Author Topic: 79 ta x code  (Read 146 times)

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Offline hemiboo

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79 ta x code
« on: September 10, 2019, 01:15:57 PM »
bought new 1979 true Daytona pace car , 403 olds auto. my question is many but for now , can a 403 olds be built for power. I was told cant be done, put a chevy 350...soo typical. it was rebuilt with no documents, 20 years ago-before all the web site suppliers, no internet help.

Offline Aus78Formula

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Re: 79 ta x code
« Reply #1 on: September 10, 2019, 08:55:40 PM »
You need to get rid of those 'put a chev in it' people in your life. The 403 already has more torque than a 350 will see, and it's stock and strangled down to suit an emissions role. You can get some very decent power out of one and still appear stock under the hood which can be important with original cars or those that don't allow much in the way of taller intakes or carb swaps. A slightly warm 403 and gear swap will leave most 350 posers behind, and all before the revs could rise.

Secondly, you will have all sorts of dramas getting a 350 swap and not end up bolting the shaker to the hood. It already sounds like you are somewhat proud of the fact you have a genuine model, rather than a Camaro. An engine swap will see the value of the car not even match the engine you just put in.

Rebuilt is probably just that, slight overbore but otherwise stock replacement, certainly not what you will get excited over. But if still in good order you can still double the power with a few clever bolt-ons. Plenty of posts on these already.


Offline Stringer

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Re: 79 ta x code
« Reply #2 on: September 13, 2019, 09:33:42 PM »
Yes the 403 can be built for power if you know what you are doing. The motor "got a bad wrap" for two reasons. 1) The motor has Siamese pistons - meaning no water jacket between them  2) the lower mains are "widow mains" - meaning they have holes within them and can not handle large amounts of torque.

The 403 is a fine motor. It is what I have in mine. It can also be built for power. While I have not done it, I have read you can push upwards of 500hp and about the same torque before the issue with the mains starts to haunt you.

Stock the motor is 185hp and 315ft lbs of torque. Running true dual 2.5 inch exhaust and headers would probably put you close to 200hp Adding fuel injection setup (which I hope to due to mine) may take it up another 15.  Beyond that would require a different cam setup and maybe boring the cylinders - and the hp ranges are many.

If you build it, it is recommended not to bore the cylinders more than 20 thousand over, because of the Siamesed cylinders. There is the potential of developing overheating issue if you go beyond that range (or so I have read).

The car was "fast for the its day...... but is not fast for today" as I like to say. It's sill quick car and is fun to drive. It feels faster than it actually is, because of the torque.  So, unless you are looking to build a power house, I would stick with the 403. A few cheap mods and she really comes to life. If you do change I would go with the Pontiac 400. The 400 is the better motor @ 220hp and 320ft lbs of tourqe. No Siamesed pistons and no widow mains. The damn thing can handle almost anything you throw at it.

« Last Edit: September 14, 2019, 12:13:40 AM by Stringer »

Offline Aus78Formula

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Re: 79 ta x code
« Reply #3 on: September 14, 2019, 12:30:55 AM »
My previous 403 was 60 thou over. Had no idea until pulled it down. No overheating issues ever, cooling and engine well maintained and had plenty of cooling options open to it if needed. It just wasn't suitable for the piston plans I had. Picked up another block for less than cost to sleeve, might be different today. The KB piston option is for 24 or 39 thou over and are totally fine.There's a few older How-to build a 403 articles online. They are a guideline only. Not only are they outdated but full of incorrect assumptions based on little of fact but sound iike good advice. Many of the issues apply to many engines and not because they are a 403.

Offline Stringer

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Re: 79 ta x code
« Reply #4 on: September 14, 2019, 12:22:43 PM »
I always question the boring amount.. When I had my heads off a few years ago it seemed like plenty of steel to work with. It is good to know what it can really handle.