I have a77trans am, basic 6.6 400. The olds 403 came as a stock option too. I read an article that you could really beef up the 403...350 hp for around 1500 bucks. But what could i do with the 400 for $1500? I wanna keep it somewhat original, but with some muscle. which motor should i stick with? I hear the 400 is kind of easy to tear up when built. But then the 403 only has around 185hp/325lbs torque with 7:1 comp from factory....kinda weak. someone help me with my decision please.
you can bump up the compression on the 403 by putting 68-70 olds 350 heads on it. i had an '80 formula w/ a 403, 69 350 heads, and an edelbrock performer cam that would simply incinerate the tires w/ an open rear (and i mean both tires, no brake torquing) that was w/ a stock aluminum 307 intake and stock exhaust, so if you do more, it oughtta fly. the 400 poncho is stronger to begin w/, though...
you could do what he said. or if you wanna go another route stuffing a chevy drivetrain in it is popular for many reasons, cheaper easier to find parts, easier to work on. not to mention swapping that out with a chevy will shave a good 50 pounds. (wide angled pontiac engines weigh alot more) or you can stick with the motor you have now and with a cam some cheap junker heads to boost compression and a few other mild changes to your motor will give it decent power. get like 9-10:1 compression in it, a mild cam, and hei with a good 4 barrel and intake should put you well in the mid 300s for both torque and hp which is all you really need for a street machine.