Do you mean 'Five Million Years To Earth' aka Quatermass And The Pit?
Yeah that's it!
It has been a while since I watched that one.
Almost impossible to find that one on DVD. I saw it as a kid in the theater and it scared me too.
Another movie that really scared me as a kid was in the late 80s with the movie "The War of the Gargantuas" when the green Gargantua comes out of the ocean and attacks the airport and eats the woman and spits her dress out.