Basing myself on synchronic and diachronic data analysis, I argue in this article that size nouns (SNs) such as bunch/load(s)/heap(s) of within binominal NPs display synchronic variation which can be hypothesized to be the result of grammaticalization processes. Synchronically, I propose that SNs have two major non-head uses, a quantifier use, e.g. a bunch of people walked in, and a valuing(-quantifying) use, in which the referent is evaluated rather than quantified. The latter is restricted mainly to bunch/load of, e.g. What a bunch of gobbledygook. The semantic and syntactic reanalysis of SNs as quantifiers has recently been acknowledged (e.g. Traugott forthcoming), but the valuing use of SNs remains largely unrecognized (see Brems 2007). On a theoretical level, it will be argued that head, quantifier and valuing(-quantifier) SN-uses synchronically have to be studied as collocationally constrained constructions in that the semantico-syntactic parsing of each SN-use links up with specific collocational patterns (Sinclair 1991). Head uses are restricted to sets of (un)count concrete nouns, whereas quantifier uses team up with all sorts of (un)count concrete as well as abstract nouns. Valuing uses show restrictions to concrete animate and abstract nouns, which they typically evaluate negatively, and have negative semantic prosody patterns, in which the SNs themselves come to predict negative collocates (see Louw 1993; Stubbs 1995; Bublitz 1996). The grammaticalization of SNs will be hypothesized to involve not only processes of semantic generalization and collocational extension, but also collocational reclusterings characterized by particular semantic prosody constraints. The latter are not traditionally associated with processes of grammaticalization and hence offer new insights into the semantic changes that may accompany grammaticalization.