1963 and newer (maybe 1981) Cadillac timing chain replacements

[Scot Minesinger]

Cadillac started using nylon coated aluminum cam gears in 1963 and used them throughout the years up until 1981 I think (last year of the 368, which was the 472 architecture).  As we all have written, these timing chains should be replaced because the nylon teeth chip away and the aluminum is exposed and cannot handle the steel chain, and if the sprocket fails your amazing 390(1963 only), 429, 472, 500, 425, or 368 engine could be ruined.

I have replaced 5 of them over the years in 472 and 500 engines.  None of them were in super bad shape fortunately, but two seem to be not good.

That changed, last week when I replaced a chain on a 1965 Cadillac 429 engine.  Here is a picture of the teeth of the cam sprocket, all of the nylon was gone and the aluminum cam sprocket was getting ready to fail.  Where does the nylon coating go you ask? Look at the second picture, although most of it was in the oil pan.  One little nylon chip gets sucked up by the oil pick up and the oil pump stops and you loose your engine.  This 1965 Cadillac 429 had 3 more miles left on it if the chain had not been replaced before the engine became a boat anchor.

Just a reminder - replace your timing chain if it is original. 

A real good American made timing chain set is about $60, and a cheap one is $50, so please buy the good one.  You have to reseal the front of the engine and that kit is about $40, so $100 all in for parts.  The labor is the killer, water pump, fuel pump, oil pump, front engine cover, harmonic balancer, oil pan, center link, flywheel cover, exhaust Y pipe and oil pan all have to come of to properly do the job.  On FWD Cadillacs you have to pull the engine to get the oil pan off, and there is a way that is less desirable to not remove the oil pan and keep engine in FWD Cadillacs of this era (1967-1981). 

During this process there all the might as wells too.  Might as well detail the oil pan, might as well replace the fuel pump, and etc.

[Dan LeBlanc]

It's not just a Cadillac problem.  Ford did the same thing with their engines.  My 77 Connie has the 460 and I'm unsure at this point if the timing chain has been done.  It's almost as bad of a job on the Ford.

[Jason Edge]

Scot is correct. I have broken down over 50 1963/64 390/429 engines and often the nylon coating often starting to chip off or completely chip off. I have attached 2 pictures showing the 2 extremes. Sometimes the are very nice, almost perfect, even on higher mileage (125K to 150K  mile) engines, and sometimes almost gone on lower mileage (< 100K mile) engines. I have attached 2 examples showing the two extremes. When I pop the front cover off the next engine and see all the nylon coating I tend to believe it is a healthier engine block vs a similar looking engine with most of the nylon off.   Once the nylon starts to chip off, it is an invitation for disaster. The oil pickup pipe and screen will filter the larger chunks but smaller pieces can make their way through the wire screen, and I have seen the wire screen compromised, perhaps by something else, leaving small gaps for bigger pieces to work their way into the oil pump and get churned through the engine. Bottom line, changing out the timing chain and gear set is good insurance and will often improve overall performance if nylon had already started coming off leaving you with a loose timing chain.
One final note:  On the 1963/64 390/429 engines the oil pan does not have to come off to remove the front cover after the balancer is off. There are 2 studs at both front corners of the oil pan that screw into the bottom of the front engine cover and go through the very front of the oil pan.  Thes studs prevent you from removing the front engine cover when all other front cover bolts at removed.  You can screw two 1/2" hex nuts back to back, tighten, then back the stud out, and remove the front cover leaving the oil pan in placed. Getting the front gasket on the pan to seat may require loosening the oil pan a tad to slightly drop the front and then tighten back up against the front oil pan to front cover gasket, however, I have installed a couple of front covers without touching any of the other oil pan bolts. This is for the 63/64's only. I am a dummy when it comes to other years.

[Caddyholic]

When I did the engine reseal on my 62 I was supprised to find a aluminum nylon gear. Is is a 56k car so they must have been starting to use them in 62. It was in good shape but I put a new set in.

["Cadillac Kid" Greg Surfas 15364]

FWIW,
First of all shouldn't this thread be in the "Tech" section?
Secondly, you CAN pull the front cover on 472/500/425/368 motors without removing the pan, the exhaust and lowering the drag link.  This applies also to the FWD cars so in that case it is quite a labor saver.
You do this by tapping the two dowels inward until the front cover is clear, then the cover can be angled off.  Resealing is a bit of a chore, but in the long run if it is done carefully, there will be no difference in the results.

The dowels (after the front cover is removed) are driven in and carefully caught, to be inserted into the block through the front cover after it is replaced (threaded over the crank snout and over the front lip of the oil pan).
I have done this both ways quite a few times and if the motor is not coming out for other reasons I would prefer the non-pan removal method.
Greg Surfas

PS: What I have done is buy a supply of these dowels so that I can insert new ones when I do this project

[savemy67]

Hello All,

While there is a Rockwell hardness scale for plastics, and a Rockwell hardness scale for metals, a cursory search failed to find any correlation values.

I would like to know why Cadillac engineers thought it would be a good idea to have a steel chain mesh with a nylon covered gear.  How much engine noise did this combination really abate?  A steel cam gear would have been less expensive, and perhaps more durable.

The nylon on my '67's cam gear is intact for now.  I have a bore-scope/camera, so I hope to get images from time to time, and keep an eye on things.

Christopher Winter

[WTL]

Its true that you dont have to drop the pan on 472/500 class, but it is a real PITA to get it to seal without leaking.   At least it was on mine.  If I had duel exhaust, I would have definitely dropped it.  When I redo my exhaust, I was actually wondering if I couldnt move it so that the pan can be dropped more easily.  Im sure there is a way. 

["Cadillac Kid" Greg Surfas 15364]

"I would like to know why Cadillac engineers thought it would be a good idea to have a steel chain mesh with a nylon covered gear.  How much engine noise did this combination really abate?  A steel cam gear would have been less expensive, and perhaps more durable."


Because it was measurably (who knows how much) quieter.
The Nylon was supposed to need les lubrication. Besides the nylon is typically good for 150-200,000 miles if used continuously. That was considered an automotive lifetime.
Greg Surfas

[cadillactim]

Just to add to Jason's tip on removing the front covers. I only remove one bottom stud the way Jason said. Then you can slightly  turn the cover and lift it off of the oil pan. This trick works on 63-67 models.

Tim

[cadillacmike68]

Replacement timing gear sets seem to be all metal - no more nylon capped gears.

[TJ Hopland]

I suspect if you wanted a plastic set you would have had to get one from a dealer.  I doubt aftermarket ever made em out of plastic so once GM discontinued the part that was it.

I'm surprised to hear they did that back all the way to 62/63.   You would not think they would have trusted the plastics back then for that type of load and environment.  I suppose it could have been WW2 tech that had been 'proven' by 63?

[Jason Edge]

Just to add to Jason's tip on removing the front covers. I only remove one bottom stud the way Jason said. Then you can slightly  turn the cover and lift it off of the oil pan. This trick works on 63-67 models.

Tim

Never thought of that... good info. Once you have the two 1/2" wrenches in hand and nuts tightened together and stud from one side out, it only takes a couple more minutes to back out the other side stud. I always like to chase the stud threads with the die anyway, but cool to know you can just tilt cover with one stud out.

[Scot Minesinger]

It is true, and I have done it on a 1972 FWD Cadillac 500 engine Eldorado (and a friend did on a 472 RWD 1970 Cadillac) the front cover can be removed without dropping the pan.  You can even catch with your hand (using two people) the dowels or just make your own, they are 5/16" stock.

However, given that there was no teeth left on this cam sprocket, it is essential in this case to drop the pan and clean out the nylon scraps.  The other benefit is that the rear main seal can be replaced with oil pan dropped, and these almost always leak.  In RWD the engine does not need to be pulled (hood removal too) to drop the pan.

There was a discussion on this forum previously asking about the nylon coated sprocket and 1962 was the answer for last year of the all metal timing chain/gear set.  I trusted that, and so basically any year with a nylon coated sprocket should be replaced if original.

Yes, Lincoln, Ford, and other manufacturers used the nylon coated sprocket during the same era.  My Dad lost a timing chain on his 1970 Oldsmobile 442 convertible with the 455 engine.  Fortunately the car would not start, and it was not a failure while running issue.  Guessing that was a nylon coated cam sprocket issue too.

[TJ Hopland]

The 472 family of engines also had the same nylon sort of material on the valve guide seals that often also ends up in the pan/pickup tube.    They get plenty brittle with age but in theory don't get any contact so I'm not sure what causes them to break off.  Must just be heat cycles and vibration.