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Couple years ago....Probably the same reason Sears started using plastic gears in their drills......To save money and to get you to buy another one when they melt ....John........:banghead3 :banghead3 :banghead3 :banghead3 :banghead3 :banghead3
 

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In the 90's...They works really well, make for a quieter valvetrain, cost less to make, result in less heat,, etc. Ive never seen one fail in a normal application.
 

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They're OK as long as everything is OK. As soon as the engine is overheated and/or run low on oil, they're history.
 

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They're OK as long as everything is OK. As soon as the engine is overheated and/or run low on oil, they're history.
But even with a metal cam..overheat the engine, run it low on oil...just a matter of time....
 

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I can,t wait to see a plastic engine.imagine a foot long flame.blue.just coat it with .? light to handle. no more hernia,s.
 

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Recall that back in the day on OHV engines, there were two ways to drive the camshaft off a the crankshaft (car engines). One was a hy-vo chain, the other was a set of helical cut gears, in which the crank gear was steel and the cam sprocket driven gear was aluminum with a plastic fiber rim shrunk onto it (ivory inb color), which had the teeth that engaged the crank gear. This was common on straight sixes, most V8 engines used the hy-vo chain. This quieted down the engine.

Later they went with double roller chains and belts which carried over to the OHC designs.

A few engines (like the Porche 914-also the VW vanagon waterboxer) used steel to steel helical cut gear crank to camshaft drives.
 

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GM used a metal hub and a phenolic cam gear in their small blocks for a few decades...fact is they worked and worked well...My cousins 90 Sierra had one and it went 330,000 miles and showed minimal wear when it was replaced.
 

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Ford already made a plastic engine...literally, a plastic engine.

2.3 Liter engine, 318hp, 14,000 rpm redline.

Pinto crank, plastic block, plastic rods, plastic pistons with metal crowns, plastic head with metal combustion chamber, plastic cam...whole engine, dressed and ready to run was 153 lbs.

They used Torlon Thermoplastic
 

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Recall that back in the day on OHV engines, there were two ways to drive the camshaft off a the crankshaft (car engines). One was a hy-vo chain, the other was a set of helical cut gears, in which the crank gear was steel and the cam sprocket driven gear was aluminum with a plastic fiber rim shrunk onto it (ivory inb color), which had the teeth that engaged the crank gear. This was common on straight sixes, most V8 engines used the hy-vo chain. This quieted down the engine.

Later they went with double roller chains and belts which carried over to the OHC designs.

A few engines (like the Porche 914-also the VW vanagon waterboxer) used steel to steel helical cut gear crank to camshaft drives.
True I had a Chrysler slant six that had plastic cam gears and a 318 V8 that did also and they never gave me a lick of trouble so the technology does work.

No reason for it not to if you take care of it.

Ron
 

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I hate timing gears made of anything BUT metal!...had 2 Chevy sixes strip all the teeth of the fiber cam gears,one in my 1956 pickup's 235 six did it 35 miles from home,and so did one in a 250 six I had...it was **** to replace them too,as the cam HAD to be removed and brought to a machine shop to have the gear pressed on and off...that was funmremoving the grille and radiator from a 50 year old truck!..the 235 was one from a fleet that ran on propane,and the insides of it were immaculate too--while the 250 looked like it had roofing tar for motor oil most of its life--both lost the teeth on the can gear in just one spot ,and the rest of the teeth were OK,which I thought was kind of strange..

I had many small block Chevy's with the "nylon" cam gears,when I took them apart I'd almost always find NO nylon on the teeth,and badly "hooked" aluminum teeth was all that was driving the chain,and the nylon teeth all ended up in the oil pump and blocked the screen to it..I tossed them and put Cloyes double roller chains and gears in them,so I could trust the engine on long trips!...I did use one new nylon cam gear I had given to me in a 229 V6 I didn't plan on driving too far or keep long though....they last maybe 45-100K,then they fail,and the hotter the climate the sooner they will fail..

I dont like it when manufactuers use cheap plastic crap to build parts that should be metal,at least die cast,like intakes ,its just another thing that will fail way too soon and usally with disaterous results--certainly dont do much for a companys "good reputation" building things from plastic junk...there out to be a law!..
 

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I hate timing gears made of anything BUT metal!...had 2 Chevy sixes strip all the teeth of the fiber cam gears,one in my 1956 pickup's 235 six did it 35 miles from home,and so did one in a 250 six I had...it was **** to replace them too,as the cam HAD to be removed and brought to a machine shop to have the gear pressed on and off...that was funmremoving the grille and radiator from a 50 year old truck!..the 235 was one from a fleet that ran on propane,and the insides of it were immaculate too--while the 250 looked like it had roofing tar for motor oil most of its life--both lost the teeth on the can gear in just one spot ,and the rest of the teeth were OK,which I thought was kind of strange..

I had many small block Chevy's with the "nylon" cam gears,when I took them apart I'd almost always find NO nylon on the teeth,and badly "hooked" aluminum teeth was all that was driving the chain,and the nylon teeth all ended up in the oil pump and blocked the screen to it..I tossed them and put Cloyes double roller chains and gears in them,so I could trust the engine on long trips!...I did use one new nylon cam gear I had given to me in a 229 V6 I didn't plan on driving too far or keep long though....they last maybe 45-100K,then they fail,and the hotter the climate the sooner they will fail..

I dont like it when manufactuers use cheap plastic crap to build parts that should be metal,at least die cast,like intakes ,its just another thing that will fail way too soon and usally with disaterous results--certainly dont do much for a companys "good reputation" building things from plastic junk...there out to be a law!..
Its a shame you had such bad luck with them, the general concensus is that they will last the life of the engine or at least the timing chain.

My 85 vette, that regularly saw high rpms, long service intervals, high engine temps, over 240*...the gear was pristine when the engine ran out of oil and spun the mains...In fact the timing chain had very little slack and I attribute thatto worn cam bearings. Plastic gear, didnt have a mark on it.

I tore down an 86 K2500 Sierra that had 281 or 381K miles on it, used oil, knocked...but had good oil pressure, but no power..the cylinders were worn over .020 out of round...But the plastic timing gear, showed no wear, chain was stretched and loose, but the gear were not hooked or worn.

I told you about my Cousins 90 Sierra...

My boss who was ASE certified and been working on cars since the early 70's said he'd never seen a plastic timing gear fail in a situation where the chain was not so badly worn that the chain was slapping the cover...

Guess its like Fram oil filters...some people use them exclusively...I used 1...just 1, and it collapsed and my oil pressure went from 65 to 2 @ 2800 rpms...
 

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I dont like Fram filters either--but have used up some freebies I got,and haven't lost an engine yet...all engines should have a by pass valve so the bearings wont starve,should an oil filter clog up or collapse,so I dont see how Fram gets the blame so often for that happening,unless that valve was stuck and failed to function..

Must be my good luck or a MA thing,as far as nylon and fiber cam gears failing so often,I have seen probably a hundred with no nylon teeth left,or fiber ones that failed in my day...I think GM shot themselves in the foot by using plastic intakes and other "critical" engine parts...I thought I'd seen everything the other day,when a friend showed me a distributor from a 4.3 V6 in an S-10--the entire thing is made of PLASTIC,and it dont even have a brass bushing for the shaft in it either!..the thing was so egg shaped the truck barely could run!...I thought cast aluminum distrubutors were bad enough!..geeez!..

Most of todays engines are not much more durable than plastic either--overheat one just and chances are good its JUNK..I tolda guy who runs a pizza shop that his Cavalier wasn't worth fixing after he drove it home 20 miles with very little coolant keft after it boiled over--said "its just like a pizza--overheat it once and its NO GOOD!"..
I can remember driving straight sixes with no coolant till they turned orange,and refused to shut off when I turned the key off,yet the next day I could fill it back up and drive like nothing happened,at most I'd need a head gasket or radiator!...guess those days are gne--.
 

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My Mustang has a plastic intake and coolant crossover tube, 184K miles and so far so good.

My 98 Ram I just sold, overheated once from a busted radiator, pegged the gauge past 260...didnt hurt it, that was at about 140K miles. Then at 220K miles it lost the lower radiator hose, engine got so hot that the valve covers, block, etc..smoked. The engine was detonating at idle. It got so hot that when it started to cool down and I got water in it, the engine was TIGHT and almost didnt want to turn over..but it did, and ran good. I actually didnt have any problems after that, and sold it with 226K on it, using 3/4qt evert 3K miles..haha
 

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I haven't had much problem with nylon cam sprocket teeth either, but in every case, a double row timing chain and matching crank and cam sprockets replaced them (its not an expensive upgrade ..<$100 upgrade typically). I have had more cases of timing jumping due to the hy-vo chain jumping a tooth, disabling the vehicle (FORD 302 in 70 coupe was the last time). It was in the garage, and had 120,000 miles, and moved back about 10 feet and died, then cranked funny. Good ole ******, she was a trooper none the less. Ford used a nylon ring with teeth even with the hy-vo, and that did increase the life of the assembly, since the chain developed too much slack.

On Fram filters, the worse thing you can do is drill out and chamfer oil galleries, install a HV Mellings oil pump, match holes in mated assemblies, block off the lifter galleries and convert to either solid lifters or roller cam, and then use a FRAM filter. The pressure drop through one of those is considerable, even when they are 'good to go'. I use NAPA GOLD filters in the 428 CJ and 289 GT engines.

I like those engines, but love my filterless Briggs Twin.:bannana:
 

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I dont like it when manufactuers use cheap plastic crap to build parts that should be metal,at least die cast,like intakes ,its just another thing that will fail way too soon and usally with disaterous results--certainly dont do much for a companys "good reputation" building things from plastic junk...there out to be a law!..

Right there with ya. I hate having to fix plastic parts that shoulda been made of steel from the start. Told dad a few years ago we would start seeing more cheap and worthless plastics used where they don't belong. Gms pastic gears and jeeps plastic valve covers both should have gotten somebody fired.
 

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Yeah the L/C Kawi's are the only instance of broken plastic cams Ive ever seen...weird.

I have seen a number of failed Honda GC OHC camshafts, but in every instance the engine had been run low on oil, nearly out of oil, or at high speeds for extended periods of time...
 
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