Trouble

[Joe Flanagan]

Well, I was always afraid of this since this is my first ever engine rebuild. Was revving it today, trying to get to the bottom of the stumbling issue and I heard knocking. It's a heavy rapping coming from what sounds like the back of the engine near 5 and 6. It happens when I accelerate rapidly and then let go of the throttle. It's most pronounced at the beginning of the acceleration and then at the end, though I don't know if that's just a trick of sound. It doesn't make this sound at idle, only when I accelerate. I checked the oil pressure and it idles at 40. When I accelerate, the needle climbs to 60, so I believe the pump is working OK. I checked the oil and found I was down a little over 1/2 a quart (various leaks, oil pump repair, etc.). Filled it up and tried the engine again. The sound is still there. It sounds like it's high in the engine, toward the valve side. Again, that may just be a trick of sound but that's my impression of it.

Right now I'm about ready to pack it in for the summer, fellas. I have a lot of house work to do and I could get started on that. But I know this is going to be bugging the heck out of me. I was going to put the hood and fenders on tomorrow, too. The only thing I can think of outside a major mechanical failure is maybe the oil pressure relief valve is sticking? But then my gauge seems to read normally. Oh, and on top of all this, the temperature gauge I bought for 85 dollars is now dead. Reads 110 at all times, whether the engine is running or not.

I'm going to cry in my beer and read the archives. If anyone has any suggestions on what I can try, I'd appreciate it.

[P-12 Tommy]

Boy that sucks!! After all the work. I wish I could be there and check it out and see what it is. Sounds like something like a clip came loose on a wrist pin maybe? I feel for ya man.

Tom

[Joe Flanagan]

I meant to say in my earlier post that I have a very slight amount of smoke coming from my crank case breather tube. It's visible after I shut the engine down. It's not a lot of smoke but it's kind of like vapors. Definitely noticeable but not smoking like a chimney. I don't know if that indicates anything but I thought I'd mention it.

[Joe Flanagan]

Tom, I'm thinking it might be a wrist pin, too. I'm going to go back and look at Blueskies thread on that. If I can fix this by just dropping the pan I'll be happy. But, boy, I didn't want to go through all this. I wonder if it's possible that something is just sticking or maybe oil is not getting to where it's supposed to be? I definitely need to get somebody to listen to this.

[Joe Flanagan]

Thanks. I just thought I read somewhere that that was indicative of something amiss in the engine.

[jd52cranbrook]

You can pull plugs one at a time, and listen.

After that, plastigauge will tell you. Won't take too long and at least you may know what it is.

[Don Coatney]

Probe the noise with a stethscope (SP) to pin point the location. Do this while pulling the plug wires one at a time.

[Brad Lustig]

I'm guessing you've checked the simple stuff like timing, firing order and fuel mixture?

[Joe Flanagan]

I just set the timing this morning. Didn't think to double check the firing order. The engine runs as smooth as can be at idle so I didn't consider that. I don't know that fuel mixture would cause a rapping sound like this. I just had my neighbor over to listen to it and at first he couldn't hear it at all. He thought it was my imagination. Then he finally did hear it.

A really weird thing that I'm sure is not connected is that both my temp gauge and ammeter have stopped working. That's another story, though.

What type of stethoscope is used for this purpose? Also, I'm assuming I have to wear gloves or use insulated pliers to pull the spark plug wires.

[Joe Flanagan]

I do have my timing set at TDC. I was just looking at some old threads and saw that this might be a little on the late side with today's fuels. Could this possibly cause a noise like the one I'm hearing?

[randroid]

Joe,

You can make an acceptable stethoscope from a short piece of broomstick or length of plastic pipe. It should be sensitive enough to pin point any knock you can hear without it.

Don't wear gloves or use any insulation around the plug wires, but be sure to have somebody filming it for later posting on YouTube.

-Randy

[Joe Flanagan]

I just checked out Pete Blueskies thread and he posted a sound clip of what his knock sounded like. It sounds exactly like mine.

[pflaming]

I pulled my wires at the spark plug and laid them on the plugs. I found the wires did not have to be snaped onto the plugs to work. Then I could easily lift each wire to determine 'differences'. It worked for me. Found my problem on the plug #1, the spark was jumping through and into the return heater hose! Rerouted the hose and solved the problem.

A second way is to have a friend help. Have him hold your hand, the jolt will then go through you and into HIM! Only one probem, it takes six(6) friends, probably the ones you will need at your funeral to keep the famly from cremating you. !!!!!!!!!!!

Edited June 26, 2010 by pflaming

[Flatie46]

I do have my timing set at TDC. I was just looking at some old threads and saw that this might be a little on the late side with today's fuels. Could this possibly cause a noise like the one I'm hearing?

Maybe spark knock? Detonation?

[Robert Horne]

Joe, have you done a compression test? I did a compression test on mine, and I have 5 lbs less on number 1, but no noise.

The recent thread on using a vacuum gauge may help also.

[Joe Flanagan]

If I hadn't gotten burned several times this morning while adjusted my timing, I might have fallen for it and tried to pull the plug wires barehanded while the engine was running. As it is I have a healthy appreciation for what's going on in that engine compartment. The terminals on the ignition coil taught me that. Seems I couldn't keep my hands away from them.

Robert, I have not done a compression test. As far as detonation goes, I don't know. This definitely sounds like some kind of impact is happening in there. I guess I could advance my timing and see what happens, but I'm really skeptical that that would make a difference.

By the way, I bought a mechanic's stethoscope. I'll see if I can isolate the sound tomorrow.

[Brad Lustig]

If your mixture is too lean it will cause knocking. It would have to be really lean to knock while not under load. Your valves are all adjusted? I use my longest screwdriver to listen to the engine. Put the tip on the engine and the handle next to your ear.

[Joe Flanagan]

Brad,

I will be trying out the stethoscope this morning. Do you happen to recall which direction of the idle mixture screw is for richer and which is for leaner? I seem to recall counterclockwise to enrich the mixture.

By the way, I'm also going to check the oil pressure relief valve to see if it's stuck. Long shot, I guess, but before I start taking things apart I want to eliminate other suspects.

[Joe Flanagan]

I hate to speak too soon and jinx everything, but it appears the problem was the timing. I had it at TDC to begin with, so I took the advice given here and retarded it considerably. Revved the engine and no noise. I couldn't reproduce it no matter how much I tried. Also, this solved the stumbling issue. The engine runs and accelerates very smoothly. So then I moved the timing back to TDC. The noise was back, as was the stumbling on acceleration. I retarded the timing just to the point where there is no knocking and no stumbling. Vacuum reads about 21 inches at idle. Is it OK for me to keep my timing this late? If this was the solution, it almost seems too good to be true. I've tried on two occasions now to reproduce the knocking sound with my timing retarded and I can't do it.

[Don Coatney]

Joe;

Your engine should run very well with no knocking at TDC. I suspect you did not line up the dots when you installed your timing chain. Or there is a problem with your vacuum or mechanical advance in your distributor not dropping back to ground zero at idle.

[Joe Flanagan]

I'd be surprised if I made a mistake lining up the dots on the gears. I was very careful when I did it and triple checked myself. That doesn't mean I didn't screw it up, but I would be surprised if that's it.

Here's the weird thing. I just now went out to check for the noise, discovered that it was back, and then found out that somehow, my timing had returned to TDC. I thought I must have spaced out so I reset the timing at after TDC, revved the engine and got the knocking sound. Looked at the timing and it was back to TDC again. How could this happen?

When I rebuilt my distributor, I replaced the small wire with a thicker wire than what was there originally. I thought that might have been causing my stumbling problem, so I replaced it with one that matched the diameter of the original. While I was doing this, I noticed that there is a second small wire in the distributor. Back when I rebuilt the distributor, I replaced that one too, with the thicker wire. That is still in there and may be too stiff to allow the distributor to move like it's supposed to.

[Joe Flanagan]

Some pictures from when I assembled my timing chain/gears.

[Merle Coggins]

I think that if the cam timing was off it wouldn't run very good. I have to suspect that your damper marks are off. You may need to pull the plug over #6 and find the exact TDC, then look at the marks on your damper/pulley to see if it points to "0". If it does than Don could be on to something with the advance in your distributor.

Merle

Edited June 27, 2010 by Merle Coggins

[Jim Saraceno]

Here is an article that describes engine knocks. Hope it helps.

The one noise it does not cover is "Ping" or pre-detonation.

Edited June 27, 2010 by Jim Saraceno

[Don Coatney]

I recall a story about Bob Vanbuskirk having his timing gears off by a notch. He was on an extended road trip with Greg G and noticed his fuel consumption was a lot greater than Greg's. His engine ran fine (no knocking etc.) but he could not pass a gas station. He returned home and found his problem upon disassembly.

I think Merle may be on to something with the damper marks not on center and moving. Remove your fan belt and try moving the damper both ways to see if it moves with the crankshaft.