Some rattle at idle and mid range is normal with the LA engine. A little crankshaft slop is usually normal as well. Of course since I can't hear your engine, I can't promise you that your rattle is normal, but I can tell you that the LA's I have owned do rattle at lower rpms. Good little engines though. Not big on power, but usually pretty reliable and will take a pretty good lickin and keep on tickin. The O.S LA engines remind of the old ford 300 6 cylinder engine. The lifters will hammer and rattle, the engine might smoke and be plum wore out, but it will just keep going and going!