So, I just started my 2.8 rebuild tonight... poped the timing cover and wouldn't u know! The timing chain has a ton of slack! My question is how much slack us too much and how does a chain expand anyways?

Sorry I can't tell you exactly how much slack is allowable. They get loose because of two reasons, the first is that they will stretch over time simply from the force that's exerted on them. The second reason is that the pins that the teeth on the gears mate up with will wear down out of round. The wear on each pin is almost insignificant but when you add up the wear on all of the pins together, you get some slack.

On a new installation, there isn't much more than 3/16" deflection when you push on one side of the chain. Don't forget to have a good look at the chain guide too. They're inexpensive... around $15 here in Canada. Here's how tight a brand new chain and sprocket set looks:

The left side of the chain will have some slack, the right side should be more taut.

Of internal parts that break, the timing chain is #1. If your timing chain has more than 20,000 miles on it and you have the engine open, you should replace it.

quote Originally posted by phonedawgz: Of internal parts that break, the timing chain is #1. If your timing chain has more than 20,000 miles on it and you have the engine open, you should replace it.

20,000 miles is a bit low to be changing a chain on a stock or mostly stock motor don't you think?

I would think so too... this is a chain, not a belt. 80,000 miles is where I would replace it preventatively if it were apart for another reason. Otherwise, a chain can easily last 150,000 miles without worry. Many people run them for a lot longer than that.

It is a chain not a belt, but I am not inside my engine that often. I figure if I'm at that point, the cost of a chain is inexpensive compared to the time cost of me removing the engine.

Most likely you are extending the life of your engine by the number of mile on the chain, for the cost of your chain.

took mine apart at about 10K, No slack whatsoeer ! (double row)

Thanks guys... I'm gonna take ur advice and replace it! The teeth are fine!.... the chain itself...honestly I don't knoe how it survived to begin with!! I don't know why they even bother with chains and belts! What's wrong with a gear system

I think Edelbrock makes a gear system that fits the 2.8, but GM (and everyone else) uses chains because they are cheap and they still last a long time.

quote Originally posted by fieromatty: I don't know why they even bother with chains and belts! What's wrong with a gear system

Ask anybody that owns a duke. And if gears are so great, why did dukes change to chains in the 92-93 engines.
Actually, you only have to look at how much contact is bearing the force in a gear system (only a couple of teeth), compared to how much in a chain system (nearly 180 degrees on the small gear, and over 180 degrees on the big gear).

Metal Gears are great ! fiber not so good. Even the old Flat Heads used angle cut gear drives, lasted forever ! Don't replace "JUST" the chain !

quote Originally posted by Lou6t4gto: Metal Gears are great ! fiber not so good. Even the old Flat Heads used angle cut gear drives, lasted forever ! Don't replace "JUST" the chain !

What do you mean "just"

Why replace gears... they look great!

quote Originally posted by Lou6t4gto: Metal Gears are great ! fiber not so good.

True. GM used fiber gears on the Duke because they are quiet, but they wear/strip.
Metal gears ARE available for the Duke but you get the "supercharged" gear whine

That's why GM went to chains, last longer than fiber gears and still quiet.

If you have your 2.8 engine apart, change the chain.

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"JUST" ....There IS a "reason" they sell a chain & gears "as a set". you may not be able to "SEE" it, but the new chain & old gears ARE a little different from wear patterns. (you don't want to end up "wondering" why did my new chain go to hell in a month & have to try it again) we're talking under $50 here, Not a pace to cut corners.

I heard that these chains can start to stretch after only 10k miles too... but only to a certain point before the chain guides eventually wear (or break).

But yeah, they don't NEED to be replaced... I've seen chain driven motors go for hundreds of thousands of miles.

Even modern belt cars CAN go 100k without needing a belt changed, although... I wouldn't go 60k miles without changning a belt.

But... take a look at the Crown Victoria... the old police cars see heavy use, and the mileage isn't even the whole story since they sit for hours with the cars running idle.

They go up for auction, and then get sold to cab companies who put another 200k miles on them.

It's not abnormal to see a Crown Victoria in the junkyard with over 300k miles on it... and about the only thing still good on it... is the timing chain.

But, like he said... if you've got the engine out, why not? At 20k miles, at the very least you'll be able to get optimal performance from the motor.


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Todd,
2008 Jeep Patriot Limited 4x2
2002 Ford Explorer Sport 2dr 4x2
2002 Ford Crown Victoria LX
1987 Pontiac Fiero SE / V6
1973 Volkswagen Type-2 Transporter

[This message has been edited by 82-T/A [At Work] (edited 10-05-2010).]