what year are they,the carburated ones,the fule pump diaphran can leak innternally,and let gas into the oil,i have seen this,if you dont catch it right away it can do a lot of damage.Gas dosne lubricate very well,and wipes out every bearing in the motor if you get a few quarts of gas in it,which isnt hard to do,if your guage watcher,and have guages,you'll nitice low oil pressure,and you should smeel fuel when its hot,and the engine will be noisier than usual.If its flooding the top end,and spark plugs,usualy the carb is leaking down,or the flaot is stuck.This usually wont dilute the oil very much,but it wint start,until you replace the plugs or burn them dry.
This a bit off-topic, but it's a tale of woe about flooded engines, shade tree mechanics and Kodak moments.
Whole bunch of years ago a neighbor had a Pontiac Lemans that sunk a float. It was maybe 10 years old, but absolutely cherry and flooded badly! It was a nice quiet Sunday morning and we heard him cranking on it, no start. Cranking really fast,, like maybe the cylinder walls were washed down and he was loosing compression as well.
Pretty soon a crowd gathered to watch/asist/join the fun. One of them was a sometmes/sorta mechanic so people deferred to his "expertise". This is all going on about 100 feet from my kitchen window. Every now and then I'd look out to see what they were trying next.
They pulled the plugs and burned them dry with a propane torch. It coughed once and then nothing. (keep in mind that NOBODY thought to disconnect the fuel line to keep even more gas out of the works).
Finally Ol' Ace decided that they could flash the torch into the plug holes and burn the raw gas out of the cylinders. Good plan,, do it!
There comes this very low pitched, and VERY loud WHOOMP! I looked out the window and there's this circle of owner/mechanic/onlookers/coaches around the car. Looked like tourists at a luau. Smoke is rising from under the hood and under the car. No flames, they all stayed internal.
Strange how that happened, all them gas vapors must have flashed back into the engine. The resulting low grade explosion had force enough to jug the valve covers up around the bolts and the oil pain down around it's bolts too. Ol' Ace declared, "Well,, that one's spent" and the crowd dispersed. The nice cherry Lemans went to the crusher the next day.
The one with the Holley,Holleys flood out constantly,either its got a stuck float,(very common),to high a float setting,or a backfire ruined the powervalve,and its now leaking down thru it.I liked the Holleys for power,but they sure do flood out a lot.