Do you have to drop the oil pan to change the timing chain and gears ? I know of a couple people who did not and now they have a small oil leak where the timing cover meets the oil pan. If you do is it a PITA , it may help that my exhaust will be off since I will be putting headers on at the same time . BTW my chain is not broke but I thougt it would be a good idea to put a new one on since the car has about 100,000 miles on it and is going to be down for about a month while I am doing the headers and porting and polishing the plenum . Also chain and gears are inexpensive.

 

After 100k miles on the engine it definitely is time for a new timing chain. Dropping the pan would help but its unnessecary. When I did my timing chain I just put wedges between the pan and block, to separate the two enough to put the timing cover chain back on the front of the engine. Then, I used silicone inbetween the pan and the block when I bolted the pan back up. Hasn't leaked a drop .

 

The oil pan doesn't need to be completely removed, but it should be loosened so that the front edge can drop down at least ¼" (7-10mm). If you remove the first 6-8 bolts from the front on each side, and loosen the remainder, usually the pan can be dropped that much easily.

However, just because the chain and sprockets (not gears) have over 100K miles on them, they may not be worn excessively. GM stopped using plastic teeth on the cam sprocket many years ago, so your '90 should be all iron. If the engine has been properly lubricated, the chain could be fine. I've removed chains on 100K engines that were no more loose than the new replacements. Check the lash in the distributor before you get really excited about changing the timing set.

A month to install headers and port the plenum? You must be meticulous. And there is no need to polish the plenum, since there is no benefit. Unless, of course, you are polishing the outside of the plenum for aesthetic purposes. Forget about any polish in the inside, since you could potentially lose some performance.

 

My '83 LG4 had the (plastic? I thought it was nylon...) sprocket on the cam. It was replaced at about 85,000 miles and had some play in it (more than the replacement did.)

 

Thanx for the info guys,I definetly dont want to mess with the timing chain if I dont have to ! And yes I am very meticulous ,I will only be able to work on it on the weekends,that is why I am figuring about a month.I plan on cleaning up the whole engine compartment and painting everything,as far as polishing the plenum,that will only be the outside and the runners for looks.My intake manifold gasket is leaking so it all has to come off any way.BTW, what are the better wires,cap & rotor?, Accell or MSD??