Timing Chain and Gear

[Bonnell]

I purchased my '88 with 88K miles and it is my daily driver. I drive 33 miles to work (one-way) and all but 5 miles is interstate. I now have 120K miles.

At what point do I need to worry about having my timing chain and gear replaced? Is this a major job?

 

[WNH]

I am not a mechanic, but I also have an 88 with 119K.
The timing chain is not difficult, but time consuming.
Its about the same as changing the water pump, as its located in back of the WP.
I have the same question about 'when to replace'

 

[Alloydude]

Funny you should metion that. I'm actually in the process of replacing the water pump and timing chain on my 84 that has 134K on the motor. Took me 3 hours to get the water pump off (what a pain in the _$$) Now I'm trying to get the ballancer and timing cover off. I'll let ya know what the timing chain looks like when I get that far. :bang

 

[Alloydude]

OK, Here is what a timing chain looks like after 134k miles. Looked pretty loose and had plastic gears. ??????? I'm sure glad I got that pile of junk outa there. Now its time for a beerGotta put it back together tomarow. Yike's!!!!!!!! http://MyWebPages.comcast.net/ALLOYDUDE/TimingChain.jpg

 

[WNH]

Qyestion:
How do you know if your timing chain needs replacement--Are there any symptoms when it gets loose???
Plastic gears?? Is that the original??

 

[Hrtbeat1]

Checking slack

I don't know about symptoms but if you take your distributor cap off and use a 1/2" breaker bar/ratchet you can check how much slop is in your timing chain. Put the breaker bar/ratchet on the front of the crank shaft and rotate the crank one way then the other and watch the rotor button ... when the button starts to move put a mark on the balancer near the timing check marks ... then go the other way when the button starts to move again mark the balancer and you can tell how much slop you have in the timing chain. I just replaced my water pump and timing chain in September ... had to replace the water pump and was already there ... so I did them both. I had about 12 degrees of slop which equals 6 degrees of crank rotation (it was about ready to jump a tooth). A cold chisel placed at the teeth where the keyway is and a couple of blows will crack the crank gear and it will slip right off. All in all a pretty easy job once you get to it .

Plastic gears????? I duno bout that.

 

[UB2 SLOW]

I am no expert, but if you are going to be pulling the Water pump off and you engine has close to 100K on it, I would go ahead and do it. I changed my out at 80K, because I had the engine apart anyway and it looked like it was getting loose.

 

[Alloydude]

Yep, Plastic. The cam gear was made out of aluminum and the teeth on the gear where plastic. GM used this set up to quiet the noise made by the timing chain. I had a 71 Nova and when I put the timing light on it the mark on the balancer would move erratically. The cause was that several of the plastic teeth on the cam gear had broken off

 

[rrubel]

They're actually nylon, in case you're thinking "Plastic??!? How can that hold up to any stress??". Many companys do this, for the reason that Alloydude mentioned. Didn't think the Vette had them, though. GM used to have metal teeth that were just nylon coated; guess no longer.

You can rent/buy a gear puller specifically for GM timing chains (there's a couple bolt holes in the crank gear). I'd be leery of hitting the crank for fear of damaging the bearings.

Also, if anyone wants, free of charge, a low-mileage early C4 timing chain and gears (the non-step-nose cam style, 86 and before, all metal parts) let me know. Just cover shipping costs. It's got roughly 8k miles on it, but I'm installing a newer cam and needed a newer gear style (the holes are different).
[RICHR]

 

[Hrtbeat1]

I was actually kinda leery about hitting the crank also. I've done it a couple of times now (different cars) with no ill effects. If you place the cold chisel right at the keyway it won't take many whacks. You can't really get much force due to the angle ect. I think mine split in five blows. Once it cracks it will just slip off.


My new timing gears are all metal. Cloyes true roller. No nylon or plastic. I can't tell that there is any noticeable noise from the chain. The one that came off was all metal also. It makes sense that they would coat them with nylon to reduce the noise. I've just never see one like that.

C ya

 

[Skant]

My inclination would be to leave it alone unless it had some problem that warrants doing surgery on it. When timing chains get worn out, they become loose, and it makes the engine become increasingly sloppy and erratic.

I don't believe the vette is an interference engine, so you don't have to worry about self destructing the valve train if the chain just plain gave up suddenly... which shouldn't happen without some prior symptoms. (In case you don't know... some engines have no clearance between opens valves and the pistons... so if the valve train fails, the pistons will collide with the valves and cause massive damage to the engine. I think that type of arrangement would be strange on a V8 though.. I think it's common in small displacement performance motors).

If it ain't broke, don't fix it.

If you're working in that area for other reasons, go ahead and replace it while it's convenient. But otherwise, you probably aught to try to get as many miles out of it as you can.

- Skant

 

[MBDiagMan]

Skant is right on the money. If it ain't broke, don't fix it.

Your '88 has a roller camshaft which decreases the load and strain on the timing gears and chain to near nothing. Additionally these engines, unlike many newer overhead cam engines with belts, do not BREAK the timing chain. When they get worn they will jump a tooth. The engine will not be destroyed. When this happens you will simply go through the same parts and labor then as you would now if you changed it for the heck of it.

Drive it, enjoy it, do good preventive maintenance, fix it when it breaks, but forget about the timing chain in this particular engine.

Good luck,
Doc

 

[Bonnell]

That is good news! I do not like doing things like that without a reason. I remember long ago hearing that a broken timimg chain can ruin the engine. I'm relieved that it won't.

Thanks.

 

[MBDiagMan]

Let me be clear. There ARE MANY cars in which belt or chain problems will indeed hand grenade the engine. Yours is not one of them.

Have a great day,

 

[oldace84]

Guess I'm just lazy. I bought the Cloydes True double roller timing chain, a chrome cover, and a Fluid Dampener. Gave it all to my mechanic's garage and let him do it.

Also had him change my cat, with a Random Tech HP Cat.
Good Luck
tony

 

[Alloydude]

Yeah. I installed a nice shiny chrome timing cover on mine also only nobody can see it with all the other stuff on the front of the motor :cry But I know its there lol

 

[MBDiagMan]

An '84 is a different proposition when it comes to the timing set. This is a flat tappet cam rather than a roller cam as was the car that the original poster asked the question about. A flat tappet cam puts MUCH more load on the timing set.

Have a great day,