[Mike Klingerman]

With alot of people rebuilding Trans Ams like myself. The 403 seems to be a common Question for alot of people. If somebody did thier research and was able to put togeather a performance package and sell it as a kit. They would be rich. It could'nt be a bum package. It would have to be something that would really wake this sleeping beast up. I've been reading alot of the replies to the big 403 questions and some of it sounds good but nothing really impressive you know what I mean? Replies welcomed becuase if there is a secret out there I'd love to know what it is.
Mike

[Blownolds]

403's have a weaker bottom end with windowed mains. But they can be used up through high 11's without fear. Go to realoldspower.com

[steppenwolf]

or check out http://www.442.com/oldsfaq/ofe403.htm
-z-

[RocketPowered]

Sorry, man. While the 403 has the sweetest bore/stroke ratio on the planet, it was born in the late '70s in EGR land. Change your mounts and a 455 will bolt right in. You can even use the same cam...and distributor...and exhaust manifolds...and water pump...etc...
Good Luck

-Rocket Powered

[Bradless]

I also have a Trans Am with a 403. I found that aftermarket pistons at the time of the build-six years ago, could not be found. I did put in a performer rpm cam. Had to change out the rockers, pushtubes, and istall guides for the pushtubes. I also had the block decked to try and get the comp. around 9.5 to 1. I also installed hooker headers and bullhogged out the exhaust in the heads. I never run it over 5000 rpm out of fear since the webbing is windowed. I found my engine to put out around 350 hp. I also had installed a performer intake-RPM will not fit with the shaker. I recommend frame connectors if you du this sort of thing, since my unibody developed a sixteen inch crack between the seats that I would have never found until seriously bad things happened, had I not changed out my carpet. I figure I only spent 2500 on the engine and headers, so not a bad price for a strong engine. My buddy said he recently rebuilt his 403 and said he bought aftermarket 9.5 to 1 pistons, so who knows, there still might be a way to get a bit more power without butchering like I did. Good luck.