Acouple engine questions?

Well i just bought a 02 firehawk. Bodys in amazing condition. However theres been a used engine just put in it. It has 70k on it. I've driven it and first problem is at random times i get this really bad clicking sound coming from my driver side valve cover. It only happens at random times. Its only happened to me maybe 3-4 times within a 2 week span. The other problem i have is, im getting this clunking popping sound while driving. It sounds like its coming from up front but i cant tell. reving up the engine doesnt make the noise worse or better. So im guessing its drivetrain? It just sounds like a clunk clunk clunk. I know im not really discriptive, i've taken it to afew mechanics *engines under warrenty* and ofcourse it didnt make the noise for them. As soon as i get home it starts up again. I thought it was a bad lifter, but wouldn't that cause it click all the time??

thanks for the help guys

I would say the best thing to do is go to a specialist. I have all my work done at local shops that know LS motors and F-Bodys inside and out. I find they know alot more and usually cheaper since they usually know the tricks to get it done and charge by real time not book hour like shops. I had my pulleys installed for $40 at a Performance shop when a regular garage was going to charge me over $200. They may have better ideas or just have them take the vavle cover off and check it.
I had clunking noises in my other car. If it's an auto it could be the tranny mine clunked untill I had it rebuild. I believe u joints on the driveshaft also make a clunk noise.

Yea i need to find a good specialist. . because the 2 mechanics i took it to obviously didnt know much about it. :(.

The clunking sounds is ball joints or tie rod ends IMO, if its up front. It could be the clutches also sticking in the differential in the rear end , if it there.
The clicking could be piston slap, but it also might be a lifter, pushrod or rocker arm since its in the valve cover. What type of oil do you use?

Gotta get greasy guys! lol

I'm a painter and a body man. I do my brakes and some suspension. Some bolt on's(Tb,Volant, 160 stat, hid kit's). Inner motor workings I leave to pro's. I don't mind getting greasy. I just like the work to be perfect. Makes the job faster, easier, and better. I stopped working on my motors when I got ride of my 93 5.0. Too cramped in these F-bodys. I'll stick to painting and have the shop down the street get greasy. My car likes it better that way too.