Aron9000

This is something IMO manufacturers should NOT skimp on, the timing gear on their engines should last just as long, if not longer than the piston rings. I know many different makes have had problems using plastic parts in the timing chain/timing gear on their engines over the years. I see this simply as a "bean counter" accounting move. I mean how much more $$$$ can it cost to put actual stamped steel parts instead of plastic junk in your engine's most critical components???

I used to own such a truck with plastic parts in the timing gear. My 1993 Toyota with the "unkillable" 22-RE 4 cylinder had plastic guides for the timing chain. I think both of the gears were metal, but the guides on the chain were plastic. Luckily in that engine, if the guides broke, the engine made a horrible noise and the failure was not catastrophic. That being said you had to strip the whole front of the engine to replace the entire timing set, not a cheap job, especially when you consider I only paid $600 for my truck with that 22-RE engine. Luckily I never had that problem. The Toyota truck people say the earlier 20R 4 cylinder that uses all metal parts on the timing set is a more durable engine, but I do like the 22-RE a bit better since it has fuel injection that is rock solid reliable, along with about 25% more power vs the emissions strangled 20R with a carburetor.

Now I was watching a video of how VW makes their W-12 Bentley engine. I was just absolutely shocked to see they use the same damn stupid plastic timing chain guides as my old 1993 Toyota truck. Now a few years(well many, like probably 10+ years) down the road, these plastic timing guides will get brittle and break. Hopefully it won't lead to catastrophic engine failure in those Bentleys. However, if a timing set change on an old 22-RE pickup is a $600-1000 job, I'd hate to see the bill on a Bentley to tear down the motor to replace the plastic timing guides.

Anyways, I was watching a documentary about the W12 VW/Bentley engine, look at 4:00, 4:10 seconds or so and you can see the plastic timing chain guides I'm talking about. WTF???? Why aren't these parts a more durable metal, since this is one of the most expensive and supposedly best built cars you can buy.

GSteg

iTrader: (15)

Number one reason why plastic chain guides fail is because of improper chain tension. The older 20R wasn't more durable because it had metal guides, it was because they were running double row chains. The same year Toyota switched to plastic guides (1983), they also switched to single row chains. They eventually stretched more than what the tensioner could accommodate so the chain would bang against the guides. Of course once people see the plastic parts shattered, they attributed the problem being the plastic itself, rather than what caused the failure in the first place.

When done right, plastic guides are not bad. There are plenty of engines out there without failures.

Toys4RJill

+1 I agree.

Plastic parts can be just as durable and last just as long as metal. It is very dependent on the design.

mmarshall

Well, as I see it, whatever the reason, if the plastic guides weakened and broke because the metal chains started banging against them, it's obvious which is the more durable of the two.