarter mile runs and pushing a 403 like that for any length of time it’s damn sure gonna fly alright……..
Into pieces.
Pablum.
Calling it pablum is pablum.
Describe in detail your bad experiences with the Olds 403. Be specific.
I’m not saying the 403 is bad.
It was as good as many of the mid 70’s maxed out small block motors for it’s purpose but like a 400 Ford and other oddballs from that era, but,,, it’s a bad choice for a reliable HIGH performance engine unless you spend $$$$$$$$ to build it.
Take a mid 70’s factory Pontiac 400 and a Olds 403 and abuse them, run a bunch of quarter miles, redline them,,, work em HARD until something gives and the 403 will be the first to go.
That’s all i’m saying and i’m not wrong.
In other words: you have no facts whatsoever and are bloviating. Thought so. I will take Joe Mondello”s word over yours.
A 403 is no different that any other Olds, with one exception: it breathes better than anything but a 455 due to the large bore.
“A 403 is no different that any other Olds, with one exception: it breathes better than anything but a 455 due to the large bore”.
Bore size effects breathing,,,,,,, the 403 is NO different,,,,, got ya’.
Now i know who i’m talking to.
We’re done.
Actually, yeah, it does: the larger bore unshrouds the valves. (That’s why it’s so hard to build a strong Chevy 305.)
No need to run away, though.
As already stated, the 403 isn’t really fundamentally much different from any other Olds V8. That said, it does have two so called “weaknesses”, the windowed mains, and siamesed bores. The windowed mains can be reinforced through a girdle though.
That said, the 400 Ford really can’t be compared to the 403 in that respect. The 400 Ford doesn’t have any fundamental design issues that prevent it from being a high-performance engine. In fact, it is basically just a stroked 351C with a taller deck height. The issue with the 400 Ford is that it had low compression and excessive deck height clearances in stock form. That said, like Mondello for Oldsmobile, Tim Meyer is the guru for Ford 335 series engines (351C, 400, 351M), and he offers decent pistons for this engine. A simple piston swap with a decent cam, and a 400 Ford can make 400 hp with stock heads. TMeyer has build many of these engines into very high horsepower engines, some strokers in the 600 hp range. And the 400 Ford has been very successful in the Engine Masters challenging, winning several years in a row.
I always wondered about the 403s potential in the Firebirds, any source for these cars tends to basically gush about the legendary 400 and outright ignore the 403 despite similar ratings, as well as being more likely engine to find depending on year and transmission. I really never knew it’s strengths and weaknesses at all. 13.35 at 105 is fast, I too like the 77-78 nose more but a non T-top/non “Bandit” Trans am that puts down those kinds of numbers sounds like my Ideal F body, even with the duckbill 79 front end
Is the Mondello plate a girdle for the mains?
Mondello offers a full girdle, as well as “straps” that reinforce each individual main cap.
ETs and trap speeds like that are impressive, particularly from an engine that was not known for it’s performance potential when new. I think it’s cool that you worked on making the 403 perform instead of taking the easy way out and bolting in a 455.
That’s about the same performance I got from a well sorted out V-8 Vega, and it was pretty much useless as an everyday driver. It sure didn’t have AC!
I’m betting you surprised a few folks at stoplights. Most guys back then looked to see if the shaker scoop had a “TA 6.6” decal or a “6.6 litre” decal. The TA was the hot one that got some respect, and the 6.6 litre was considered easy meat.
I love a good sleeper!
My Dad bought a pair of matching blue TA 6.6 Decals from the Pontiac dealer to install on his in place of the 6.6 litre ones back in the day, apparently he got some mean stares at the parts department!
I actually looked for a 455, and the ones I found that were in running condition were high mile engines and I didn’t want to have to put out all the money needed to rebuild one at one time. That’s why I did the 403. I had a good time killing 400 motored T/As at stoplights. I always wanted to put slicks on it and maybe a bigger cam to see if I could get into the 12’s, but 13.35 was damn good, and more then enough to get me into trouble several times. That car, especially with the OE tires, was a treacherous bastard in the rain.
Car Craft magazine did a build up of a 403/Bird in their November ’79 issue, which I still have. Their best time was 13.78 @ 103.21 with the stock but re-jetted Q-Jet.
I need to look that article up. What cam did they use? The Mondello cam was really good and I went with it because the local Olds guy recommended it, and he dally drove a 12 second Cutlass that was a real sleeper had the next “lumpier” one that Mondello made.
They used a Crane cam from H O, p/n HC-97, and real W-30 heads
I’m sure a modern cam (Mondello has a drop in roller conversion) would be a better choice.
Thinking about this has me wishing I had the $$$ to do this all over again. The T/A was the only car I’ve ever regretted selling. My present 2010 Challenger runs almost exactly the same E.T at the same MPH, but it doesn’t have any kind of throttle response compared to the T/A. It’s superior in every other way, but I still miss that car.
I don’t have any decent pics of the T/A at all, but this is the closest I could find. Mine was “chickenless”:
Interesting build idea & full points for actually doing it.
I had to look up the 403 windowed mains, I’d never heard of that before. I’m just scratching my head as to why they’d do that in the first place, because it makes the casting cores more complex. Less weight? More room for splashing oil to fly around?
Just goes to show with enough ingenuity and application of cubic money almost anything can be made to fly.
Yes, less weight. All the automakers were on a diet at the time the 403 arrived.
It was primarily done to reduce weight. Olds was trying to shed pounds in the late 70’s and even used aluminium hoods on some cars (Delta 88 for example). The windowed mains were used on all Olds engines pushrod V8 from 1977 on, including the 350 (except diesel) and 307. These weaker blocks are obviously less desirable for high performance.
Excellent results, thats plenty fast enough for a daily driver. I remember a guy showing me his T/A back around 1980 and being a little embarrased it had the 403-even then the engine had a stigma
Here in California, just about all the Trans-Am’s and Formula 400’s had Olds 403 power from 77 on. The 403 is an interesting engine, technically a small block Olds based on deck height. It was a very oversquare engine, lightweight for it’s displacement. I heard all the jazz back in the day about the 403 being weak and not suitable for high performance applications, but I can’t say I ever saw many of them fail. The 403 eventually replaced all the larger Pontiac, Buick, and Olds V-8’s and became GM’s defacto ‘big block’, much as the aforementioned Ford 400 had become. Pretty common in B, C, and Pontiac F bodies ’77-’79. There was a rumor that some ’77 403’s were built with a ‘heavy duty’ non-windowed block, but I have never seen one.
I wonder if anyone has ever stroked these by offset grinding the crank & using chevy rods? The 330 cranks were forged, probably the one to use.
You could turn down the mains on a late 400 or a 455 crank…they used a 4.25″ stroke. With a 403’s big bore, that would make for over 500ci.
Love the article. The 403 T/A has to be understood to be loved, and I love them. I find it odd that so many decry the 403 for its windowed mains when that really doesn’t come into play at all under about 5500rpm.
“How do I make my 403 T/A faster?”…I read this all the time on forums.
The 403 T/A was horribly handicapped from the factory with the de-tuning. I had a 1977 Z28 with an auto and a 3.42 gear and would walk away from my room-mate and his 79 T/A 403 with a 2.41.
Without ever touching the internals of the 403 they can be made very decent running street cars. Swap to a 3.42 gear, remove the restrictive exhaust and replace with long tube headers with true duals, tuned carb as mist Q-Jets were horrible from the factory IMO, remove unwanted emissions if you can.
As well, re-curving or addition of a high performance distributor. One has to remember that when these cars came out we had no 91 or 93 octane gas, and the timing was de-tuned to deal with it.
Great article. I can read anything I want about a W72 trailer queen which takes well over $20k to purchase, not much written about the T/A 403 mule that most of us common folk can afford.
Really, WHEN I buy mine, these changes will be made immediately.
Well I had a 403 in my t/a and it ran Low 11’s…First of all i got another motor in a junk yard and I brought new pistons, shot peened the rods for extra strength and everything was weighted and balanced .I had block bored 30 over and actually bigger bore size than a stock 455. The crank was turned 10/10 whatever that means.I had the deck shaved and the head were shaved and fully port and polished with the holly dominator intake port matched to the heads and the felpro gaskets.I ended up with 10.5 to 1 compression ratio. I use a 286/292 split duration comp cam.Tried holly and other carbs but used the quadjet tricked out very responsive. Installed an electric pump after breaking every manual pump i used at high rpm’s.Tried a 200r4 didn’t hold up 350 was junk. So I got a turbo 400 with a 3500 stall convertor had to get the drive shaft shortened. Put a posi unit in with 373 gears and tractions bars so it would hook up. Last but not lease I had a sprint car driver show me a trick of rubber grommets in the distributor to keep it from advancing to much and detonating and burning pistons after replacing 3.
i forgot the exhaust 3 inch tube hooker headers with a cross over wastegate installed and dynaflow mufflers
Doug D
If you look very carefully at your photo you can see that even if that block was not windowed a solid section would not be very thick at all. Just millimetres thick between the bores at the thinnest, a little more elsewhere. This appears to be due to the need to give enough clearance for the large diameter pistons operating in that big bore.
If you are going to really turn it up and have lots of rpm then either a girdle tying into the pan rails or a complete lower crankcase (like a Cadillac Northstar or a Porsche 928 V8) is a must. Do one of those.
An interesting “what if” alternative mentioned to me, although I have not seen it in an Oldsmobile V8 engine, is to machine the crankcase out to accept a variant of the “tunnel crank” arrangement (the conventional tunnel crank set up is used by Tatra, Maybach and the like). In this case something more like the “barrel crankcase” version used by Offenhauser would seem to the be the approach to follow.
A regular Oldsmobile crankshaft could be used with the discs capturing the main journals. The discs do not need to be uniformly thick all 360 degrees round. The entire assembly would be dropped into the block. It would need a “sub-frame” assembly to trap it and bolt it into to the rest of the block, probably bolted through the pan rails for a start.
Lots of work, this one. Still, it would be very rigid and strong if done with a bit of thought. Exotic!
I had a new 1979 Trans Am with the 403 Oldsmobile engine back when they came out and considering the other performance cars offered at that time, it wasn’t that bad; however not great. You’re right about not being able to spin the tires off the line and with the rear gear, it would shift out of first gear at 55 mph.
Made a few modifications to improve the performance horsepower:
1. Opened up the shaker hood scoop (cut out the back plastic and molded in screen.
2. Re-jet the carburetor.
3. Advanced the distributor timing.
4. Installed a true dual exhaust and removed the GM convertors. Replaced them with convertors for a Dodge.
5. B&M shift kit in the transmission.
When the speed shop completed the work, they ran it on a dyno and it produced 185 hp to the rear tires. I thought that was pretty good considering the horsepower rating to the flywheel was only 185.
Today, I have been looking for a really good condition 1979 10th Anniversary and I found one with the 403 engine. Would really like to have the 400 Pontiac engine with the 4-speed; however the wife may want to drive it occasionally.
Living in CA, not sure what I will be able to get away with; however I plan to pull the engine and have the internals beefed up, change the heads, cam, intake, EFI, exhaust, gearing, and a 4L80 transmission. Probably putting a modern LS engine would be better; however making the 403 come to life and look stock is the direction I am wanting. I would like to see north of 300 hp…if possible.
I had a 79 Buick Riviera with a modified Olds 403. It’s a long story how we got to that point, but damn was that a fun car. Great sleeper. I actually blew past a cop doing 100 mph over the speed limit once. I did all sorts of other stupid things in that car too.
I purchased a 1979 Trans Am 6.6 L 403cid V8 with 45,000 actual miles on it. It was manufactured in CA, so therefore it has a catalytic convertor. I need to change the oil and filter and the previous owner did not document what he had used. Do any of you fellow trans am owners have suggestions on filter brand and oil brand and the weight of such oil. I believe that I will use a 10w30 or 10w40 weight. I never run the car in the winter and it is stored in a heated garage over winter. I can’t seem to find out any information on this subject. Very frustrating.
Hi, there. Welcome here! This isn’t really the right board for these kinds of questions. Undoubtedly there is at least one enthusiast board for cars like yours, and that would probably be the better place for tips, hints, and technical advice. Have a thick skin, though; oil and filter brand and weight discussions (and spark plug brands, etc) can inspire religious levels of fervour and acrimony.
That said, even the worst of today’s engine oil is vastly better than what was available when your car was new. Pick a major brand of the lightest viscosity grade recommended in the owner’s manual for your driving and weather conditions—a higher viscosity grade is not better or more protective. Likewise, get a reliable major-brand filter.
Note that the catalytic converter isn’t on your car because it was built in California. Pretty much every US-market ’75-up GM car had a catalytic converter, no matter where it was built, and most plants built cars to a variety of different specifications for different destination markets—the catalytic converter was a delete-option for Canadian buyers through ’79 or ’80, for example, and cars built for export to unregulated countries had scarcely any emission controls at all.
Speaking of the catalytic converter, take a look at this article to learn why you might want to replace the pellet-type GM original with a monolithic converter.
Just about any oil will be fine. QS Defy has lots of ZDDP for non-roller cams, so that might be a good idea.
Wheeler, there is an oiling Achilles’ heel with this engine.
The aluminum rocker stands, particularly near exhaust crossover, tend to wear.
Of course shavings then go into circulation.
Maybe 40 years on there’s been a specific remedy developed for the ailment?
I messed with ’60s Oldsmobiles, had some strong runners.
By ’77 the curtains were almost drawn, so it was neat to see the “last gasp” 403 being introduced. lol
I had high hopes and started hunting for one right away. It didn’t take long after introduction for the first wrecked rent-A-car to give up its heart for study. lol
Love those old chickens but honestly money spent modding your car is not smart. Decreases the value and reliability. In the long run that same money and plus all the motors, transmissions and other parts you blow can be spent on another hobby. Take like cycling/mountain biking, kayaking, archery, guns, working out/exercise whatever. Minute for minute you spend most of your time actually enjoying your activity with little maintenance vs always worrying about how it sounds, every noise, every new smell of gasoline, exhaust or coolant you take a whiff of, every loss of fluid, dropping level you find. It gets old fast. I went through the modding bug a few years ago and while the initial satisfactions of driving such a special vehicle seemed awesome the issues I had vaccinated me pretty strongly against the process going forward. You have get it out of your system when people tell you it’s a silly idea you don’t want to listen but I wish I had taken that money/time and invested it in something that gave me back a better “fair share” of what I put in instead of creating tons of car headaches and having nothing to show for it.
I had a 79 Buick Riviera with a modified Olds 403. Great sleeper. I actually blew past a cop doing 100 mph over the speed limit once. I did all sorts of other stupid things in that car too.