|Quote, originally posted by Mk2Fever »|
|Chains also probably cause a lot more damage if they wear out and blow up in the engine bay as opposed to belts |
Also- cars that have chains typically have nylon guide rails that also act as tensioners. Factor in the issue that timing chains need to be run in oil, so add an oiling system for them.
Some cars, (circa 2000 audi 4.2 V8, v6, and 1.8t) engines have a chain and a belt. Each cyl head has a single pulley for the belt and a chain between the two camshafts in each head. Chains are often touted to be a "lifetime" wear item, I have seen them fail much before the end of a vehicle's "lifetime." At any rate, the chains in these audi motors, are tensioned by a pair of hydraulic rams with nylon rails on both sides of the chain to advance or retard the intake cam timing.
These nylon rails are the weak point. If you get an owner who uses cheap motor oil, which most people do, the rails wear out quickly, and become brittle. Eventually they break off and take the whole set of intake valves with them when the chain skips a few teeth. The other issue is that these tensioner rails are not replaceable by themselves (the dealer doesnt have a part number for them) so to replace the rails, you have to buy the whole tensioner/adjuster unit to the tune of $6-700 each.
I'll take the belt thank you.
VW VR6 timing chains are buried beneath the rear cover of the engine, which means that the engine or transmission has to come out to get to them. The chains are again said to be a lifetime part, but I, again, (comma use faux-pas) have seen tensioner rails worn completely out at 120Kmiles when the internals of the engine were as fresh as the day it rolled off the line.
Belts on the other hand, are cheap, the rollers actually have bearings in them (as opposed to nylon friction rails), and in the grand scheme of things are pretty easy to change.
Also- if a person pays attention to their scheduled service intervals and planned for a timing belt change (financially) it shouldn't be a big deal. Wheras a person who owns a car with a chain, and "lifetime" service interval comes into the dealer at 120k with bad noises and bent valves because the chain skipped a tooth, because their tensioner rails wore out, the dealer is just gonna shrug at them and try to sell them a new car.