Noise in 340...help

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cmills

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Something strange happened today when I went to start my car....just to hear it run. First of all it wouldn't start..that was my bad because I knocked a wire loose when cleaning under the hood. Once I located and re-connected the wire I turned the key and immediately it started BUT I heard a noise at the same time that it "fired". It wasn't loud but obviously different. Now while it runs I hear a "knock". The noise does not go away. WHY!!! What should I look for? It still runs smooth but the knock is evident. Any advice? FYI...it is cold here. Well only about 30 degrees.
 
Knocks are not good. If you hold a long screw driver, or extension down on the motor, then touching right up behind your ear, pressed to you,, you can usually tell how deep the sound is. If you move it around on the motor, you can tell where it is coming from. If you hear/feel a nice smooth "whur", that is good, it is a bearing whur.

If it is really a knock, and not clatter, you need to take it apart.

I usually drain the oil, look for metal flake, the bigger the flake, the worse it is.

But each time it is knocking, it is doing more damage.
 
As suggested, listen to the engine to id the location of the knock, that may give you an idea where it is coming from. Then use a solid rod or mechanics stethoscope around the engine to listen to the knock.

Does the knock go away while increasing RPM or does it get louder?
 
How long has it been sitting? After a couple of weeks the oil will drain out of the lifters and they will clatter until they fill up with oil. Sounds like you have one that isn't filling up. Looks like it's time to clean out the varnish and see what else needs to be done.
 
Actually you may have something there. It sat for two weeks in a cold garage so maybe.......I didn't leave it run very long when I heard the noise. I got bummed out and parked it. So tomorrow I will let it run longer see what happens. Does anyone agree that is a good idea?
 
AND if I remember correctly the noise did seem (wishful thinking) to lessen slightly as it ran-------(about 2 minutes)
 
cmills said:
AND if I remember correctly the noise did seem (wishful thinking) to lessen slightly as it ran-------(about 2 minutes)
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There is a definate difference between a knock and clatter. A lifter will clatter, I hope for your sake it is a clatter.
 
We Almost Had To Call It A Lemon ,and Gang Up On The Seller.
Glad Too Hear It Quieted Down..
 
hemied said:
There is a definate difference between a knock and clatter. A lifter will clatter, I hope for your sake it is a clatter.
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That's normally the case but I had one with 2 bad lifters that wouldn't pump up and they sounded so bad you'd think it was knocking.
 
Drag 340 might have something. The wire that I found that I knocked off "seemed" to go from the electronic ignition module to the ballast resistor. I looked online before I attached it there and from my reading it appeared obvious that's where it went....since immediately upon attaching there the car started. Drag340 is suggesting that I may have attached it at the wrong terminal causing an ignition problem/noise. As a matter of fact the noise the car made upon start-up reminded me of another 340 I had that had a timing issue at one time. But that car didn't knock AFTER start-up. The wire in question is light blue with a yellow stripe. I attached it to the left terminal on the ballast resistor. The other terminal had two wires connected to it running from the voltage regulator. Again.....your suggestions are welcomed.
 
Please be more specific on the type of noise. Here are some suggested adjectives.

Loud rapping sound
Sharp double knock
Dull rythmic thumping
higher pitched tinny tapping noise

It would also help to know how the car is equipped, headers, 4 speed or auto, does the noise change when you push on the clutch or put it in gear? Can you pull a plug wire and make it stop? Does it get louder and/or faster, with RPM etc.?

Many times diagnosis is just a simple process of elimination. By isolating the things it is not you can deduce what it is.
 
cmills said:
Drag 340 might have something. The wire that I found that I knocked off "seemed" to go from the electronic ignition module to the ballast resistor. I looked online before I attached it there and from my reading it appeared obvious that's where it went....since immediately upon attaching there the car started. Drag340 is suggesting that I may have attached it at the wrong terminal causing an ignition problem/noise. As a matter of fact the noise the car made upon start-up reminded me of another 340 I had that had a timing issue at one time. But that car didn't knock AFTER start-up. The wire in question is light blue with a yellow stripe. I attached it to the left terminal on the ballast resistor. The other terminal had two wires connected to it running from the voltage regulator. Again.....your suggestions are welcomed.
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The wire you described sounds like the power wire to the ballast resistor. It won't run without it and I can't figure out how you could have connected it wrong anyway as there is nothing else close by it may have gone on, Is there? Your best bet is to describe the sound better like GuitarJones said. Then maybe we can help more.
 
fishy68 said:
That's normally the case but I had one with 2 bad lifters that wouldn't pump up and they sounded so bad you'd think it was knocking.
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My first experience with "throwing a rod" was my 57 Fury in 1966, in fact Ted Detar (http://kansasbadman.com/_wsn/page4.html) told me exactly which two rods. He put a long 3/8 extension down on the motor, moved it around a few places, and said: #7 and #8 are spun, then walked off.

When I pulled it apart, he was right, both 7 and 8 were spun to my amazement.

I have thrown many, many rods since, and they have always sounded that same sickening way.

But a lifter, as you say, usually just ticks, but they can get loud.
 
limelite70 said:
We Almost Had To Call It A Lemon ,and Gang Up On The Seller.
Glad Too Hear It Quieted Down..
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Please be careful what you post about a person you know nothing about Jerk!!!

Any flaws the car has were discussed openly and honestly between the seller and the buyer and NEITHER of which were YOU so please keep your comments to yourself.
I have been in constant contact with him and have nothing to hide or did nothing wrong!

This is EXACTLY what I hate about the internet, people chiming in with no knowledge on the subject just putting in their opinions.
He posted looking for help and possible solutions, neither of which you offered.

Sorry for the rant but I don't enjoy having a lynch mob called out on me!
 
I was gonna say be careful on that one because shizzle does happen and I feel bad for guys who sell cars that have never had a problem and then things start to go wrong with e motor or drivetrain and the buyer thinks he got a lemon, but anyone with half sense knows that things can just go wrong with no warning, that's just life.
 
I Was Kidding Ratman.
Your Write I Should Have Kept It To Myself.
 
do you have an electric fuel pump? i hope it didnt flood while the wire was off and bend a rod when cranked as liquid doesnh compress.
 
limelite70 said:
I Was Kidding Ratman.
Your Write I Should Have Kept It To Myself.
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No problem, as long as it was said in jest. Unfortunately what we think in our head doesn't always come across in our written word.

Lets all work together and try to help him out, that's the reason this site is as good as it is. There are a lot of helpful people here with a wealth of experience and knowledge. Let's get this resolved for him.

P.S. Sorry about the 'Jerk" comment!
 
If I may chime in. As the buyer I fully understand the seller is NOT at fault. He feels sick about this and is offering his expertise to arrive at a conclusion to this problem. I gotta say....this car is still B.A!
 
Dumb question here.

To adjust the rockers are the a torque to spec or do they adjust like a (dare I say it) Chevy lifter (tighten to quiet and add a 1/4 turn)? They are hydraulic lifters.
 
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