Should this timing chain be replaced? The timing chain is a KCM with "D6B" stamped into each link. The chain has about 12k miles on it and is about 12 years old.

[video:google]https://drive.google.com/open?id=0B47FH99TbpHuMkVDSm4yRTVHN2M&authuser=0[/video]

You can change it as long as you're in there, but it will run a long time like that. Many new chains develop a little slack very soon after install.

If I do replace it, what brand should I replace it with?

I believe as the chain stretches, the intake and exhaust valves open later and later in relation to the crankshaft. I believe that is called 'retarding' the camshaft, not 'advancing' the camshaft. I think retarding the camshaft will cause the engine to lose bottom-end power; correct?

It has to stretch a lot more than that to bother anything.

Small block mopars have one of the longest distances from crank to camshaft amount traditional V-8's.

They get sloppy faster than others.

You might set the dampener slit at 15 ATDC then with a 1&1/4" socket/breaker bar bump it back CCW carefully till the slit JUST centers on the TDC mark. have a helper watch the rotor and you bump the breaker bar back CW carefully till he hollers that the rotor JUST moved & that'll tell you how much timing change (spark scatter) you will be dealing with which is chain slop and dist tang slot slop combined and subtract the # of degrees of slop in the intergear/dist tang interface for the actual cam phasing change (yes, retarded). Twist the rotor lightly just not enough to get into the springs & measure the circumferential distance/play plus some math (c=PixD) to get the amt of intergear/dist tang slop. As said all chains stretch & a high dollar one (Rollmaster) will minimize that on a high dollar/racing app (as needed). EDIT on the intergear play multiply that by 2 to get the crank phasing number

My friend and I checked that via a dial guage on the piston top when the heads were off. When we moved the crank, the dial gauge indicated the piston moved. When we would turn the crank clockwise and then turn the crank very slowly counterclockwise, there was no delay indicated by the gauge, indicating to us the chain was not stretched.

Now I have the cover off and I see the chain has some play in it. So I am second guessing myself.

I will try your test, Robert, but I think I will find the chain is just fine. Thank you for the detailed write up.

As others have stated you're fine. Some of this (I posted) is just Nth degree/OCD craziness but its always a good idea to at least baseline where you are at then a person can make an informed decision

Cloyes 95387 Timing chain tensioner
https://www.rockauto.com/catalog/moreinfo.php?pk=1259253&cc=1361933&jnid=507&jpid=0

Rock auto $24.79

Look up under 2000 Ram 1500 3.9L V-6 -> Engine -> Timing chain tensioner.

Same part the other places are selling at twice the cost.

The timing mark floating around as you watch with a timing light at idle is where you SEE the slack in the chain best.

The mechanical test has been preformed and chain has past inspection. Agreed.

As many junk engines I have used, It would be a good idea to replace that chain now while the gaskets are open. I have changed cheaper ones with less slack and I have also had a dozen or more jumped t-chains in 35 yrs running junk by refusing to change it thinking it will last a little longer. roll them dice!

now that it is "USED" and has passed the spec test, what about another 10,000+ miles? is it going to start floating around then? are you going back in?

IMHO, $ well spent on a timing set now.



I like the pro-gear sets from Hughes and SUPERFORMANCE gaskets.

Of course the chain is stretched, the slack is taken up when the engine is running , but the cam timing has changed some in relationship to piston in the bore , but not enough that you would ever now it ...

Run it ...

Would you guys say timing gears are better than chains?

No. Gears transfer torsional harmonics from the crankshaft to the camshaft far more than a chain does. A belt drive is even better yet which is the reason they are used on serious race engines. You will be fine with a chain. If you are worried about it retarding the cam then degree the cam and put it where you want it.

Woa did I get that wrong!

We had a dial gauge on both the piston top AND a dial gauge on a camshaft lobe (see picture). When we moved the crankshaft clockwise, stopped, then slowly rotated the crankshaft counter clockwise, there was no delay in the gauge on the camshaft lobe providing a change in reading. That indicated to us the chain was in good shape.

[img]https://drive.google.com/open?id=0B47FH99TbpHubkZiQi1kOXdtS3M&authuser=0[/img]

Does your engine run in both directions ???

No, it does not run in both directions.

We were trying to see if there was play in the chain. Maybe that is not an accurate way to do it?

We *think* the cam was installed at 112 degree intake center-line. But I do not have the cam card and the engine builder does not remember where it was installed exactly (built the engine over 12 years ago).

The link provides the intake lobe measurements that we took with the gauges installed on the engine. [img:center]https://drive.google.com/open?id=0B47FH99TbpHueDhBRXNweFZrcmc&authuser=0[/img]

Exhaust lobe measurements:

[img:left]https://drive.google.com/open?id=0B47FH99TbpHucFVUdVd6NENiNTA&authuser=0[/img]