Timing chain ???'s

[sm87xj]

Hello,

I need some help and advise on my timing chain/set replacement, a little history, I picked up my 1987 4.0 XJ pretty cheap after the previous owner had it parked for over three years because of a huge oil leak, and other minor issues. I got it running and found the leak was the harmonic balancer wore a grove/canyon in the timing chain cover. The engine has a fuzz over 300k on it, compression on all cyls is in specs it actually runs great minus the oil leak.

Now the question, I have the font of the engine all torn down to the timing gears, was questioning changing the timing set but have decided to do it, based on multiple google searches and that it has 300K on it. problem is I have no timing chain cover on it to set the engine to "0" or TDC. I have never done a timng set before and dont want to screw things up. Is setting it to TDC really necessary, Is it as easy as alinging the sprocket timing marks as the books say? is there a better way to get the engine timing set to "0" before I pull off the gears and chain, or what is the best way to change the timing set in the torn down condition the engine is in with out messing up the timing settings??? open for any and all suggestions, thank you in advance.

[4.3LXJ]

Aligning the timing marks is as easy as they say. Only one thing you have to do is make sure you are not 180° before you disassemble. To do this pull one spark plug and rotate the engine by hand until you get a whoosh out the hole when your thumb is over it. Then align the external timing mark and this will be TDC