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
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
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
Quote from: "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.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
Boy, the Crank gear teeth are worn.
Bruce. >:D
Also looks like oil changes lagged a bit.
:o
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
Now that you have checked it, are you going to keep in service for
another 50k or till it fails? Bruce Roe
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
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.
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.
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
The wear and cracks on that timing set only confirm it has no place
in any of my engines. Bruce Roe
Hey, that looks like my old cam gear!
http://forums.cadillaclasalleclub.org/index.php?topic=154660.msg425803#msg425803
:)
Quote from: "Cadillac Kid" Greg Surfas 15364 on February 17, 2020, 06:05:01 PM
....... 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. >:D
Here is what my gear looked like after ~51k miles:
(https://forums.cadillaclasalle.club/proxy.php?request=http%3A%2F%2Fjelloslug.com%2Fcaddy%2FIMG_5235.JPG&hash=a1f897e2354cab00a4b4ae22960ea83b2d826098)
(https://forums.cadillaclasalle.club/proxy.php?request=http%3A%2F%2Fjelloslug.com%2Fcaddy%2FIMG_5236.JPG&hash=629f08b0b798de13e7bd06ff80f3fb1339b9d186)
(https://forums.cadillaclasalle.club/proxy.php?request=http%3A%2F%2Fjelloslug.com%2Fcaddy%2FIMG_5258.JPG&hash=45e5df99701e1ad69fd9cbe30d657e759466191e)
The gear looked relatively OK but the chain was worn out and there were a few crack here and there.
This was mine after God knows how many miles.
And I found all the plastic pieces inside the oil pump pickup screen.
Bruce. >:D
Bruce wins!
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
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
That's true, and it would also help generate service related revenue from the recommended service requirements to maintain the warranty, if said warranty lasted long enough.
Quote from: bcroe on February 18, 2020, 03:31:19 PM
........ and it helps force purchase of new vehicles when a major repair is needed on an older vehicle. Bruce Roe
The theory of "Planned Obsolescence".
Plus, the Factory really didn't care if they broke up after the Warranty Period ran out. These combinations would have been tested till destruction, and deemed to be good enough for production. Remember the old Fibre Gears in a Chev inline 6. They lasted for years, and yes, I had one strip, 60 miles from home.
The "Morse Chain" lasted for a long time, until it stretched that much that it flogged out a hole in the timing chain cover, and the engine lost oil. I rebuilt a SBC engine which had the hole in the timing cover from chain slop.
Bruce. >:D
Not to defend anyone because that is not my responsibility, but the 472/500 inch motors as well as the 429's were probably the most engineered/tested/tortured and revised engines of their era. They were tested in real driving tests for 100's of thousands of miles, and any element that did not hold up was revised and refined or replaced. Now this was in a time where the average time the first owner kept a car was about 3 years and at 10 years old (my 72 eldorado had a listed value of about $500 in 1982) cars were considered past their useful life. No one contested that fact.
The one thing the engineers could not test was the actual weathering of components buy the years and unfortunately the Nylon gear coating deteriorated over a 20 year or 120,000 mile period. Well beyond what it was expected to do. I really do not think that planned obsolescence was on their mind when they went to the high Nickle cast iron block and set up all the tolerances and clearances that resulted in a motor that "with proper maintenance" would wear at the rate of 0.001 per 100, 000 miles and after 300,000 miles would stop wearing.
I got 500K out of the motor in my eldo and at 400,000 I pulled the heads to replace a broken valve spring and found that there was not enough wear to catch a fingernail on the cylinder ridge.
It was just an attempt to lower valve train noise. Think about it, a cast iron (like the re[placements) cam gear HAS to be cheaper than the Aluminum gear with the (then) added Nylon casting.
Greg Surfas
Makes a lot more sense than planned obsolescence using more expensive parts that will fail sooner than the cheaper parts.
QuoteUsually you begin to see the timing marking "flutter" during timing
What does "flutter" mean?
Are there any other signs or symptoms of timing gear/chain wear without having to open up the front of the engine to visually inspect it?
Quote from: Bentley on February 20, 2020, 07:01:16 PM
What does "flutter" mean?
Are there any other signs or symptoms of timing gear/chain wear without having to open up the front of the engine to visually inspect it?
What he's referring to is when you are checking the timing, the mark jumps around from the slack in the chain. It allows the cam to "bounce" back and forth as the chain tightens then goes slack as the load varies on the chain. Basically the mark "flutters" back and forth.
Rick
Here is the cam sprocket off a 1965 Cadillac with 125k miles. The nylon was completely gone and the pieces were all over, including under rocker arm covers. To me this engine had another 50 miles left.
If I have the engine cover off, and the timing set is like $60, I would go ahead and replace it.
The 118k miles 472 cam sprocket is in amazing shape - never seen one that nice with that much mileage.
Scott,
That is why I went to post with it.
Greg Surfas
The 1964 and 1965 cam sprockets and chains were more expensive to manufacture than the 66 and newer because there was more surface area. The 64 and 65 are nine links wide (4 and 5) and the 66 and newer are just 7 (3 and 4). I would have thought the 65 would have been in better shape, but maybe the nylon was improved in 1966.
Greg, thanks for posting, that is very unusual.