Install Nailhead Steel Cam Gear or OEM Nylon/Aluminum Gear?

Just about ready to do my install of timing gear/chain set. Egge tells me I can get the OEM plastic teeth/aluminum cam gear in the set or go with an all steel one. However the OEM one makes the engine run noticeably quieter than going the all steel gear route.

My question is has anyone done one and or the other in their install and what did you find?

Some rebuilders claim that the plastic teeth get brittle and end up in the pan. Now how long does that take and how many miles?

Furthermore, how does one go about determining that a timing chain and gears should be replaced by just looking at them?

Any input would be appreciated.

Those darn nylon coated cam gears should be outlawed in my opinion. Guaranteed premature future problem verses a steel or cast gear. The only time the sight noise increase of a metal gear is potentially heard is in the garage with the door closed and all the car windows down. You'll never notice it with the car humming down the road at over 50 mph., maybe not even at 30 mph.

On all my Pontiac engines I have replaced the plastic coated aluminum gears with double roller timing chain sets. I cannot tell the difference as far as noise is concerned. I can tell you that the double rollers will last the life of a rebuild and stand up much better to stick shift cars. Pontiac's (traditional REAL Pontiac engines) when equipped from the factory with the nylon coated gears would give you trouble in most cases at around 75,000 miles, some cases at 35,000 miles. Sometimes if you were lucky you could hear the chains slap the side of the timing cover before the chain would jump and give you time to replace a set. In any case the other problem with nylon coated aluminum was at the end of it's short life you couldn't just pull the timing cover and replace with a new gear because all that worn plastic was in your oil pan so the pan had to come off to get the plastic out.

On the Pontiac four cylinder engine (61-63 Tempest) which is the right bank of the 389 V-8 the factory used a heavy duty double roller from the start because the four cylinder was so big and vibrated so because it did not have a balance shaft. If the plastic gears were used in this engine it would have a very short life due to the harmonic vibrations which would tear up the plastic gear. The part # for the four cylinder was the same # as the Super Duty 389-421 race engines.

I hope this answere your question.

Don

I have been told and have replaced timing chains on other 60 and early 70 V8's when they broke and it seemed to be around the 60,000 mile mark. Got into the car and no start. That's how I would find out about a broken timing chain or sprocket. Never had one break on me while driving though.

With these high top puncher pistons in the stock nailhead at 10:1 compression if the sprocket broke then the valves would not open and if they stayed closed then no problem, but if for some reason a valve would stay open, then you could potentially have sudden impact with the piston head. I wonder if this would be a real possibility?? Also if the plastic did get into the system is is relatively soft would get caught in the filter screen of the pump and the oil filter. Even if it did go up against tempered internal engine parts it would'nt even win a shouting match not alone scar the internals ... so I would think. Any comments?

Nylon particles from coated aluminum timing gears have been known to take out more oil pumps than anyone wants to know about. Yeah, those particles can and do somehow sneak passed pickup screens.

I doubt if there would be a problem with valves kissing pistons in your engine under any circumstance. The worst two domestically produced engines for doing that were the Lincoln/Edsel/Mercury 383, 361, and 430 MEL block engines along with the Chevy 348/409 engines both introduced in 1958, and were of very similar design having their firing chambers in the block and not the head. In other words they were actually valve in head flat heads which made them potentially an "interference" engine like many of the Japanese engines.

I would NEVER put back any new nylon plastic timing gears

Over the years I have replaced a dozen of these failed gears.

Never really heard any more noise with the steel gear/chain set-up.

If you can find a double-row true roller performance timing sprocket & chain set that would be the very best in my opinion also !

Hey I hear you guys. However, it is my understanding that these gears are all aluminum, it is just that the tips are coated with a very high impact wear resin that lasts up to around 40,000-60,000 miles or more with normal driving as my Roadmaster is a cruise mobile or a highway car. No slam revs or redline line-locking take offs for my Roadmaster.

All I can see is here is if the resin chips off it may go into the pan but would be restricted and picked up by either the oil filter or oil pump screen. As far as the resin plastic going man to man with any of the internal hardened parts it will lose the match as plastic is soft.

I have a timing set with the OEM plastic coated/Aluminum cam gear and chain that I can install. Now one point is Aluminum is not as strong as iron I am told when it comes to gear teeth that is. This may or may not be true but look at all the drives on belt driven charger systems which I believe are all aluminum. Dragsters use this setup with 2000 horsepower.

But if it is true then an aluminum gear tooth could break causing the chain to go off track and then cause valve train/piston damage. But I do not know how high of an occurrence this would be or has historically been. It would be neat to find some service records of an old dealership and see if these coated timing gears were a real problem or not.

Now Buick engineered the engine to be balanced, smooth and quiet. Buick and Cadillac were the only GM engines to be balanced and blueprinted by the factory in those days. This aluminum gear is less rotating centrifugal mass, just like in an aluminum flywheel for faster revs. These facts could of by Buick engineering standards, led them to use the aluminum gear with the coated resin plastic material on the gear teeth for these concerns and others.

The Buick engine was noted as being very dependable. Is there any retired Buick mechanics out there that worked at dealerships back in the day, that could come forward and give some advice and story telling regarding this topic?

Hey I hear you guys. .

Now Buick engineered the engine to be balanced, smooth and quiet. Buick and Cadillac were the only GM engines to be balanced and blueprinted by the factory in those days. This aluminum gear is less rotating centrifugal mass, just like in an aluminum flywheel for faster revs. These facts could of by Buick engineering standards, led them to use the aluminum gear with the coated resin plastic material on the gear teeth for these concerns and others.

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All GM divisions engines were and are balanced, they would simply Not live otherwise!. As far as blueprinting goes I have seen Buick and Cadillac engines where cylinder head chamber volume varies slightly just like all other divisions , plus those engines cylinder heads were never port gasket matched or the ports were never put on a flow bench--which is all part of a blueprint job. As far as the gear goes --it is so small compaired to a flywheel that it would not make any difference weight wise. Listen to Jim Edwards when he tells you about that plastic getting past the oil pump pick up and getting into the pump and bearings, He is not just saying that for conversation, it's the truth. I have been in the automotive business over 40+ years and have seen it too.

Don

I've owned about 15 nailheads (all with no problems requiring engine teardown with up to 100,000 miles on them other than a '63 Riviera 401 that I bought to restore with a locked up engine where a broken piston when into the block) I bought a used 401 and rebuilt it using GM parts except the timing gear ( I installed the all steel replacement along with the matching chain and crank gear), and did that because of experience in a Chevy dealership that I worked in.

We saw quite a few engines in other makes with the 'nylon' coated gears in them, and took in all GM makes and some other makes, and the 'chewed up' plastic created a lot of extra 'cleanup' work and resulting parts and labor costs. There were many GM (and probably other makes) that used the coated gears, and extra work required in cleaning up the result of stripped teeth taught a few mechanics to definately use steel replacements.

I know that earlier 6 cyl. Chevys had the 'nylon' gears in cars and the iron or steel in trucks. If I were rebuilding your engine today I'd definately go with the replacement steel cam gear. You wo'nt notice any noise level difference I'll bet.

kaycee

Age will do them in, in addition to mileage. Below is the one removed from my 70,000 original mile 1971 GMC two years ago:

With the intent of using my truck to haul trailers on long trips, I got to thinking about it having the nylon gear and just decided to replace it as a preventative measure. Glad I did. It's cracked all the way around, as they get brittle with age.

Steel gears are the way to go. You can't hear the difference. Additionally, it was once explained to me that nylon gears were a cost saving alternative to steel gears (makes sense, right? -- manufacturers are occasionally known to push quality to the side for the sake of profits....). While it seems like an elaborate way to make a gear, it's a lot faster to machine or mold the teeth from nylon than it is to cut a steel blank.

(Edit to add): By the way -- that stuff about he nylon chips being harmless.... those chips clogging the pick-up screen on 1960's era Lincoln's have been known to toast engines.

Just trying to see what Depth of knowledge in this regard is out there rather than just getting opinions.

My opinion on cost saving issues for Buick in 1957 as compared to 1971 when plastic started to rule the world are at opposite poles. Buick had just about practically and totally engineered a new car from anything it had before in 1957. A lot of firsts in this car. I believe these plastic gears were an attempt to improve overall performance and drive ability of the car rather than attempting to cut corners. I don't think that was in the mindset of Buick when they put this engine out what with the serious approach of mounting the engine and tilting it etc, etc.... as they did for overall resonance and balance.

You guys are great and have given me real world experiences and that is what I have been looking for. I mean that is what this board is about right?

I just bought my Buick this past spring and I am in the process of a complete service of the motor. The cam gear is NOS that I have on my shelf and could be anywhere between 25-40 years old. So what effect does part n package aging have on the brittleness of the plastic teeth overlay - that too could be a problem from the get go!

If it all goes to hell the cleanup would be a bummer considering I am now just taking my pan off and cleaning everything up, rebuilding my oil pump and installing a 1960 oil filter boss for spin-on filters. I am doing all of this to bring my motor out of it's long term sleep, since my motor has set for at least 30 years that I know of in a garage. Long enough to make black oil look very new and clean looking on the dip stick. Heck it even smelled new, but when I drained it, black as any used oil without of course the fuel smell which evaporated years ago. I also noticed as I slowly turned the drain plug out so I could watch in slow motion what was dripping out before I got the drain plug all the way out, I noticed clear liquid coming out. Maybe a couple table spoons. Like water but very clear. I let it sit like that for a minute or so and let this clear liquid drain out. Then as I turned the plug out toward the end oil started dripping and the clear liquid was gone. I let it drip like this for awhile and noticed no new clear liquid dripping. Then I removed the plug and drained into a container I will take to a guy out at my local airport for an analysis. I don't think the clear fluid was water. There had been no signs of water on the dip stick or even after I drained it water in the oil as milky or viscous. Just dark oil that still felt very lubricating to the finger as I finger tested it. I wonder what the clear liquid was? Of course I have never drained oil from a verified garage kept car that sat for 30-years or so before and do not know what kind of separation chemistries would be involved here. Would anyone car to comment on what this clear liquid was as well?

My opinion on cost saving issues for Buick in 1957 as compared to 1971 when plastic started to rule the world are at opposite poles.

Profits didn't matter in 1957?

This all sounds like a great expenditure of gray matter considering you can just put on a steel gear and be done with it. You just shot down your desire for opinions and followed it up with an opinion. Given your defense of nylon gears, sort of sounds like you've already made up your mind.

Mass/weight reduction/savings could have been one of the objectives along with the gears being quieter.

No you guys are right about the metal gears and the advice about the pros and cons that I did not know about. I like posts that bounce things around a little and since I started this post I reserve the right to do just that.

So I have decided to go with the all metal gears since reading everyone's valued comments.

Yeah I tend use my gray matter from time to time but try not to unless it's needed since I only have so much of that stuff to go around.

Hi Biuck Man,

We older nailhead guys still have some gray matter left inside, and ,in my case , still a lot of still graying hair on top. Good luck with your Buick. You came to the right place!

kaycee

Thanks kaycee. I like learning by listening to peoples stories and explanations on things. Also these forums benefit by the give and take presented. I am in my mid 50's and have been a car guy my entire life and will continue to be until I am too stiff to stand or even roll over!