My '87 Dodge Ram shortbed has been running a bit low on power lately.

I hooked up my timing light and it's generally on the mark but it's varying frmo one strobe to the next, sometimes looks like by a few degrees.

In other words, the mark is not staying totally still.

Is this normal and if not what might be causing it?

Thanks.

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'87 D150 Slant-6 A904 with wooden cap

tired timing chain

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Your timing chain has slack if the mark keeps moving back and forth at a set rpm....

Best way to confirm and check is to pull the distributor cap and pull the spark plugs and roll the crank forward by hand a bit then backwards the same amount and look at the distributor rotor while doing it or have a friend look while you roll the crank....the rotor should immediately move in the direction that the crank is being rolled, if there is any delay (especially when you change directions from forward to backwards) then the timing chain is a little loose and needs to be replaced and the cam set by degreeing not by the "dots" on the gears.

Thanks, that makes a ton of sense.

It seems more steady at higher RPMs when i rev it up, and i see the advance as well.

But still not 100% steady.

How big a deal is replcing the timing chain?

thanks.

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'87 D150 Slant-6 A904 with wooden cap

Yes, i did this and it seems to have a lot of play, the rotor is not very "tight" to the crankshaft.

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'87 D150 Slant-6 A904 with wooden cap

My 83 D150 had the same issue with an unsteady timing mark when checked with a timing light, swapped out the lean burn ignition for an HEI and the timing mark is rock steady.

...you will still need to do the chain,,,,

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Yeah....Im the one who destroyed this rare, vintage automobile.....