Strange unidentified knock from engine

[iburke]

Well let me ad to your confusion sorry but it sounds like a piston wrist pin to me. Could you make another one with a slow increase in RPM. A wrist pin should have a distinct double knock sound as the rpms increase due to the piston changing direstions at a faster rate.

[AirbornSilva]

Originally Posted by iburke

Well let me ad to your confusion sorry but it sounds like a piston wrist pin to me. Could you make another one with a slow increase in RPM. A wrist pin should have a distinct double knock sound as the rpms increase due to the piston changing direstions at a faster rate.

I'll see if I can get another video tomorrow.

I did adjust the valves today but the only thing I accomplished was to have freshly adjusted valves

[Rip]

Since it's on the passenger side, any chance it's fuel pump related?

[AirbornSilva]

Bought a stethoscope today, was hoping it would be the fuel pump or timing chain but both were pretty quiet...

[AirbornSilva]

well after probing around quite a bit more with the stethoscope I found that it's loudest on #1 exhaust header tube (yeah I know I said it was louder on the right side, guess I'm just a little ). I did try putting some cleaner down the intake and I "think" it may have helped a little but then it might be that I just want something to fix it or tell me what the problem is so I can fix it. I also took a couple more videos as requested but am too tired to go through the upload process now will do that tomorrow. Thanks for the help and suggestions guys!

[iburke]

Get out the wrench's its not going away...

[AirbornSilva]

Originally Posted by iburke

Get out the wrench's its not going away...

Oh come on man, why do you want to harsh my mellow

[AirbornSilva]

I give! I'm going to start looking for another 350 to put in so I can drive the car and do a good build on the numbers matching motor.

Thanks for all the help and suggestions guys

[iburke]

We will see a thread on this swap and rebuild won't we.

Let us know what the knock was when you get it apart...

[AirbornSilva]

Originally Posted by iburke

We will see a thread on this swap and rebuild won't we.

Let us know what the knock was when you get it apart...

Not sure about a swap thread, I'm not good at taking pictures. I will definitely let you guys know what I find, first I need to find a motor on the cheap.

[AirbornSilva]

So I decided to get greasy today, I first put new header gaskets on to see if that would cure the knock, that was a no go but it wasn't a waste of time since the old ones were brittle. I then decided it was time to take the intake of to see what I could see. First look was at the push rods they all look good and straight. I then pulled a lifter at a time and inspected them, they all too looked fine, no evidence of any wear or damage, the bottoms looked in great shape and had no extraneous metal on them that I think (?) would have been there if a lobe was being wiped (or am I way off base?). So I was looking around for something to speak to me when I noticed a puddle of fluid by an intake valve, I thought this was odd and maybe I got coolant down there when I took the intake off so I put a shop towel down there to mop it up, when I smelled it it was fuel not coolant, so I looked in the other runners and found that 3 or 4 more were the same, is this normal? I wouldn't think that much fuel should be there! Could this be my issue, a carb dumping too much fuel?

Thanks for the help guys!

[C5 Dude]

Originally Posted by AirbornSilva

So I decided to get greasy today, I first put new header gaskets on to see if that would cure the knock, that was a no go but it wasn't a waste of time since the old ones were brittle. I then decided it was time to take the intake of to see what I could see. First look was at the push rods they all look good and straight. I then pulled a lifter at a time and inspected them, they all too looked fine, no evidence of any wear or damage, the bottoms looked in great shape and had no extraneous metal on them that I think (?) would have been there if a lobe was being wiped (or am I way off base?). So I was looking around for something to speak to me when I noticed a puddle of fluid by an intake valve, I thought this was odd and maybe I got coolant down there when I took the intake off so I put a shop towel down there to mop it up, when I smelled it it was fuel not coolant, so I looked in the other runners and found that 3 or 4 more were the same, is this normal? I wouldn't think that much fuel should be there! Could this be my issue, a carb dumping too much fuel?

Thanks for the help guys!

You can have a collapsed lifter that is not holding. They buld up with oil pressure and you wont know just by looking at it. Follow below before you put it all back together if you havn't already. A leaky lifter will knock just as your video sounds.

Hydraulic valve-lifters are tested for their leak down rate. A good lifter will leak down slowly but, if it’s plunger is sticking, the leak down rate will be too slow. Its plunger is worn, or the check valve is leaking, then the leak-down rate will be too fast. The tester (figure 3.25) consists of a base with vertical standard carrying a ram. It has a cup with test fluid. The ram is operated by the weight on the end of an arm. A scale and pointer indicate movement of the plunger. A watch is used for timing.
1. Place the lifter in the tester cup and cover with fluid. Either a special light oil or distillate is used.
2. Place the steel ball in the push-rod cup under the end of arm.
3. Work the plunger up and down with the weight until the air is bled from the lifter and it is full of fluid.
4. Adjust the length of arm so that point there is in line with the top mark of the scale when the ram is just touching the ball in the push-rod cup.
5. Raise the lever and let the weight and ram force the plunger down.
6. Measured the time that the pointer takes to move across the scale. This is the leak-down rate.
As an example, a used lifter must take at least 5 seconds, but not more than 60 seconds to leak-down and a new lifter should take at least 10 seconds but not more than 60 seconds. A Doubtful lifter should be tested three or four times. If a lifter does not test within specifications it should be discarded and replaced with a new one.


Call around for a shop that has the tester (be sure to mark them to go back in the same) but I reccomend just replacing them.

[matchframe]

Any updates?

[spikebot 81]

Airborn, This is a little far fetched but something to ponder. I recently had a ticking noise develope on a new engine. Sounded like a exhaust leak or rocker arm adjustment. While I was under the car while running I'm hearing a knock. Very intermittent but sounded like it was coming from the bottom of the engine and loud at times. Well the ticking noise was issue but the knock was more disturbing since this is a new rebuild by a engine shop. I have spent countless hours checking all the suggestions in this thread and a good deal from others as well. What I found was a rocker arm hitting the valve spring retainer. For sure this was the ticking noise I was hearing but also causing a knocking noise transfering through the engine. I replaced the rocker arm, spring retainer and retainer locks and all is quite. I've worked on hotrods for alot of years and never in my wildest dreams would I exspect a valve train issue make such a knocking noise down low.

[grumpyvette]

AirbornSilva where are you located?
If your local to west palm bch fla. I can help?
a logical set of tests should help,isolate the cause quickly, read the linked info below
that sound would make me do a compression test , you may have detonation damage on a piston, if the compression test shows all the cylinders are within about 7%-10% then Id suspect a burnt rocker and then readjust all the valves as the engines idling as a first test.
The sound sounds like a defective rocker , or busted valve spring, to me, you should be able to pull the valve covers one at a time and place your thumb firmly on each rocker applying pressure while the engine idles, if the rockers defective or valve springs busted, youll both hear and feel it binding and the sound will change as you apply some pressure.
once you locate the defective rocker (OR ROCKERS) or busted valve spring,youll want to replace them.


http://forum.grumpysperformance.com/...ng+down#p26074

http://forum.grumpysperformance.com/...ng+down#p19552

http://forum.grumpysperformance.com/...+spring#p26282