With all of the discussion about timing sets lately. This tip from the rockauto.com newsletter is timely (excuse the pun).

"The engine crankshaft turns a timing chain or timing belt to spin the camshaft. Engines with worn out timing belts usually run fine until the belt breaks and the engine stops. High mileage timing chains often stretch long before they break and the engine will continue to run. A stretched timing chain might cause backfiring, loss of power, exhaust smoke, rough idle / acceleration, and other problems resulting from incorrect valve and ignition timing. These symptoms can be hard to diagnose individually. Is the PCV valve loose? Is the catalytic converter clogged? Is a spark plug wire bad? Is the choke stuck? Did a sensor fail? To diagnose a stretched timing chain, consider the vehicle's repair history (the spark plug wires were replaced last month). Watch for ignition, exhaust, and fuel symptoms occurring all at once. Listen for noise from the timing chain cover as the loose chain rattles around on the chain sprocket, and consider the vehicle's mileage.

Replace the timing chain, sprockets, and other timing components as a set to avoid prematurely stretching a new chain with an old gear."

 

VanGo, this is indeed a great tip. Plus it makes perfect sense on high mileage Aerostars, when trying to fix sluggish engine performance. Also, with my experience with 4-cylinder timing belts, it's rarely the belt actually breaking. What happens is the "teeth" or "ribs" on the belt gets brittle and breaks off. The belt turns, but with no teeth to bite and turn the cam sprocket, nothing works, and the engine will never start. I've never had a timing belt break when driving. It always happened, when trying to start an engine, engine fires, then stalls 1-5 seconds later. Engine turns over with little or no resistence, in which I knew the timing belt was shot. The early Omni-Horizon engines, with the 1.7L engines, you could take the oil cap off and shine a flashlight inside to see the top of a cam lobe. If you had a helper crank the engine, with the flashlight the camshaft did not move, you could diagnoise timing belt issue in 1 second. Ed
PS One reason for premature wear on cams and timing / valve train wear: Using too thick of an oil, than recomended. Cold, thick oil not pumping quickly on cold starts, resulting in numerous 'dry starts' and metal on metal contact. This is not just my opinion, but well documented all over the internet. Anyway, thanks again VanGo for this reminder on timing chains.

 

with the metal chain/gears timing chain setup of the Aero V6's, the usual failure mode is the chain wears and stretches and with the gear teeth wear, allows the chain to jump a tooth or two

prior to tooth jump, engine will experience rough running, missing and backfiring from wrong crank/cam timing caused by slack in chain
i've seen Chev small blocks still running but poorly and the chain can be touched together between the gears
changing oil on schedule adds to chain/gear life, replaces antiwear and antifriction additives...the latest SM class of engine oils probably do not have enough antiwear and antifriction additives for our old loose tolerance cam chain/gear engines...SM is a gimick for cat. life extension and polution reduction
use SL oil or add antiwear antifriction additive such as in STP engine treatment or Valvoline engine treatment to SM oil or risk your Aero engine

 

96_4wdr:
Would the same advice apply to other OHV engines as well as to Aerostars?
Ray Mac

 

i use 16 oz of Valvoline engine treatment with extra moly, zddp and calcium additives along all with 1 qt of Redline 5w30 for extra moly and ester cleaning, fill with Mobil 1 5w20.
4L is quieter and smoother running.