I have a 93 Jimmy 4.3 with an tick that won't seem to go away. It cannot hear it at high or low idle (even if it is accelerated with the brake on) but it is obvious under load or accelerating. It is louder when cold and quiets down dramatically when it warms to operating temp. It has 172,000 miles on it and runs very well. The only issue before the noise is that it blows smoke at every startup. Burns very little oil. I have intended to replace the seals but haven't gotten to it yet.

The ticking start about 6 weeks ago. I thought it might be the usual sticky lifter issue so I tried some additives. Eventually I ran Seafoam through the system. Then some MMM. Didn't resolve it.

I used a stethoscope and thought I heard clicking under the passenger side rocker cover. I removed the cover, rocker arms, and pushrods. Found one pushrod bent so I replaced it. Put it back together and it rain quiet.....for a day. So it is either something else causing the tick or I bent the pushrod again.

I waited til it got louder but could not hear it under the valve covers or anywhere else. Pulled both covers this time, checked the torque on the rockers, checked all the parts.... no obvious problems. Used a "check" I read about for lifters (pushing the pushrod into the lifter feeling for sponginess.... all solid). The new pushrod from last time is fine.

This is the first time I have had both covers off and I took some pics. The passenger side is much darker that the driver's side. Not that obvious on the pics but it I has the same kind of difference you would see under the intake when the FPR has leaked but the nut kit side is OK.

Any help on where to go to find and fix the tick? Also, any ideas on what would cause one side of the engine to so much darker/lighter than the other side?

The pics:
First pic is the passenger side
Second pic is of the rockers and pushrods; three left rockers and pushrods are the passenger side. Rest are from the driver's (cleaner) side
Last pic is the driver's side

 

It definitely sounds like you have a problem with either a lifter or a bent push rod. I do not know what would cause a push rod to bend in a few days other than a defect or high RPM stint... A stuck lifter is a likely source of the problem.

You would want to replace all of the lifters and inspect all of the push rods if you were to dig into it. The work is basically the same to replace one as it is to replace all 12.

 

Thanks for the info. All the pushrods look good (straight) now. After I change the valve stem seals I will probably dig deeper and check the lifters. Since I work outside it will depend on the weather.