I am in the process of adding another Trans Am to my collection. This one is a black and gold, Y99, t-top 83 with the 305 4 barrel, 700R4. The engine is OK, but it is gettng tired. How will a GM replacement 290HP 350 work in this car. Any problems getting it to fit? I want to keep the OEM breather, an OEM LOOKING carb, and basically a stock looking engine bay. The car is very solid, and pretty clean. I want to keep it looking stock, but since I will be replacing the engine anyway, figured that a 350 crate engine might be the best solution for my needs. My plans are to restore the car back to look OEM, so it will have stock exhaust, wheels, paint, ect. It will be a weekend cruiser. Thanks in advance,Charles

 

The only issue I see, is that you probably will need to upgrade the carburetor to 350 specs. For an electronic quadrajet, that would be metering rods and jets.

The guys on the carb forum can help you get it 100%. The rest of your stuff should go straight from the 305 to the 350 with no issues. There may be an issue with the factory ESC module or knock sensor too, but not sure. I would try it first with the 305 stuff.

I know you'll have to change the carb stuff because a bigger engine needs more fuel.

 

Thanks. That sounds pretty simple. The exhaust manifolds, pipes, and cat from the 305 will not be too restrictive for the 350?

 

I did that exact same thing to my 84 T/A, dropped in a GM 350 that I got from Summit. There were no issues at all and I didn't have to change my carb in any way. It's been 5 years and the engine runs perfectly with the stock carb.

Joe

 

I am not surprised, because the ECM controlled carburetor is very good at adjusting to different varied conditions.

The manifolds on the Trans AM flow plenty, and the rest of the exhaust is more than adequate for a 290HP engine in an otherwise stock car. Now, if you were talking 305 TBI manifolds, then no way. The carb and TPI pieces seem to be fine.

 

Did you see much of a power gain from the 305 to 350? I would think that the 350 would run lean with the carb jetted to 305 specs?

 

The ECM should adjust the carb to run the 350....there is not much of a jetting need difference for a stock engine, and the Quadra-Jet is a very adaptable carb.

...but I'll bet the 350 runs waay better than the 305.