My 283 did not have a heat riser from the factory, check the shop manual - some models have it, some don't. Mine drives the same way, just takes time for the intake and carb to warm up. If the engine loads up with the choke in use then you need to adjust the fast idle to compensate for added fuel when cold.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy