I just finished rebuilding a 289 for a '67 coupe and the darned thing won't catch when I start it. We have gone back over the wires (getting spark), the firing order order(tried it a 180, just in case), check TDC 10 times (checking valves as well) tried two different carburetors ( the original and a Holley), Advanced and retarded it as far as we can, and the darned thing won't catch. I'm open to any suggestions or ideas of what the probem might be.