Doesnt seem to be much posting going on here, but I'll try anyways. I bought a mint 1984 Seville bustleback, last spring, with 82,000 original documented miles. when I bought it, I knew NOTHING about the nightmares on the HT4100. I read on here stuff for about a day, then I went & bought the car. Turns out, that the engine in it is a GM Goodwrench replacement engine. It has black steel valve covers, and it says GM Goodwrench HT4100 on them, they are NOT the finned silver aluminum ones, that came on most HT4100. I know there were SEVERAL of these put in with warrenty claims. and there were also many upgrades made to the HT4100 as time went along. Is there anyway of telling just by the engine block numbers WHEN this engine was produced, and what upgrades it might possibly have ? my concern is, if the thing blew up a month after the first owner bought it, the replacement engine might NOT have all the better gaskets, O-rings & better camshaft in it. but , if it blew up in say, 1987, with 35,000 miles on it, then the GM replacement engine likely has the best of everything in it. The junkyards around here are full of 82-90 Caddys with HT4100s that have milky oil or busted cams & bad bottom ends.