Timing set with 118 K miles

["Cadillac Kid" Greg Surfas 15364]

I just started pulling apart a 1970-472 with 118,000 miles and was amazed at the shape of the nylon on the cam gear. The crank gear and the chain are worn a bit, but there is virtually little slack in the chain and the gear itself has just a few minor cracks.  There has been much said about IMMEDIATELY changing timing sets regardless of the mileage on mid '70 motors, however I would bet this set had at least another 50K in it.
Just observations, not suggestions.
Greg Surfas

[Jeff Rosansky CLC #28373]

Interesting. Would appreciate if you posted a picture of it once it sat in the cleaning tank for a few hours. Would be interesting to see if it is cracked.
Jeff

["Cadillac Kid" Greg Surfas 15364]

Jeff,
I'll do that. I just wanted to shoot a picture EXACTLY as it looked when I pulled the timing cover off. I'll clean up the cam gear and post a shot.  By the way, this is how the cylinders looked.
Greg Surfas

[bcroe]

I just started pulling apart a 1970-472 with 118,000 miles and was amazed at the shape of the nylon on the cam gear. The crank gear and the chain are worn a bit, but there is virtually little slack in the chain and the gear itself has just a few minor cracks.  There has been much said about IMMEDIATELY changing timing sets regardless of the mileage on mid '70 motors, however I would bet this set had at least another 50K in it.Greg Surfas

Yes some are still good, and some chains have fallen off.  I do
recommend checking slack, but even a decent one could fall
apart tomorrow at this age.  Not being a gambler, not wanting
to find out just when the next one fails, I replace them and
the car runs better.  Bruce Roe

[The Tassie Devil(le)]

Boy, the Crank gear teeth are worn.

Bruce.

[chrisntam]

Also looks like oil changes lagged a bit.

["Cadillac Kid" Greg Surfas 15364]

Bruce/Chris,
That is kind of my reason for showing this.  An apparent oil change every 20,000 miles (whether it needs it or not) , a lot of short trips ( the sludge accumulation) a tremendous amount of wear on the crank gear and there still is minimum play on the chain and the cam gear is still intact.  A blanket statement (do this or that without fail) is often untrue, and an actual physical check (cam gear/chain in this case) is well worth the effort.  IMHO
Greg Surfas

[bcroe]

Now that you have checked it, are you going to keep in service for
another 50k or till it fails?  Bruce Roe

["Cadillac Kid" Greg Surfas 15364]

That motor is going to get rebuilt, but IF it was in an operating vehicle and When I visually checked it with an optical device and saw its condition I would first throw up at the condition of the sludge in the motor and then if the motor continued to operate correctly as this one was said to be doing, set it up to check it about every 5-7K. 
Greg Surfas

[fishnjim]

I ask how you actually verified that the top gear was never changed?   
Observed wear should be commensurate with mileage.

They used all metal for decades previous and when they switched, there were problems with life.  Much like early timing belts, aka learning curve.   Once they got the polymer right, they are better in antiwear.   These bigger is better era cars were cost driven designed aka the "disposable" low warranty period, ie, not long lived.   Plus SOA was not where it is today.   They made money selling parts also.     
Usually the chain is what wears and "grows" causing slack.   When they can bend over on their side when held horizontal they're usually shot, cf to new.   Usually you begin to see the timing marking "flutter" during timing.   
Mechanically, the top gear is larger diam. and has a straightening and load distributing effect of the chain where as the crank side is smaller so it's linear speed higher, so there's more differential movement on that end, plus it's supplying the force to drive the top gear.   So one should conclude it would normally wear more.   

[TJ Hopland]

Maybe the sludge preserved the plastic?

I had one that went from no visible cracks to no plastic at all in about a year and 3000 miles.   The car was under 50k when I got it and I suspect it had been sitting for several years then very lightly used then I drove it just about every weekend for a year.

["Cadillac Kid" Greg Surfas 15364]

This is what the gear looks like clean. For those of you that find the missing tooth I broke it when I dropped the gear.
I am not trying to prove ANY point but mechanical expertise is gained through varied experiences and I just wonder how many 472s and 500s went to the crusher in the 80s and 90s with 200k on the clock and good cam gears.
Greg Surfas

[bcroe]

The wear and cracks on that timing set only confirm it has no place
in any of my engines.  Bruce Roe

[hornetball]

Hey, that looks like my old cam gear!

http://forums.cadillaclasalleclub.org/index.php?topic=154660.msg425803#msg425803

[The Tassie Devil(le)]

....... and I just wonder how many 472s and 500s went to the crusher in the 80s and 90s with 200k on the clock and good cam gears.  Greg Surfas   

More than should have.

Bruce.

[MaR]

Here is what my gear looked like after ~51k miles:









The gear looked relatively OK but the chain was worn out and there were a few crack here and there.

[The Tassie Devil(le)]

This was mine after God knows how many miles.

And I found all the plastic pieces inside the oil pump pickup screen.

Bruce.

[hornetball]

Bruce wins!

[Cadman-iac]

Knowing what I know of the nylon gears from personal experience,  anytime I'm into an engine for any reason,  if it has a  nylon gear in it, it doesn't when the I'm done.
I've not ever noticed an appreciable difference in noise between the nylon and the steel gears. I've heard that the only reason why the nylon gears were used was to reduce the noise from the chain. To me it's just not worth the risk to leave one in an engine if you have the opportunity to replace it.
I've seen too many oil pump  screens filled with little pieces of nylon.
Just my opinion.
Rick

[bcroe]

The chain noise excuse is because (like so much of what I hear) they needed
some acceptable justification.  The real reasons (typically being quite unfavorable)
might be its much cheaper to mold a plastic gear, and it helps force purchase of
new vehicles when a major repair is needed on an older vehicle.  Bruce Roe