Ok here's the cliff notes version.....I bought an 86 Z28 that supposedly had a locked and or blown motor for $700. Car is in pretty good condition with one owner who gave it to her son who did the damage so I said WTH and bought it. First matter of order, check all the fluids. All good minus the motor. Almost not a drop of oil. Expected. Put a few quarts in, bought a battery, hooked it up, put gas in it and simply turned the switch and bumped it over several times but didn't try to start it. I then checked all vaccum hoses, and tried to crank it. It spun over twice then locked and wouldn't do a thing else... Objective one completed. Motor not locked so I had a starting base. I believed the starter was toast and bless the kids heart I don't even think they ever changed spark plugs in the LG4. Installed the new starter this morning, hooked the battery back up, turned the switch a several poofs of smoke later the damn thing is alive again. Run great? Not by any means but running non the less. On the passenger side after idling and belts squawking all over the place I'm hearing a hell of a knock. I'm thinking a knocking rod. I have another motor I will build for it but with that being said I still wouldn't mind the minor accomplishment of getting this motor running enough to merely move around in my driveway while I start suspenion work, drivetrain work etc.

Now.....the something else comment came into effect for I cut the motor off after letting it run for several mins, then cranked it again and put the car in gear...what happen? Well the damn knocking stopped....COMPLETELY! So my question to the Guru's is..."What the hell is it?" Bent pushrods? Loose Rocker Arm? Stuck valve or combo of one as well as a knocking rod? I know the kid raced the car but he also didn't know about the car other than how to put gas in it. Before I started tearing it apart to get an answer I wanted to see if the Guru's here had an idea. Thanks in advance.

 

I don't know about any "gurus", but...

Cracked flex plate (around the bolts at the crank flange)

 

Either the cracked flex plate mentioned, or check the torque convertor bolts. Maybe the kid vibrated em a bit loose beating on the car. I've seen it happen once on a friend's 80 Z28. Dam thing sounded like the rod bearings fell out, lol Lo and behold the tq convertor was loose

 

Cool, I will add that to the list. I actually recorded a video but not sure how to upload it here from my phone.