Timing chain replacement

[SinceByMan]

I have a 91 dohc 240 and Im going to replace the water pump, I dont know if I should replace the timing chain, it seems like a good idea but Im terrified about messing something up. Ive read the posts about timing chain replacement but Im still a confused, what precautions should I take and are there any helpful hints anyone can give who has already done the replacement? any help would be greatly appreciated.

[Meantime]

Replacing the timing chain is not an easy or fast thing to do. It involves quite a bit of work. As a result, I don't recommend doing it unless it's necessary.

Which leads to the next question, when is it necessary? Well, the timing chains don't exactly have a replacement interval. If yours is not making any noise, which is typically a rumble or ticking from the front of the engine upon startup and idle, and the engine runs fine, then don't worry about it. It will cost you anywhere from $200 to $400 for the kit, and then give yourself a good 3 day interval to do the job.

If you are really curious, pop the valve cover and the front sprocket cover off and see what the chain/guides/tensioners look like. You won't be able to see the whole assembly, but you will see the upper chain, sprockets, upper guides and upper tensioner (if I remember correctly). Excessive wear or slack in the chains, or score marks on the covers, will be a clue the chains probably need to be replaced. That's the one nice thing about chains...they will usually give SOME warning when they need attention. A belt will just go quietly into that bad engine-destroying night. Hope this helps...