Carb/Ignition Issues????

[ZZ3ElCamino]

Hey guys, I have been having some issues with my car lately. Out of the blue, the car began to run really rough when I was up to speed and began dumping gas in the cylinders. Therefore I had some blow by in the cylinders and now have gas in the oil. I purchased a new/used carb when I built the car, so I was thinking it may be the carburator that was bad. I recently purchased a Holley Street avenger and and installed it and it seems to be having the same problem. The car will idle the way it is supposed to once the car kicks off of fast idle, but when you try to give it any throttle the car will fall on its face. So this brings me to my question. Might this problem be ignition? I have an older Mallory HEI dist. and I have not had a chance to check the timing. I was hoping someone could provide me with some suggestions. Thanks a bunch.