The Oldsmobile engines typically had a fairly high initial timing....coming in at 18-20 degrees before TDC. That's assuming you're talking about a fairly stock 403.
a 300 302 350 403 455 but 455 were rarely used in the the 79taNot even remotely correct. The '79 T/A had 3 engines available. The first being the Pontiac 400....and all of these will be mated to a 4 speed transmission. The Olds 403 is next and for California T/As only they used a Chevy 305.
Pontiac did not make a 403 but offered a Oldsmobile 403 in the trans am, lots of work and modification to put in a 1988
Have the timing checked , sounds like it might be off.
I didn't see a specific year year you're interested in, however a 1978 Olds 403 is listed as 18 degrees initial timing (detach and plug vacuum advance hose while setting initial advance).
The time chain is located under the timing chain cover, which is behind the fan and under the water pump.
Place timing marks dot to dot using a straight edge from crank center to cam centerline
Near top of water pump
Around 180HP from the factory.
Because the correct sum of 305 and 98 is 403.
from factory they offered a Pontiac 400 w/ 4-speed or the Olds 403. 301 was also available.
probably the power brakes if you have them and the vaccum modulator on the tranny.
403.