Hitman's Pontiac Trans Am Forum
Trans Am Information => Trans Am Tech => DriveTrain => Topic started by: GhostRider on December 03, 2008, 01:34:42 PM
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Hello!
I have 1979 WS6 that I bought new. 403 w\auto and I have approximately 95, 000 miles on it. Totally numbers matching. It runs and shifts fine, but I thought it was about time freshen these components.
I'm thinking about having both rebulit. Any recomendations would be appreciated. What should I do while the motor and tranny are out, etc.. Motor components? I'm thinking about hopping the motor up as much as possible where it can still run on pump gas.
Thanks!
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if it is numbers matching i would save that motor and get a diffrent 403 and build it then you can save the number matching motor for later
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The 403 engine produces a lot of torque, but don't mistake it for a high-HP engine. The block has what is known as "windowed mains" where the area around the main bearing journals is lightened to save weight. This is, unfortunately, the curse of death if you twist the engine higher than about 4,500 RPM. The block flexes and the crank breaks, and that's it. It's possible to install a reinforcing "girdle" down there, but that's not cheap.
The stock 403 heads are large chamber, and the pistons used are "dished" or scooped out to further increase the end volume and reduce the compression ratio. That was done for emission control purposes. You can raise the compression ratio by finding a set of earlier Olds 350 heads with smaller combustion chambers and swapping them out. If you run the math you can also possibly use flat-top pistons (no dish) so the CR goes a bit higher, but don't overdo it because with today's pump gas you don't really want a static compression ratio higher than 9:1.
If you search this forum you'll find that's pretty much the consensus of the 403 owners. It's also the advice given in the February 2009 issue of HPP magazine in response to similar questions from a 403 powered TA owner. The 403 is a good engine, but if you're concerned at all about future value of the car and you intend to twist its tail a bit, I'd take pat's advice above and set the original engine off to the side and get a non-numbers matching 403 block to play with. That's just my take.
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I would put a Buick 455 in it. OOps, sorry I already did that very silly thing.
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Despite the collector value of any second gen T/A I've never been a fan of 403-powered models. I've owned a '78 S/E T/A and a '74 455 T/A, both Pontiac powered, and have never had any problems demonstrating to Olds- powered 'Bird owners why the Pontiac engine is better. I always find it funny too, when the Olds T/A guys think their engine is better when Pontiac only installed them due to a shortage of Pontiac 400s and to use a surplus of 403s sitting in some GM warehouse.
Geno
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Dang ... 50 posts and Geno is off the chain! ....he's absolutely right of course about the olds stuff.
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Sorry, dude, not trying to step on any ones toes but I've had my 'Bird for 20 years now- back then the Olds guys knew their place and when one didn't the Poncho guys showed 'em why we're the 'big dawgs', at least as far as Firebirds go. Now there are plenty of newbies trying to tell me they know more about Firebirds than me- heh. ::) Not that I'm an expert, but I used to be the smartass kid who knew it all because I drove a T/A- now I'm the 'old guy' who just laughs anytime the youngsters tell me all about second gen Firebirds and Pontiac motors. ;D
Geno
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No, it's cool. I only run Pontiac motors in the Trans Am per the signature ..
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Yeah if you dont wanna spend big bucks it is much easier to find a pontiac 400 motor vs the 455. But i agree with them. I never liked the 403 motors. The fact that they didn't even make them in a manual trans tells me that they were not meant to beef up. But i would def keep the 403 if you are thinking about keeping it until it is worth some big bucks.