Slant Six Forum :: Another Engine noise thread.

Wrist pin isn't loaded like you think it is. Exhaust stroke the piston is floating unless you have some horrendous pumping losses going on.

There is a misconception that the piston is pushing the exhaust gasses out. It better not be.

A bad wrist pin is pretty rare though. I've had one in a boat load of cars and trucks. Weird noise though.

If the distributor is worn radially, you could have the reluctor contact the pickup in an electronic distributor. If it was a points distributor, it would have died by now. If the distributor was rebuilt used, the axial thrust may be bad. The shaft can move up and down. This can make a noise.
That could be what you are hearing. It could park you on the side of the road at any moment. Could roll 100k miles too.

All we can do is toss WAG's out there.

2Â¢

CJ

Author:	Sam Powell [ Wed Jul 31, 2013 8:34 pm ]
Post subject:	Another Engine noise thread.
This noise has been in the engine for about 2 years. In that time it has not gotten worse. If anything it might be a little less. It may have been there before, and I just did not hear it until my brother pointed it out to me. The noise sounds like a loud lifter. But the valves are adjusted correctly. There is a nice even flutter of solidi lifter sounds. It idles fairly smoothly. It does not seem as if there is a miss in one of the cylinders. It does not sound heavy enough to be a rod or main bearing, nor is it that loud. I got the idea tonight to time the noise. It sounds 24 groups of 4 beats every fifteen seconds. This means it is going at roughly 100 beats every 15 seconds, or 400 beats per minute, at an idle of 800RPM. This would suggest it is in the valve train. I have asked this before, but not with this specific information. Any ideas what could be making this noise in the valve train if the valve is not out of adjustment? Do you think a rocker arm could be shifting sideways and clacking against its neighbor or the spacer tube hard enough to make this noise? This seems to be the month for engine noises. I have followed all the threads discussing similar sounds. Although I listened to the U tube that was linked here, and my noise is nowhere near as loud as that one was. When driving, and pulling under load, I cannot hear it at all. I am taking it on a fairly long trip this week end, and I was a little concerned about the noise maybe being a sign of real trouble. However, timing the noise and concluding that it is valve train related gives me more confidence that the engine is not going to fly apart on the highway. I am hoping someone will say,"Yeah go ahead and drive it. Nothing bad will happen. Noisy valve trains never make an engine break down." Sam

Author:	jhdeval [ Wed Jul 31, 2013 8:59 pm ]
Post subject:
I am going to throw a guess in on this one. Since it appears to run at half the RPM I would think it maybe either intake or exhaust related but not both. You indicate that the valves are adjusted correctly are you sure they are not slightly to loose? I do not think it is mechanical failure because it would be consistent but I would not think it would equate to exactly half the rpm. Half you checked the exhaust donut? Can you pinpoint specifically where the nose is? One way would be to use a long screwdriver and place your ear on it. It then works like a stethoscope.

Author:	ceej [ Wed Jul 31, 2013 9:57 pm ]
Post subject:
Maybe if you hum a few bars... Other possibilities: Worn rocker shaft. Wrist pin - some of the noises I've dealt with were pretty odd. Fuel pump noise. (Not half time, but it can present strangely.) Worn distributor, check for a bent distributor shaft. Bent pushrod worn rocker at valve stem. A mechanics stethoscope might come in handy. A hand held flat against a screwdriver, with your ear on the other side works. 2Â¢ CJ

Author:	emsvitil [ Wed Jul 31, 2013 11:37 pm ]
Post subject:
Rocker arm adjuster hitting the valve cover (as per another post) Actually the fuel pump would be half time as it's driven off a seperate lobe on the camshaft.

Author:	SlantSteve [ Wed Jul 31, 2013 11:54 pm ]
Post subject:
Does the noise change with load?

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Another Engine noise thread. https://slantsix.org/forum/viewtopic.php?t=52911	Page 1 of 3

Author:	wjajr [ Thu Aug 01, 2013 4:58 am ]
Post subject:
This is my method: Get a length of tubing that will slide into your ear, remove valve cover, and point free end of tube to all points of contact in valve train. You will be able to discern where the odd sound is coming from.

Author:	Sam Powell [ Thu Aug 01, 2013 6:00 am ]
Post subject:
Wow! All good ideas. Where to start? 1. Fuel pump is in tank. 2. Wrist pin noise would be 800 rpm at idle. 3. Noise is there with valve cover off. 4. I do not remember this noise being there before this distributor was installed. In fact when my brother and I went down to Va Beach almost 2 years ago today, it was after we put this distributor in that my brother heard the noise. I did not relate it to the different distributor being installed, and simply assumed the noise had been there and I had not heard it before. So what makes the noise in a distributor? Is it doing damage? If it runs OK, is it alright to simply let it be there, or is there urgent need to pull it and replace it? I have put about 2500 miles on it with this noise. Sam

Author:	ceej [ Thu Aug 01, 2013 6:50 am ]
Post subject:
Wrist pin isn't loaded like you think it is. Exhaust stroke the piston is floating unless you have some horrendous pumping losses going on. There is a misconception that the piston is pushing the exhaust gasses out. It better not be. A bad wrist pin is pretty rare though. I've had one in a boat load of cars and trucks. Weird noise though. If the distributor is worn radially, you could have the reluctor contact the pickup in an electronic distributor. If it was a points distributor, it would have died by now. If the distributor was rebuilt used, the axial thrust may be bad. The shaft can move up and down. This can make a noise. That could be what you are hearing. It could park you on the side of the road at any moment. Could roll 100k miles too. All we can do is toss WAG's out there. 2Â¢ CJ

Author:	Sam Powell [ Thu Aug 01, 2013 7:15 am ]
Post subject:
Quote: Wrist pin isn't loaded like you think it is. Exhaust stroke the piston is floating unless you have some horrendous pumping losses going on. There is a misconception that the piston is pushing the exhaust gasses out. It better not be. A bad wrist pin is pretty rare though. I've had one in a boat load of cars and trucks. Weird noise though. If the distributor is worn radially, you could have the reluctor contact the pickup in an electronic distributor. If it was a points distributor, it would have died by now. If the distributor was rebuilt used, the axial thrust may be bad. The shaft can move up and down. This can make a noise. That could be what you are hearing. It could park you on the side of the road at any moment. Could roll 100k miles too. All we can do is toss WAG's out there. 2Â¢ CJ Could you go a little deeper with the exhaust gas expulsion thing? How does it get out if not pushed out? What does WAG's mean? Sacm

Author:	Rug_Trucker [ Thu Aug 01, 2013 7:29 am ]
Post subject:
Cut open your filter

Author:	Sam Powell [ Thu Aug 01, 2013 11:45 am ]
Post subject:
Looking for metal?

Author:	87D100 [ Thu Aug 01, 2013 4:30 pm ]
Post subject:
WAG= Wild A$$ Guess

Author:	wjajr [ Thu Aug 01, 2013 5:37 pm ]
Post subject:
Quote: WAG= Wild A$$ Guess SWAG = Scientific Wild A$$ Guess

Author:	ceej [ Thu Aug 01, 2013 6:03 pm ]
Post subject:
Scavenging is how the gas gets out. That's why too large an exhaust can cause power to drop. Exhaust gasses are very hot, and under a lot of pressure. The exhaust valve opens before the piston has to push it out, keeping the exhaust gasses hot, and moving through a tuned length head pipe creates a large mass of moving fluid. (Exhuast gasses) The velocity of the mass is kept high because it hasn't cooled off a whole bunch. This causes the piston to, in effect, follow the gasses up the bore. As the volume decreases, we still have a high velocity charge traveling down the head pipe. Before the exhaust valve closes, the intake valve starts opening. The exhaust gasses flowing mass starts pulling a vacuum in the remaining chamber, helping intake charge to be pushed into the cylinder by atmospheric pressure. The mass in the intake runner builds velocity, the exhaust valve closes, and follows the piston down the bore. The piston should not be doing any work during the exhaust or intake cycle. It's just along for the ride. Once the intake closes sometime after bottom dead center, the piston starts to do work. This is of course when the engine is operating within it's efficiency range. There are pumping losses at partial throttle settings, and at engine speeds outside the range of the cam and engine configuration. When we fire the charge, maximum expansion is realized 15-20Â° ATDC. This is when the power can be extracted. Clear as mud? CJ

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Author:	Sprag [ Thu Aug 01, 2013 6:13 pm ]
Post subject:
EDIT: CJ, I was typing below as you entered your last post - I like, but my brain still hurts.. Quote: There is a misconception that the piston is pushing the exhaust gasses out. It better not be. CJ Quote: Could you go a little deeper with the exhaust gas expulsion thing? How does it get out if not pushed out?..... I thought it was pressure differential, the same things that pushes the mix into the engine thus nixing the opposite theory that the piston 'sucks' the mix in. At least that's what I thought in order to visualize how a carb works, I visual atmospheric pressure as an external force that 'rams' the mix into/through the engine (14.7 psi +/- right?). Then, if I'm nearly correct, at the exhaust where the atmosphere is on the low side, it 'yanks' the mix back out. Or maybe I need another beer.