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Author Topic: 403 modification  (Read 3992 times)

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403 modification
« on: November 23, 2006, 11:29:49 AM »
Are there any modifications that I can do or have done to my bone stock 79 trans am 403 olds engine. I would like to keep it as close to stock as possible but would love to add a few extra hp.


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Re: 403 modification
« Reply #1 on: November 23, 2006, 09:55:25 PM »
There are alot of modification to do to your car to get more power.  You can change alot of things and still "look" somewhat stock.  You can change the heads to 350 heads to increase the compression.  You can change the intake to an edlebrock or something similar.  Then you can grind off the edlebrock name and paint it to match the engine.  You can also change the carb as well.  When the hood is open and the stock air cleaner is on, you can't see the carb anyway.  You can also change the exhaust system to something from Ram Air Restorations.  They sell a complete kit that also incluse stock looking manifolds that have been modified to allow better air flow.  The afermarket marketplace is so large and there are so many choices out there as far as upgrades.  I would talk to a local engine guy to see exactly what you want to go for and what horsepower you want to end up at.
Brett Campbell
1978 Trans Am, 1989 Trans Am, 1998 Trans Am


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Re: 403 modification
« Reply #2 on: June 21, 2007, 12:19:45 PM »
Find a nice set of olds 350 heads either #7's or #6's those usually came on olds cutlass 70-72. That will help bump the compression up. Have a machine shop put in larger valves as well. The stock Valve size on the 350 heads are small for the 403. Next find a decent cam. I went with comp cams XE274. Kinda rough idle not too bad still able to use my power brakes. Edlebrock performer intake, I left it as is. I also went thru the stock Q-jet. Nothing like those huge Secondaries :). Dynomax headers with Pypes exhaust. and -8An fuel line from the sump to regulator.

The only thing i wish i woulda done was put a windage tray in it. As my budget was kinda slim when building it up. Another thing that will give your car a little motivation. Rear gears. Something in the mid 3's. I got a 3.42 with an Eaton posi. Have yet to take to the track to see what it does. Lack of time :(

But if you got any other ?'s PM me

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Re: 403 modification
« Reply #2 on: June 21, 2007, 12:19:45 PM »


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