My GMC 6 was a 228. It was very well used, but when first started at idle it was in the range of 20 and at 30 or 40 miles per hour it would stay close to 30 or so (by the dash gauge) in cold or hot weather. In the summer at a red light the pressure would drop down significantly at idle. Enough of a drop to make you nervous if you worried about things like that. I think I just ran 30 weight oil in it. Wasn't a bad engine at all, but it didn't have the pep the 235 had. I had to replace a head gasket and while the head was off I had the guides knurled and I lapped the valves. It ran much smoother after that.
Jon
