Engine ping after timing chain replacement

[vangremlin]

Good luck!

[LeesSummitEagle]

Here is another update. Rechecked timing today - its at 8* @ 1600rpm with no vacuum.  Got some Seafoam last night and poured about 1/3 can into carb while running then let it set for a while. When restarted, got some carbon out, but a lot of water. I don't know if is because of the Seafoam or something else has happened. Drove around the block and engine still pings on level ground. I have ordered some Amsoil to try next and well as new spark plugs.

[carnuck]

If the plugs don't clear up the ping then the chain was installed wrong.

[eaglebeek]

I'm leaning to the side of carnuck...it does seem something is amiss in the timing chain installation.

Harmonic balancers on 258s are built with a rubber cushion between the hub and the outer ring where the timing mark is. Even if the balancer appears OK the ring may have shifted on the hub a bit. That will throw the timing mark off and render a timing light useless.

There is a method by which the installation of the timing chain can be verified. It involves using a dial indicator on one of the #1 or #6 pushrods and measuring the lift as the crank rotates past top dead center. There are some other details, such as accounting for the hydraulic valve lifter, which I can't remember. And it's going to be tricky knowing exactly where top dead center is because of the well-used harmonic balancer.

Having said all of this, it's going to be easier to simply take the timing cover off and verify proper timing chain installation. It's not really difficult to do so, and the only part necessary to remove to gain access is the radiator.

It seems to me like this issue should be the responsibility of the shop that originally installed the timing chain.

[Amc1320]

I have found timing lights to be useless on 30 year old engines

Get a vacuum gauge , set timing and carb for best vacuum reading (prob around 19)

Take it for a drive, if it pings back off timing a tiny bit

repeat as needed

works every time

[carnuck]

I'd pull  #1 spark plug and set the timing mark to TDC. Then see if the balancer mark is off (use a plastic straw in the cylinder to find the top point of the piston travel by rolling the motor back and forth to find the center of where it doesn't move). If that is correct with the balancer then pull the valve cover and see if #1 or #6 rockers are at the crossover point (the opposite cylinder would be firing then). One of the rocker pairs will start to open if you roll the motor either way. The halfway point between where one closes and the other opens is the crossover. That is when the TDC mark should be lined up as well. If not, then the timing chain isn't set right.

[LeesSummitEagle]

Here is another update

When I took the car back to the shop that did the work, they verified that timing marks on balancer did line up with TDC. So this is what I have done so far:

Since I had a spare I replaced the EGR valve - still pings.

Reset timing for max manifold vacuum (23) and changed to proted vacuum - still pings.

Backed off to vacuum of 22 - still pings.

Installed NGK2288 plugs - still pings.

Had a spare igintion coil so I tried that - still pings.

Reset tining to 9^ at idle - did not hear any pining.

However I did notice a problem. While watching the timing mark with a light, at idle it was stable.
When I increased rpm at 2000 rpm the timing started to jump around. I had a spare cap and rotor and replaced but problem stayed. Disconected vacuum and the problem remains. I can see the mechnical advance kick in and timing is stable. Its only above 2000 rpm when I notice the problem. So, do I hav a distributor problem? I have a spare pickup assy to try.

Again thanks for all of the help!

[carnuck]

Timing advances as RPM goes up. That is perfectly normal due to the mechanical advance. The shop didn't line up the timing chain marks. Plain and simple. That or they were mis-marked. I have only seen that on 2.5L AMC 4 cyls (did it myself once. I was sooo ticked off!)

[IowaEagle]

I agree.  Timing marks on the gears were not correctly lined up.  Its easy to do if you are hurrying the job.  I think I spent more time on that part when I replaced my gears and chain.  If done right, timing does not have to be messed with.

[LeesSummitEagle]

Update:

Was almost ready to give up on this problem when I finally found the problem. It was something that I overlooked. The problem was caused by a partly restricted vacuum line to the distributor advance. I had vacuum, but it was weak and unstable. This was causing my timing to be all over the place. I assumed it was good because I replaced it about a year ago. After replacing the line and resetting timing, no more pinging and it is running like it did before. I believe that this has been my original problem before the timing chain & gears were replaced.

[eaglefreek]

Wow, glad you finally found it. It's amazing how something so small can cause an issue like that.