Used SHO...Unfamiliar Sound

[delasouza]

Just bought a used '90 SHO with 130,000 miles. She is in beautiful shape and runs good. Owner had receipts for the 60k kit installed at 120k and all the maintenance that he perfomed on it.
BUT... today I heard a slight "knocking" sound when the engine was idling. I put my ear on one of the intake runners and it was distinct. I really can't tell because it sounds just like a problem I had with a '95 Toyota Camry. It sounded like a rod knock but actually it was a broken crank pulley. I only paid $1300 for the SHO so I can't expect the world. Anyone have any ideas??? These engines have a reliable reputation so I'm holding my breath. I'll take any advice on what to listen for.

 

[Mr Anonymous]

If it's coming from the top of the engine It could be valve/cam chatter or a failing timing chain tensioner. If you do a search under 'stethoscope', there are some good suggestions as to how to pinpoint engine noises as well as some suggestions on different items that can be used in place of the $15 mechanics stethoscope sold at most auto parts stores.

 

[sdpatt]

For a distinct "knock," the two primary possibilities are worn connecting rod bearings or the crankshaft damper rocking on a worn crankshaft Woodruff key. Check the crankshaft damper to see if it is loose and can be rotated with play on the keyway. If you find there is play, search the Forum for "crank cancer." Also, check the 19mm damper bolt for torque (113-126 lb-ft).

If a loose damper is not the source, it may be a worn connecting rod bearing. After replacing the bearings on my engine at 269,000 miles, I found them worn, but not damaged. See the topic here. The bearings are only $45 from NAPA auto parts, but the labor is a bit more pricey. After completing the bearing replacement, I consider it much more simple than a 60K service and wonder why I waited so long to do it.