id replace them all... why not your already there. at the bottom of the lifter theres a wheel it has to go in so it will roll on the cam (very easy to get right) as for the ls7 lifters idk if they will work but just get some stock lt1 lifters youll gain nothing by "upgrading" them. yes theres a valve cover gasket but its reusable

Melling/Valve Lifter (JB-2079) | 1994 Chevrolet Camaro 8 Cylinders P 5.7L SFI OHV | AutoZone.com

 

i thought that the lsx lifters were the stock replacements now

 

lt1 does not throw much oil with the covers off so you are fine to start and check things out. easy to get cover off driver side and gasket is rubber type and most times can be reused. should take only a few minutes to do. you can replace the one if its bad but your gona have to take the intake manifold off so if you can afford it replace em all. i would suggest you have a buddy thats good with motors reset the lifters once installed. setting lifters is easy but its also easy to get wrong so watching it done first would be best. i am also going to suggest you pick up a repair manual. factory service manual is best but can be difficilt to use for the first timer. chiltons or haynes will probly be better for you to start with.

 

With the engine only having 9k miles on it, I really think you're jumping the gun here. How many miles have you put on the car so far since you got it? I would give it till the next oil change to see if the synthetic clears it up, which it may. I've had synthetic oil clear up a noisy lifter on an engine that had 119k miles on it.

 

ive had a little over 4000 on it when i bought it, i did royal purple first, then changed it 2 weeks ago with mobile 1 and lucas...the noise has seemed to always be there...i dont beat on it,, ive never even had it full throttle if that makes any difference. Im pretty clueless when it comes to this subject