How much slack in GM 4.3L timing chain?

I started working on my 1989 GMC Safari to repair a coolant leak from
the water pump interface to the block. Saw that the original
crankshaft oil seal was leaking a good bit so I removed the timing
cover. On the tension side the chain is pretty tight, but on the
nontension side, I can wiggle about 3/8" of slack. The teeth of the
sprockets look pretty good but the van has 165K miles. Is there a
tolerance on chain slack? My Haynes/Chilton doesn't call one out.

Thanks!

Barry