: Anyone remember Camshaft gears with Nylon teeth? 1978 Deville.
07-27-13, 02:42 PM
In the 1970's lots of American cars had camshaft timing gears with Nylon covered teeth. This was done for quieter operation. In time, the nylon would fail, sometimes leading to plugged oil pump pickups, sometimes jumped cam timing.
In my shop days, I only RECALL 1 1978 ford, getting towed in with a 302 that jumped time, due to aforementioned failure.
My brother just bought a 1978 Coupe deVille, 143000 miles. He is going to R&R the water pump. Did his engine come with said nylon gear? Anyone have knowledge or experience with these gears?
I have recommended he R&R the timing set, with the water pump.
07-27-13, 03:14 PM
No idea on the Cadillac engine - I build Olds 455's and will ALWAYS use an all-iron Cloyes double-roller timing set instead of the nylon faced articulated link chain gearset.
Look up an original timing set in www.rockauto.com
07-28-13, 02:08 AM
It wasn't just the 70s car manufacturers used it in the 80s too. Check the play in the chain before changing it. Some engines are more susceptible to those problems them others.
The Ape Man
07-28-13, 09:24 AM
Real Cadillac engines have an oil slinger for the timing chain. I have not seen one fail nor seen problems other lesser brands seem to have.
I have seen people post firsthand accounts of death and destruction. If it's on the internet it must be true.
07-28-13, 11:28 AM
True, the 425 came with this type of timing set, as did the 472, 500, and most likely the 368. The Chevies, Pontiacs and Oldsmobiles seemed to fail more often than the Cadillacs and Buicks, for some reason. Possibly due to the fact these engines did not see the higher rpms the other engines were subject to. Chevies and Pontiacs could fail within the ffirst 120 K miles.The double roller type timing sets were used in the engines designated for trucks, so that limited this use to Chevy and Pontiac. Chevy and Pontiac engines were subject to a lot of cam thrust. Pontiac incorporated a thrust plate, but it still did not keep the cam gear from wear.
Remember the 79 LTD II that chewed up the plastic teeth in NC! Others from memory: 67 Pontiac 400, 68 Pontiac 350, early 70's Chevy 307(?), 69 Ford 302, 72 Ford 302, 83 Buick w/Olds 307, others lost in time now. Do remember a 70 Pontiac Grand Prix 455 losing it's teeth too. The pre-interference engines were not the disaster that the later interference engines were. The LTD happened at highway speed and bent all 16 valves immediately. I replaced them with steel cam gears and new chains wherever I found them --first, if possible. Cad 500 never let go and had 150k.
The Ape Man
07-28-13, 05:29 PM
The Cadillac engine was a much more modern design than Chevy, Olds, Poontiac and Bu-ick. The Cad 472 was an improvement of the Big Block Chrysler and had the benefit of quite a few years of seeing what held together.
07-28-13, 07:18 PM
I'm 99% sure the Cad 425 has plastic gears. I have replaced them on Chevys and Oldsmobiles with the plastic broken off the teeth and the engines still ran decent. 140k and 35 years should be enough miles for the plastic to be falling off the gears. I am still on the fence on if I would go through the extra work to replace it if the car was running fine. It would definitely be nice to replace it but you may or may not have to remove the radiator to get room to get the harmonic balancer off. Once you break the oil pan to block seal and the timing cover to oil pan seal, it is tricky getting it sealed back up again. You could very well end up with a minor leak.
I honestly don't know which way I would jump. I guess it would depend on how I planned to use the car. If the car is never going to go more than 100 miles from home I might leave it alone. If I planned to drive the car long distances, then it would be best to have that timing chain taken care of.
07-28-13, 08:37 PM
I believe the 425 will have the plastic gears too.
Pic from a 454 for reference, unknown miles, ran fine. The cadillac 500 had one that was in good shape, unknown miles.
I have seen, replaced and curse those nylon gears, but can't say what the '78 had, but if I where betting, I'd lay my money down on the #$%^&* nylon gear.
07-29-13, 04:19 PM
SO..................it sounds like my Brother's 1978 Coupe HAS a nylon cam gear. Also, the OIL PAN GASKET, must be disturbed to R&R the timing chain set.
07-29-13, 06:21 PM
It does but you will won't to try to get the crankshaft hub off first. They seize on and have to be cut off sometimes. Not sure if yours will have it but I think it does.