472 strange knocking

RoadRatX · #1 (**permalink**) 02-22-07, 06:15 PM

Recently while driving down the highway the radiator hose blew in my '69 Fleetwood. I had it replaced and noticed a new knocking/clacking sound coming from the engine. One of the mechanics was passing by and said it sounded like a lifter or valve adjuster that was slapping hard. So I let it idle a while and the noise went away and I drove home the remaining 80miles.

Now when I let it idle in park I hear the knocking, but it's sporadic. Sometimes it's there and other times it's not. Or it's there than goes away after about 10minutes. Dropping into drive it becomes less noticeable, but you can still hear it...accelerating makes it more noticeable and around 40-45mph you can really hear it.

The oil was low at the time of radiator hose blowing, since then I've brought that up to the proper level and tossed in some MMO for good measure. The noise is still there, albeit not as loud on idle. Someone mentioned that it sounded like it got hot with low oil (which it did) and that the fix could be as easy as a couple new rockers and push rods. Also a friend with a '68 suggested that there might not be enough oil getting to the lifter....could there be a deposit clogging things up?

If anyone can help it'd be greatly appreciated.

LAC-MAN · #2 (**permalink**) 02-22-07, 09:07 PM

When Was The Last Time You Had The Engine Flushed? If An Oil Passage Is Clogged That Would Cause Oil Starvation To Some Of Your Lifters. Try A Good Engine Cleaning.

RoadRatX · #3 (**permalink**) 02-22-07, 09:11 PM

Not sure when it was last flushed. It's a recent purchase from about two weeks ago now. The block was completely rebuilt not long ago as it hasn't even gotten the proper break-in miles on her yet.

534BC · #4 (**permalink**) 02-23-07, 03:59 PM

sounds like a piston/pin knock that comes and goes.

dkozloski · #5 (**permalink**) 02-23-07, 05:08 PM

You might have scuffed a piston with a little metal transfer.

RoadRatX · #6 (**permalink**) 02-23-07, 05:23 PM

Quote:

Originally Posted by 534BC

sounds like a piston/pin knock that comes and goes.

Could be, but why woul it not be there on idle in park most of the time and then go away when dropped into drive? Not to mention be there consistently when accelerating? I pretend not to know such things...just a curious question...

Quote:

Originally Posted by dkozloski

You might have scuffed a piston with a little metal transfer.

Hmmm...it's possible. Not quite sure how that would've happened though...

534BC · #7 (**permalink**) 02-24-07, 03:47 PM

Your saying it goes away after 10 minutes indicated something temp related to dissimilar metals. My first thought is an aluminum piston in an iron block or a steel pin in an aluminum piston.

The load change on the engine can make knocks go away, most of them anyways.

RoadRatX · #8 (**permalink**) 02-24-07, 04:21 PM

Quote:

Originally Posted by 534BC

Your saying it goes away after 10 minutes indicated something temp related to dissimilar metals. My first thought is an aluminum piston in an iron block or a steel pin in an aluminum piston.

The load change on the engine can make knocks go away, most of them anyways.

It's possible...it was recently rebuilt. I would assume they would've kept things inline in that dept. However, would it be coming back as soon as acceleration is applied?

534BC · #9 (**permalink**) 02-25-07, 10:02 AM

I'm not at all saying there is anything wrong with using the parts in the engine or saying anything thing about the rebuild (I didn't know)

I would say that the knocking has to do with the engine being low on oil and water. Regardless of what caused the knock or what the knock is when the load/temp/rpm/acceleration rate is changed the noise can come and go.

Maybe I'm not clear here on the goal? Check me out.

Find knock, fix knock, find cause, try not to repeat. An engine shop can listen to it and guess it with nearly 100% accuracy, especially if given the oil/water info.

RoadRatX · #10 (**permalink**) 02-25-07, 06:38 PM

Well, 534BC, I've spent the past week trying to figure out what the problem is. There could be something going on with oil lines or the such...or just a loose spring or rocker. Hard to say. Either way it's gonna go over to a shop either Tues or Weds for them to look it over and let me know.

Thanks everyone for their help!

RoadRatX · #11 (**permalink**) 03-01-07, 06:43 AM

Well here's a little update on the situation here....

Had a mechanic come over to give her a listen after hours. It's definitely a starvation issue with the oil. Could be a few things at this point, but until I take the valve covers off and see what's going on for sure I won't know for sure. He believes that if both casings are dry and springs are squishy that it's probably the cam bearing that slid out of place a bit and the oil hole is been blocked due to that.

RoadRatX · #12 (**permalink**) 04-03-07, 10:43 PM

Well things continue to get stranger and stranger. The shop I ended up taking her to was definitely run by hacks looking for a quick buck rather than fixing things. They said that after a quick overview the entire engine had to be replaced because the knock "sounded like it was coming from in the engine". I'd have to agree...why else would I have brought it there?! (one other place went as far as saying they'd need money upfront! )

The few other excuses they gave was that the compression was lower than it should be and there was lots of surface rust. (I still don't know what the surface rust has to do with the engine, but ok...) Now call me crazy, but aren't there several reasons for an engine losing compression? From what I know that's not a reason to "condemn the engine" after only looking at it for about 20minutes.

Also, the tapping is definitely coming from the top of the engine. There is an odd sound to the engine deeper within. Could that be from the compression being off?

Yesterday when I was running the engine in the parking lot at my place it sounded like it was sucking a lot of air in the vicinity of the carborator. Almost like a jet intake...the carb that's on there now isn't the original as Rochester Carb couldn't be located. So a Holley 4 barrel is up there in it's stead. Could this be having an impact at all or is just a carb issue?

Either way I'm taking it to another shop for a 2nd opinion today or tomorrow. The guy I bought the car from did say that they bought the engine from a company (is looking up the info) and he didn't even get a chance to adjust the valves...could this be the cause of my headache? I guess we'll find out here in a few days hopefully.

cadillac_al · #13 (**permalink**) 04-06-07, 03:07 PM

I would take the valve covers off and see if the rocker arms look normal and have oil on them. Go ahead and start it for a minute and see if you can hear the knocking coming from a rocker arm. It may start squirting some oil so be ready to turn it off or look it over real quick. I don't think those valves are adjustable anyway but I'm not positive on that. You said it goes away after a few minutes or when it warms up. Is it knocking when it is warm too? I have never had any luck with used Hollys but if yours is running ok, I guess I would leave it alone.

The Ape Man · #14 (**permalink**) 04-06-07, 03:24 PM

Whackiest knock I ever heard from one of these was due to the crankshaft oil slinger. The crank flange was not pressed all the way on during a rebuild and the slinger made a knocking noise sometimes. It sounded like a main bearing knock. Sometimes it would seem to change when dropping the car in drive. The engine ran like that for about 75,000 miles until I pulled it apart. If you do have a real rod knock, things will get worse rapidly. A main knock in these engines can sometimes just be more than an annoyance.

Koooop · #15 (**permalink**) 04-09-07, 01:59 AM

I had a TH400 with a knock like the one you described, I think it was a bad torque converter? Hell if I remember.