I've got over 239,000 miles & was wondering on replacing my timing chain but since its non interference & having no issues I'm gonna hold off. Someone mentioned rpm fluctuation & I've recently ordered IAC sensor(idle air control) to fix that hopefully. That's the only issues I've had with my rpms. As far as the spark knock on acceleration (exspecially between 40-70mph) I've always had it no matter the oil combination or fuel grade used. I actually had worse knock with higher octane or non ethanol. I will say the only noticeable difference I've been able to get better end results is a synthetic oil with the better frame oil filter. The $9-10 oil filter w/ anti drain back valve to keep oil in filter & passageways. Other than an alternator, battery, serpentine belt & tension pulley I've not had to anything major in the 90,000 miles I've owned it besides recently replacing the pilot bearing. I think the previous owner replaced the clutch & pressure plate without replacing the pilot bearing & throw bearing. Sorry to deter from timing chain subject but on the other hand Rockauto.com does sell the chains alone pretty cheap so it wouldn't be a terrible idea?

 

Even if the cost of the timing set (chain+gears) is zero, there is the big labor for replacement.
The context is its on an old engine that could be wearing in many other ways, on a vehicle that could be wearing in many other ways.
I scanned through the posts of this ancient thread and would agree about it being a non-issue on a well maintained engine.
If you are in there for other reasons, then sure.
If you considering preventative measures on a mission critical vehicle, then I would be swapping out the entire lump for a rebuilt.
***
Here, as a proxy for durability, pics of chain stretch on my previous 120K mile Vulcan 3.0 (left), versus my recent scratch build (Search Vulcanstein thread, from mid 2018).
Regretfully not a consistent method or precise measurement, but I think I do see some elongation, resulting in perhaps the cam falling behind by 1 degree (?).
Nothing to lose sleep over considering all the other slop in the overhead valve actuation and spark distributor sensing.

 

imo the hardest part of replacing the timing chain is seperating the clutch fan and water pump.i think the key to long engine life in an aerostar is to make sure the engine never overheats.you will be replacing head gaskets then.

 

I had a 97 Aerostar with the 4.0 in it with 186,000 miles when I bought it and nothing had been done to the engine internals at all. Ran great, ex wife totaled it, it still ran good and was parted out.

 

You can get or rent tools to easily remove the fan clutch. The really difficult part about replacing the timing chain is pulling and later replacing the front cover. To do it right, you really should drop the oil pan first, which means replacing that gasket. It's a little easier to do this on a 2WD van, but on a 4WD van, the front cross member blocks most of the access to the front oil pan bolts, which you need to remove/replace even if you're not dropping the pan.

In addition to not letting the engine overheat, you should change the oil regularly.

 

theres no way to hold the fan pulley on my van to loosen the fan.i had to remove the fan and water pump together and then destroy it get them apart.of course i was replacing the water pump anyway.

 

For my 4 liter v6, there is a tool that looks like a giant flat open ended wrench I used with a 1/2" breaker bar that locks onto the heads of the 4 bolts that hold the water pump pulley to the water pump. Then there is another big open ended wrench to loosen the big nut that holds the fan clutch to the water pump drive shaft. I think this is the set:

https://www.napaonline.com/en/p/BK_7769242

and some local auto parts stores loan them out. I'm not sure if the 3liter v6 uses the same sizes. The tool is also useful for installing the clutch back onto the water pump. The 4 liter engine turns the water pump in reverse, so its nut has a normal right handed thread that you loosen in the CCW direction, and tighten in CW. The 3 liter engine turns the water pump in the normal direction, so it has a left-handed nut thread.

 

Im at 532k miles 97 Aerostar 4.0. Still on original timing chain and gears. Great engine.

 

If you change the oil regularly at 5000 miles, you can keep the engine running well for a long time. Of course, timing gear and chain wear occurs slowly, and you don't usually notice it because the effects get worse slowly. Usually the symptoms are loss of power and efficiency as the cam timing become more retarded. It's a good idea to replace them if you ever need to get into the engine and it has more than a couple 100k miles.

 

I had to replace the timing cover gasket on my '92 3.0, around 180K. Definitely needed to rent a couple tools to get the fan clutch off, and the balancer. Changed the timing set, definitely a good deal of slack on the old ones.