Parameters in the title are very approximate but I will share my discovery and see how much more power you get out of your 455:
I found my secondary throttle leaflets were not opening completely. When I went about trouble shooting this,among other issues, I found that the
rubber grommet that connects the accelerator cable to the throttle carb linkage was worn through completely. This loss of an 1/8" space prevents the
secondary leaflets from opening completely. I was able to get a replacement from Aplied GMC and now I have full opening of my secondaries and more
power. Pretty cheap project with big hp gain.
I found my secondary throttle leaflets were not opening completely. When I went about trouble shooting this,among other issues, I found that the
rubber grommet that connects the accelerator cable to the throttle carb linkage was worn through completely. This loss of an 1/8" space prevents the
secondary leaflets from opening completely. I was able to get a replacement from Aplied GMC and now I have full opening of my secondaries and more
power. Pretty cheap project with big hp gain.