Again Engine knock

[steve from staten island]

I had someone listen to the knock in my engine and they agree there is something amiss. What i did notice is when the engine is cold three may be a knock but its barely noticeable,if at all. When the engine is warm then you can hear it. I pulled off the valve cover and saw nothing out of place. Could a wiped cam lobe give me this noise as the car is not posing through carb but could run better. Any thoughts and thanks

 

[RT K_line]

Loosen all the spark plug wires at the distributor after it's the worst then start the engine and pull one at a time to see if it's a single cylinder or not. If it doesn't change then probably not in the bottom end. Fresh engine? Good oil pressure? Cranks ok when hot?
If it had a wiped cam you would have seen the valve train loose somewhere.

 

[khryslerkid]

You have to think about the timing of the sound. Picture the moving parts. Valve components spin faster than the crank. At a faster rpm the sound changes with the rotation of the part. Try to think about the speed of the sound.

I had a guy ready to tear his engine out of his truck. He thought it was a rod knocking. I listened to it, useing a long shafted screwdriver against my ear and moved the tip to different areas on the engine, trying to home in on the sound. It wasn't fast enough of a sound for the valve train and it didn't sound right or deep enough for a rod. I just happened to touch the screwdriver on the fuel pump and bingo, that was making the sound.

Then he told me I was wrong. So I unbolted the fuel pump from the block and just let it lay there. Started the engine and the sound was gone. Saved him some serious time and money.

 

[Dibbons]

I had a ringing sound (almost like a distant bell) under the hood and could not figure it out. A shade tree type mechanic finally figured it out for me. One of the spacers the alternator bolt passes through was rattling. The spacer was just slightly too short for the bolt to snug it up nice and tight. That was a relief.

 

[WP29440SE]

just for shits pull off your accessory belts to rule out anything on the front. you'd be surprised how a bad water pump could sound

 

[steve from staten island]

You have to think about the timing of the sound. Picture the moving parts. Valve components spin faster than the crank. At a faster rpm the sound changes with the rotation of the part. Try to think about the speed of the sound.

I had a guy ready to tear his engine out of his truck. He thought it was a rod knocking. I listened to it, useing a long shafted screwdriver against my ear and moved the tip to different areas on the engine, trying to home in on the sound. It wasn't fast enough of a sound for the valve train and it didn't sound right or deep enough for a rod. I just happened to touch the screwdriver on the fuel pump and bingo, that was making the sound.

Then he told me I was wrong. So I unbolted the fuel pump from the block and just let it lay there. Started the engine and the sound was gone. Saved him some serious time and money.

When i bring the RPM up to say three grand its knocking very fast. You dont really hear it when its at say 1000 rpm as much. When you goose it you hear it very clearly

 

[1967coronet440]

Take some of the ideas above and rule everything else out before you tear it down.

 

[SublimeSixpack]

You called it a knock, but just to clarify is it a knock (as in a heavy and low in the block sound), or a tap (as in a light and higher up in the engine sound)?
Have you tried using a mechanics stethoscope to narrow down the area where the noise is the loudest?

 

[PP1RT]

Pull an oil sample and send it in. If you are losing bearing material it will show in the oil. Cheaper than tearing out the engine to look.

 

[burntorng70]

I had a knock that drove me crazy on an old slant six. It was the damper pulley bolts. The large center bolt loosened and the small ones rounded the holes. Also have had torque convertor bolts make noise. Forged pistons also will cause piston slap until they warm up, but it sounds like you have the opposite problem.

 

[72sunroof]

Very good ideas so far.

Another is get a mechanics stethoscope to listen to the block, by the water pump, the fuel pump, the torque converter and heads.
Pull the valve covers and start the engine, yes it will be messy, and hope it is there.
I had a knock and it was a cracked cylinder. I went through easiest to hardest.

 

[Daves69]

Don't forget to rule out the thrust bearing.

 

[PeteBell68]

I had someone listen to the knock in my engine and they agree there is something amiss. What i did notice is when the engine is cold three may be a knock but its barely noticeable,if at all. When the engine is warm then you can hear it. I pulled off the valve cover and saw nothing out of place. Could a wiped cam lobe give me this noise as the car is not posing through carb but could run better. Any thoughts and thanks

I had a cam lobe wipe about 2 years ago on a 350 chev that I abused for 10 years. It sounded like pots and pans rattling in the top end .It idled at 1000 rpm and when reved was harder to hear because of the engine sound and headers etc.
It didn't last long that way as just before it was rebuilt it could barely run .

 

[moper]

Some comments - the cam and valve train are slower than the crank, there's just more parts to them. Also valve train noises are much higher pitch because they are not buried in the block. You can user any long metal bar for a stethoscope as noted earlier. Screwdrivers, pry bars, an old strut rod, whatever. Put one end on a part, the other cup your hand around it and your ear and you'd be surprised at what you will hear whirring and clicking and stuff. Removing the accessory belts will eliminate a lot of sources. Also check the flex plate bolts and plate itself.

 

[steve from staten island]

Thanks. I bought a HF stethoscope and it sounds like maybe the top end. It is more noticeable when the engine is warmed up. I have the front of car jacked up and will be listening underneath tomorrow

 

[1967coronet440]

Keep us posted

 

[Ski 61701]

Sometimes when you listen underneath when the motor is running, they can have normal noises which if you arent familiar with you're gonna think the motor is going to blow up. Have you tried pulling one plug wire at a time to see if noises change?
Also, have you in essence put a load on the motor by quasi brake torquing it to see if you have a main brg prob? Just something to think about.

 

[R/T]

Same thing just happened to me, i hammered it tru a yellow light, a little high on the rev for an old cruiser, and then ten miles further, an awful sound like a loose pulley, luckily i was half a mile from home. Closer inspection sounded like the clutch coming apart, but it was fine. Top end ok too. I then suspected a cam bearing, so i did what no one wants to do and pulled the motor out and tore it down. It was # 2 rod bearing spinning itself silly. Good news is the block is standard unmolested 100,000 mile original, bad news is = 3k plu$ . At least now i'll have a brand new motor to take me into old age.

 

[lewtot184]

When i bring the RPM up to say three grand its knocking very fast. You dont really hear it when its at say 1000 rpm as much. When you goose it you hear it very clearly

valve train runs at half the speed of the crank. 1000rpm on the crank is 500rpm at the camshaft.

you might be surprised at the noise a fuel pump can make, especially one that's not tightened up good.

 

[not so famous bob]

valve train runs at half the speed of the crank. 1000rpm on the crank is 500rpm at the camshaft.

you might be surprised at the noise a fuel pump can make, especially one that's not tightened up good.

I didn`t read all these posts, but in 1969 I bought a new coronet RT,440 4 speed, w/ power steering only. Car fast as hell on the hi way , not so much in a dragrace. It had a slight knock at idle, turned out to be the heat riser fluttering, I wired it open .