Gawdawful engine knock...

I was puttering down the road at around 55 - 60 MPH over the weekend and suddenly without warning it developed the gawdawfullest grinding, clanking, knocking sound with badassed vibrations. I limped home @ 1000 RPM. I have oil pressure about 15 PSI @ 1000 RPM. It sounds almost like a broken rod, but usually you would get a little warning like a rod knock before the rod busted. The engine is a ZZ-3 Chev crate motor with pink rods with only about 10,000 miles or less on it. The harmonic balancer looks OK and I haven't pulled the inspection cover yet to see if the torque converter self-destructed.

Any ideas??

It sounds like the engine might have a major failure. But before digging in there, check to see if the flywheel is cracked or loose. This is more common with an automatic. Very noisy.

Ken Styer

Would it be worth doing an oil analysis before tearing into a fresh motor?
Even do it the redneck way, take off the filter and cut it open and look for chunks

My sudden gawdawful knock was a broken rocker stud. Happened at an idle. Easy fix and no damage.

Whew! Glad it turned out minor!

I dug into it a little more this AM, jacked it up, pulled the flywheel inspection plate and watched the flywheel and converter turn while the war department cranked it (ign. unplugged). No noise when cranking, flywheel turns straight, no dents in the pan and it gets oil pressure up to over 10 PSI after one engine rev while cranking. The busted rocker stud is a very real possibility, but I can't imagine a little rocker arm and pushrod making all that racket and big vibration, but I can imagine the noise a pushrod makes slamming back and forth against the valve cover and it sounds a whole lot like that. It has a roller cam, so it really accelerates the pushrods and it makes sense that it would not make noises on cranking with a busted stud. Will pull the valve covers tonight and let you know.

Thanks for the hints.....

Dave

PS:

It did spit back thru the carb a couple of times earlier in the day, so the busted stud is sounding more and more real.

So much for the busted stud, wishful thinking on my part. Pulled the valve covers yesterday, valve train is healthy. I wonder if there is such a thing as a partially busted timing chain???? I am going to pull the engine this week, might as well since I am putting a 700R4 behind it.

Will post the findings.....

timing chain may have jumped a tooth. that would cause the engine to misfire back thru the carb.

I have about convinced myself that with the huge vibrations it developed that the torque converter has blown up internally, but is still pulling. Logic is that something as light as a timing chain or con rod would not cause such a ruckus. I'll loosen the converter from the flywheel, light it up and see if it goes away.

Will keep you posted.

Dave