1:40 should be doable, but don't dawdle. I have made the T4-T1 pmCO to LH transfer myself before. As others have mentioned, your biggest risk is clearing transfer security at T1; the lines there can be quick or slow. There's no rhyme or reason, and no way to predict it.
You *should* be good, but you may want to come pre-armed with a fall back plan just in case.