So I just got my 72 Polara after the engine has been rebuilt. Took it for a ride and drove nicely. I had to drive the car back down from San Francisco to Los Angeles the same day, long story.

Anyway, on the freeway, the engine start to make noises every time the gas is pedal is pushed, it sounded exactly like thousands of tiny gravels hitting the body, or high-pitched glass being crushed or scraping.

Then further down the road and up hills, the engine got some pops and hesitations, my girlfriend driving behind me noticed clouds of smoke coming from the exhaust at each pop.

Lastly, after 7 hours of driving, at stops and red lights you can clearly hear a nasty rattling coming from inside the engine. (Park, Drive, Neutral, same). You can listen here

On a side note, if this is relevant: I was driving most of the time between 65 to 80MPH.
The car is hard to start cold or hot, someone mentioned about loose battery terminals, but I doubt this is related to all these noises.
Did not broke down and the Polara drove all the way.

 

Couple of thoughts: The gravely noise sounds like pinging/detonation. Not sure on the compression, but if it is higher than 10, it will be more prone to it. Adjust the timing and put higher octane gas in. As for the other noises, here are some suggestions. Check spark plugs, make sure none came out or loose. Check your exhaust, make sure you have no exhaust leaks. then finally, check your valves. Each one should be torqued to I believe 25. My assumption is this is a standard rebuild, if so these would be a good start. You never mentioned oil pressure, again my assumption is it is above 25 and/or no idiot light. Does it build pressure with RPM's (approx 10 for every thousand). Also, what was the engine temp, if it was normal (Based on thermostat), sounds like typical engine break in items. Post more, let us know

 

The "gravel" sounds like serious detonation. You can seriously damage an engine with prolonged "pinging" and break rings and piston lands.

Your audio file is hard to say, I agree that sounds more like exhaust leak noise, but difficult to say from that. Get a length of fuel hose, hold to your ear, and probe around the exhaust.

Stick the hose into the breather / oil filler and see if it sounds like valve train noise

I hope you didn't cause damage. The engine may be out of time (too much advance), or overheating, or just not high enough octane fuel. Without knowing the compression ratio and cam specifics, hard to say.

You definately need to find a good local mechanic to help you with this.

 

Cazbah362: Thank you I will check these. Oil pressure is fine, no light on the dash and no overheating either.

440roadrunner: Well the prolonged pinging lasted 7 hours at 75 MPH and now I have this noise rattling inside the engine body that I haven't heard before the trip. I think I damaged the engine...
It does sounds like an exhaust leak, as it is quite loud.

I forgot to mention: While driving and speeding up, the engine will pull the car forward, but a few seconds after it will start to hesitate and small shakes forward / backward that you can feel.
Also: the car shakes a lot and is very loud when idle or at a stop, without a steady purr, sounds like it's gonna choke on itself but then it revs itself up again, very intermittent.
Oil is not dirty.

 

I think you probably hurt the engine. I'd tear it down and inspect it before something really major goes wrong

 

Start with baseline tuning on the carb and timing. Check your vacuum. Read your plugs. Verify good ignition. Then do a cylinder leak-down test, and a compression test before you start tearing it apart. I know, trouble-shooting and testing is time-consuming, and not as fun as turning wrenches, but it IS cheaper! If you do these you should have your problem located before you even pop a valve cover.

 

Driving at those speeds will NOT hurt it.. something else is wrong.. Years Ago my grand Father HAD A 69 CRY 383 Drove it from LA, Ca to Lake Havasu, AZ averaged probably 90 mph most of the way, speed is not your problem. It sounds like someone did a terrible rebuild. Start by draining the oil into a VERY clean container, look for any thing shiny (bearing material) and do a compression test. From the other post, check the rocker arms for oil - They could have put the shafts in wrong limiting oil flow Like everyone has said You will probably have to take it apart..

 

Brought the car to a good classic car mechanic, sounds like something came out loose in the engine, they will take it apart and check it thoroughly, as I do not have the manpower to do all those things by myself.

Also, while bringing it to the shop, the oil light came on. I believe the oil pump might be at fault. The car got the engine rebuilt because of a blown timing chain back in July. However, not having much experience in this, they did not put a brand new oil pump, and they just cleaned and kept the old one. I thought this wouldn't be an issue since it seemed to work, but now I'm seriously questioning it. If it all comes down to a $40 part, I'm going to be pissed.

I will keep posted as this develops, but it sounds a bit more serious than I thought.
Plugs were okay and I get a decent / quick ignition.

Thank you all for your help!

 

Great, so it got fixed, the clutch plate was loose from the transmission (recorded noise came from), vacuum hose was older than a fossil and battery terminals were replaced along with thicker gauge cables, and timing was way off. Ignition is instant even on cold start. Took it for an hour drive on PCH and it rides great.
Thank you guys for your help!

 

PMiles - very nice to hear!