[67GTO1883]

My 67 GTO has a stock 400 with 4 speed and has recently developed an engine knocking or tapping sound coming fron drivers side rear of engine. I already readjusted rocker arms, noise didn't change or get any better. Tapping changes with RPM's but doesn't get louder, only faster. Im thinking lifter or bearing going bad but can't determine exact location. Any ideas or how to diagnose?

[richardk]

Exhaust leak? Get a length of hose, hold one end next to your ear and move the other end around in the area of the noise. This should help pinpoint the source of the noise.

[Garage Goat]

A wooden broom handle works good too.

[merlotgoat]

Could be a rod bearing. One at a time, pull a plug wire on each cylinder and listen to the noise. If it goes away when you pull off the wire, then most likely a rod bearing knocking on that particular cylinder.

[hottrodd]

I know it sounds crazy, but check flywheel/ clutch bolts, if one or all loosen , u cxn get a knocking sound likes rod knocking

[fatguyterry]

i have a 67 400 also, mine did the same thing. and I did the same as you and it was still there. I would do a compression test, my was two valves starting to stick in the guides, just a little. causing the tap, until I bent two valves.

[zephyrracer]

Sound travels so the broom handle works great, check the fuel pump for noise.
Good luck Gregg

[JTT99]

I know this sounds to simple but I learned many years ago in high school with my first 389 the lifters will tap if the oil level is a little low.

[HaloMedic]

Before you start this engine I would drain the oil and look for brass flecks I know it would have you better results to get it warm first also take off oil filter and cut it open look for metal . cheap insurance to change the oil and see then use a broomstick and damage the engine more not that the stick idea is bad. just running the engine at this point could cause more damage

I burnt a bearing not to long ago but I knew right off that it was a bearing, it was burnt not scored so I had no metal in the oil

[1966geeto]

HF sells a cheap auto stethoscope works well I have used a long extension as metallic noise travels well up metal as Merlo suggested start puling plug wires in the area of noise if it changes then you have some lower end issues and shut down the eng drain oil and check if not pull valve cover see if you have a collapsed lifter exhaust noise is more of a tick than a knock loose flex plate or cracked flex plate will also cause a knock.

[Skidmark]

Originally Posted by 1966geeto

HF sells a cheap auto stethoscope works well I have used a long extension as metallic noise travels well up metal as Merlo suggested start puling plug wires in the area of noise if it changes then you have some lower end issues and shut down the eng drain oil and check if not pull valve cover see if you have a collapsed lifter exhaust noise is more of a tick than a knock loose flex plate or cracked flex plate will also cause a knock.

Ok here goes, waking up an old thread. What does a collapsed lifter look like. I'm guessing it is shorter than the others when engine running. Also if one lifter is tapping only after engine is warm but not when engine is cold, can that lifter be collapsed. Thanks