My 84 has its original chain and gears at 150,000 miles. Should I plan on changing it? Does anyone know if the 84 has nylon covering on the gear teeth which are prone to wear faster?

 

I honestly don't know if these are nylon or not... if they are not (which someone will confirm), I would not bother... the motor will need rebuilt soon enough (175k or higher), so I wouldn't dig in to fix what more than likely is a-ok.

 

They are nylon. But that doesn't mean they wear faster. The nylon teeth are prone to breaking or chipping which can lead to excess play in the timing set. First, check for play. It is isn't excessive, wait until overhaul time. I changed mine at approx 150,000 miles and all the nylon teeth were intact and not badly worn. If I hadn't already expended the labor to change it, I would have left it alone. I had 12° play, but it was all just timing chain stretch.

RACE ON!!!

 

What CFI said. It's unusual for one to break, but they do stretch over time. When they stretch, you lose timing advance, and thus low end power. I changed mine at 141K and noticed a world of difference in how the car ran afterward. It had a smoother idle, better vacuum signal, more low end power, better fuel economy, and just sounded better. But the cam gear wasn't missing any teeth.

But I sorta had to do it. The harmonic balancer let go and the outer half did a number on the timing cover oil seal. Since the cover had to come off anyway, I figured it was a good time to do the timing chain.

If you want a general idea of how much slop is in your timing chain, pull the distributor cap off and turn the engine by hand until the rotor moves. Move it to where the pointer and timing scale are centered, and then rotate it backwards. Note how many degrees until the rotor turns the other direction. Divide this number by two and that's how many degrees of base timing you're losing due to slop in the chain. It's not scientific, but close.

Be advised, it's not a particularly fun job on a C4, but it's not rocket science either. My back kept reminding me I'm not 21 any more.

If you're planning a rebuild in the near future, I'd hold off on doing it.

 

A couple years ago I jumped in my 84 and turned the key and heard a knocking noise. It was the timing chain. The nylon teeth were vitually gone on the cam gear. The chain had so much play, it was slapping against the timing chain cover. I dropped the oil pan and it was filled with nylon.

I replaced the gears with a Cloyes setup and the car has been golden, not to mention the new found life the car was given with the new gear set.

When I started the car for the first time with the new gear set, I instantly noticed the difference, as FrizleFrak mentioned, better idle, vacuum signal and over all, just a better sound.

With the proper tools, you can do the job in an afternoon, without the proper tools, your looking at an eternity.

If you don't already have a Helms, invest the $90.00 and pick one up.

Good luck.

 

Hmm. The crank gear doesn't have nylon teeth, only the cam gear.
Scott

 

Thanks for the pickup

 

I would say that the average timing chain lasts about 150K miles on a SBC. On my old truck it broke at 160K miles, so I would recommend changing it anyway so it doesnt break at an inconvenient time.