I finally got my most recent purchase up on the "big jackstand" and checked out the structural bits. There is some damage. Like it ran over a median or 10 ton bouder, but I can fix that.

The damage to the underside included tweaking the engine tins (both horizontal and vertical) about an inch up and an inch left on the driver's side. So the engine may have / must have taken a hit too.

My biggest concern is the "clacking" sound the engine makes. I started it up just fine. It idled fine for the 20 seconds I was willing to let it run with all that racket going on. Then I shut it off and started running through the possibilities. Needless to say, most of them are not good. Gerbil with a jackhammer was the first one to come to mind. Just kidding.

My question is, where should I start to try to find the source of this sound?

Thanks, Dawn

Valves

Crap in the engine impeller

Off the top of my head I am thinking possibly a valve adjustment. But rest assured, we have some serious experts on here and they will likely chime in.

Agree with the above but could also be cylinder head loose which will cause the valves and push rods to be noisy.

Tap Dancers in the heads

Dawn - With the engine turned off, stick your hand down between the firewall and engine and see if something fell into the fan. I know the noise was not there when we drove the car onto the uhaul from the prior owner but I remember hearing a rattle when I started it at home. Something loose could have fallen into that area during the trip. Mark

No worries, Mark.
I wasn't sure how much clearance there was in that area to allow a hand to reach. I personally thought something in the fan could be the case, but was advised by the Chevy guys in the garage that the sound was "inside" the engine. I do think I will explore the fan area first. To me it sounded like it was echoing. So I wasn't sure if it was the engine bay acoustics or something tapping on metal.

If anyone wants to chime in... just for future reference, Do I need to drop the engine to properly inspect/adjust the valves?

Thanks again, Dawn

No need to drop the engine on a /4 ... middle valves are a little tight but can be done using a dime as a screwdriver .. being a contortionist is a plus.

Now on a six ... well ...

It probably sounds nothing like this, but what about an exhaust leak? The rock would have bent the headers causing a leak, and the valves are so close to the exhaust you would hear the valvetrain quite loudly. It probably wouldn't sound like it was "inside" the engine though....

First, and no offense to the chevy guys (I drive and repair chevy's too), but the sounds in a type 4 engine bay are nothing like that of a chevy. Check the fan like the others have said. If this is an unknown car, pull the covers and check the valves for one that is very loose. Since the engine sustained a hit, I would also check the heat exchanger and all its parts for tightness and fit, and the headers themselves for proper torque. A small leak there can sound like a very big clack. You didn't say how loud the clack is. That could be another clue. If you just can't find it, put it on jackstands and crawl under it with the engine running. Use a length of rubber tubing as a stethoscope to narrow it down.

Can't resist the thread title:
"Everyone look what's going down."

I thought of exhaust leak too. It can be deceiving how it might sound like something clacking. Also, if the connection to the air injection port comes loose you will get a sound like that (if this is a late model car that has it). Probably not the cause in this case, but always good to get all the possibilities out there.

Okay, so on the way home, I'm stopping by the garage. I have my list of suggestions. Let me spell them out here and correct me if I'm proceeding in a logical manner.
1 - Check for debris in the impeller fan
2 - Check each exhaust connection for gaskets & fit
3 - Check headers for holes
4 - Check for loose cylinder head - Would love some "how to" on this one
5 - Remove valve covers and check for loose valves
6 - Not sure what the air injection port is just yet, but I'll find it
7 - Change the oil and filter (nobody mentioned this, but it's a little low and dark)
By the way, what brand and weight oil is recommended?

Last but not least... If I do have a loose valve or cylinder head, will it hurt the engine (any more than it already could be) if i let it run for 5 or 10 minutes while I crawl around underneath and listen for the source?

I love this shtuff!
Dawn

Loose cylinder head: With valve covers off you can torque the nuts on the studs. Check them when adjusting valves

Well you only check two of them unless you remove the rocker stands. Then you can only get 4. the other 4 are under the top engine tin.


If this is the 75, Then you probably do have the air injection ports. They are screwed into the head beside where the intake runners are bolted to the head. If they are loose it will make a hell of a noise.

Before you strip too many parts off, take a good look at the push rod tubes too. If it's idling fine, the valves may be working OK, just a lot of racket from the pushrods banging on the inside of the tubes... Even with a bent pushrod, the valves may open enough to keep the engine running, but they would be slamming shut due to the bent rods.


Good luck

The crankshaft probably broke in half from the impact ...

...does it sound like "...a thousand people in the street..."

Had to

And the winner is...


Push rods banging on the inside of the tubes. I checked everyting but the crankshaft (sorry Sir Andy, I couldn't bring myself to drop the engine yet )

It turns out, the oil level was a little low and a little thin. Don't know what weight it started out as, but by all estimates it was at least 1/2 gasoline.

An oil change and a few minutes of running totally eliminated the clacking.

So now I have a new question... What would force that much fuel into the oil?
Possibly the lack of a fuel pressure regulator?

Thanks again!!!
Dawn

If it has carbs it could be stuck floats. If FI, bad injectors. Something is causing fuel to run down past the piston rings into the oil. I use Mobil 1 10w50. I would determine the cause of gas in the oil before doing much else.