350 solid lifter lash?

I have an 84 c-20 truck with a way overbuilt 350 engine in it. I didn't do it, I am just trying to make it run better for a while till I finnish building another 350 the right way for a truck. It has a solid lifter cam in it and I have no idea who made it or how big it is but it has a terrible idle. Worse than my old drag car. Huge cam. Right now I got it running pretty good for what it is but when it heats up it gets pretty sluggish. I strongly suspect the valve lash since it is only 6-8 thou hot. The only solid lifter engines I have ever worked on , aside from deisels are usualy a lot more like 12 to 22 or so. I was thinking about taking this one out to .020 hot. Anyone see a problem with that much for a solid cam street engine? Or have a better suggestion?
Previous owner spent all this money on it and left stock manifolds, worn out qjet and a very worn out hei on it. I already replaced all of that. No wonder he traded it off so cheap. Moron! Plus it is a 3/4 ton chevy truck. Sometimes I would love to see into a persons brain like that and see what is going on. Probably not much.

Boy that was a quick response. Thanks. You don't think that would get too noisy? I doubt it would. Good point you have though about less lift. I will do that tonight. My 4x4 has some major valve seal problems that I am putting off till next weekend and I have to fix the chevy tonight so I can go hunting tomorrow. You know how embarrasing it is getting passed by little rice burners on an onramp with a motor like that? I pass them once it winds up no problem but it's still embarrasing. I got this chevy to pull my horse trailer but that ain't gonna happen till I finish my motor. It's a 350 4 bolt from an 82 .030 over and I am doing the three angle job with manly valves and have decided on a comp cams extreme 4x4 cam 264 I think was the duration. My pistons are probably gonna be flat tops but not sure yet. My frinds is trying to talk me into 305 heads for a tad more compression but is that really true? more compression? I have a set of them in the garage read to go. I already plan on having to use mid grade gas. I can't afford another super unleaded motor around here. Any Ideas for valve train for a hipo truck engine? roller vs stock and spring type.

Sounds like too much cam for the street anyway, but what heads are on it??What intake did you choose??Carb?? Manual or auto?? I f it is too much cam, you may be better off spending the $120 and getting a hydraulic anyway. Get the springs from the cam supplier.

BTW, our "A fuel" car ran a 396 with solid lift. .026" intake, .030" exhaust 9000+ rpm.