STRETCHED timing chain???????

[Jrichard]

My 93 1500 silverado,5.0 tbi------developed a miss and was running poorly---the gentleman that does all my work to keep it running -----Brought out that ancient relic called a 'timing light'----after checking,was told that the timing HAD decreased 12-15 degrees! once we were able to loosen the distributor{that was ajob within itself}--advanced the dist. back to it's correct degree,all was WELL ---------the idle smoothed out,my gas mileage went back up{to a whopping 17 per gal.} and overall driveability went back up ------------was told that the TIMING Chain has STRETCHED?????????? only have 188K on the motor---------replacing the said chain,water-pump checking the oil pump-----power-steering hoses need to b replaced!!:mo money::mo money:SOOOO has anyone heard of the 'stretched timing chain' ?????????????????????? I understand what the problems could be IF not taken care of!!!!----------:usa:

[oldandcrotchety]

Absolutely. Sometimes get so stretched that they jump a cog.

[Steve S]

Jrichard

 

A "stretched" timing chain used to be a common problems on earlier automobiles that used a steel chain instead of a belt. The stretching come from both the chain wearing AND the drive gears that it runs on wearing. It wasn't uncommon for an engine with over a 100K to have the timing chain jump a cog on one of the gears, usually the camshaft gear (the cam gear was often aluminum with a nylon cover). This would cause an engine to run real rough and somtimes even bend a valve or two or even 16 :whistling:if the timing was far enough off.

 

If you have that many milles on an engine I would say it is time for some serious maintance. Dig DEEP into that pocketbook and pay quickly before you suffer more engine damage. Re-adjusting the timing is just a stop-gap measure that will only last a short time.

[scotty]

Yes, timming chains can stretch. At 15 degrees it may have already jumped a cog.

The easiest way to check for a bad chain is to lift up the distributer cap, turn the engine backwards by hand a 1/4 turn, mark the crank, then have a helper watch the rotor in the distributeras you carefuly turn the engine forward stopping when the rotor starts to move.

This will give you total wear in the cam system

Over 4 degrees is a lot of wear.

I hope this helps

[jlh3rd]

yep..time for some work

[saddlebum]

very common at one time as was said already they can stretch to the point of jumping teeth Ive even replaced many on early gm's that wolud actually hit the timing cover and wear a hole right through it causing an oil leak.

[GeorgeS]

Hmmmm ?? Seems like pretty good service out of a Chevy motor --

 

Just made last payment on my Chevy Blazer, 62K and plan to keep it on the road a long long time !!!

[Snarley Bill]

My 93 1500 silverado,5.0 tbi------developed a miss and was running poorly---the gentleman that does all my work to keep it running -----Brought out that ancient relic called a 'timing light'----after checking,was told that the timing HAD decreased 12-15 degrees! once we were able to loosen the distributor{that was ajob within itself}--advanced the dist. back to it's correct degree,all was WELL ---------the idle smoothed out,my gas mileage went back up{to a whopping 17 per gal.} and overall driveability went back up ------------was told that the TIMING Chain has STRETCHED?????????? only have 188K on the motor---------replacing the said chain,water-pump checking the oil pump-----power-steering hoses need to b replaced!!:mo money::mo money:SOOOO has anyone heard of the 'stretched timing chain' ?????????????????????? I understand what the problems could be IF not taken care of!!!!----------:usa:

chains don't really stretch, what happens is the link pins and bushings wear. making more clearance and causing the chain to get longer. the reason chains get tight and loose spots if the sprockets have no runout,is the rockwell hardness on the bushings and pins can vary several points from heat treat. there is usually a 2 to 3 point tolerance on rockwell hardness given to the heat treaters. this variation in hardness will cause some pins to wear a little more than others, causing short and long sections of chain.

[jlh3rd]

my 77 monte with the 305 started making a knocking sound ....thought it was a rod but didn't quite act like it....when the motor went, and i pulled the timing cover, i could see where the chain was hitting the cover and almost no teeth ( nylon ) on the cam sprocket....143,000 miles with 3000 mile oil changes.....lesson learned

[Dano]

Had a 67 Tempest with the 326 that would stretch a chain every 6 months. Dial indicated it, changed gears to steel from plastic, nothing did the trick--- finally got another car. Of course, this was in '77....... Shoulda kept it! Along with the 66 Mustang, 72 Satellite Sebring with a 383, the 65 Corvair Corsa w/ 4 bbl, should I keep going!!??

 

Dan

[Snarley Bill]

Had a 67 Tempest with the 326 that would stretch a chain every 6 months. Dial indicated it, changed gears to steel from plastic, nothing did the trick--- finally got another car. Of course, this was in '77....... Shoulda kept it! Along with the 66 Mustang, 72 Satellite Sebring with a 383, the 65 Corvair Corsa w/ 4 bbl, should I keep going!!??

 

Dan

those hi-vo chains that they use on the older design engines are a whole different deal than a roller chain. they create much more sprocket wear do to the gear tooth like meshing of the chain and sprocket. most of the replacement aftermarket cam sprockets were cast iron instead of nylon. all the racers went to rollerchain and sprockets. most of the oem hy-vo chain and aftermarket replacement chain was a pretty low guality soft chain to keep the cost down. i would guess the pins and plates were annealed carbon steel probably around 35 to 40 rockwell, because of the many points of shear compared to a roller chain which the rock well hardness is probably around 55 to 58. i would also think that the pins and side plates on a good high tensil roller chain are made of special metals such as chromemoly. when you think of how small of a diameter a roller pin is on a 630 chain is, and the impact and shear force they get on a drag bike. it's hard to believe they don't break.