Tryng to diagnose a ping in number 6

[sscam69]

Pretty much what the post says.

I am having problems with a ping in the number 6 cylinder of my engine. I really don't know what it could be.

I have set the ignition timing at 16 BDC @idle and I am running @28deg mechanical (with soft springs) and 51@part throttle. The timing seems to be OK.

As some of you know or don't know I just installed a cam shaft but I figured If I installed it wrong then I would be getting pinging from all over the place. I have the stock heads with 78cc chambers and pistons with valve reliefs and then some. I am guess my CR is about ~9:1-~8.x:1. I am running 91 octane in the tank (just filled the other day).

I pulled the spark plugs from the passenger side and the #6 plug was a really light brown, close to white. Then I pulled the #4 cylinder plug and was a medium to dark brown.

I have checked the wires and pulled the wire to the #6 to see if it was firing. It was.

It could be a defective spark plug. BTW their all new plugs.

I am going to swap the spark plugs with another cylinder to see if its the spark plug causing the problem. Oh BTW the spark plugs are Bosch Platinum (single prong, don't believe in that 4 prong:eyerole jaz).

Then I am going to check if I wired the HEI to the right cylinders. I checked it twice before I fired the engine and it was running fine. The problem has seemed to of have developed.

I am going to check all the external equipment first if this does not work out I am going to pull the head and see if there is nothing wrong. The drivers side is just fine.:confused

What do you guys think it could be?

What do you think about my course of action?

any input would be greatly appreciated!

Frank

 

[Mpit69]

How do you know it is positively #6?

 

[cruzer99]

If you hear the "ping"at idle, it's prob not a ping as we think of pings. (pre-detination)

 

[wolf_walker]

Fuel distrobution problem? Running any kind of funny intake or carb? They will sometimes run a cylinder or two a little lean or rich, usually lean on the cylinder furthest away from the carb.

Never heard a ping on one cylinder. How the heck can you tell? A pre-ignition ping should only be under some sort of load, not at idle. ?

 

[mvftw]

First thing I would do is a compression check and if possible a leak-down test. Best way to tell how your internals are

 

[sscam69]

How do you know it is positively #6?

I KNOW its on the passenger side for two reasons.

1. I have a true dual exhaust with no crossover. So each side is isolated. I put my ear to the exhuast and you can hear it on the passenger side. Drivers side sounds healthy

2. When I am standing next to my engine the sound is stronger when I am standing next to the passenger side compared to drivers.

3. The spark plugs (Oops I guess thats a third)

I only checked two spark plugs, I was on the way to school so just out of curiousity I pulled #6 & #4.

Never heard a ping on one cylinder. How the heck can you tell? A pre-ignition ping should only be under some sort of load, not at idle. ?

You can hear it at idle. It sounds like when you shut off an engine but it keeps on going on its own. Wasn't that a detonation problem? Its not just at idle its a WOT. Man does it sound absolutely nasty. The car feels like its lost power big time.

See thats what got me stumped, its only 1 cylinder.:confused If it was a genearl problem I figured it would be all over the place but its not.

I was going to by a stithoscope to try and pin point it better but the plugs gave it away. So it seems I am going lean on #6. I will check the other plugs to check on their condition.

First thing I would do is a compression check and if possible a leak-down test. Best way to tell how your internals are

I'll give it a shot. I really have nothing to lose at this point.

Wow sounds like an odd situation to me:confused

Frank

 

[cruzer99]

As a test, why not back off the timing a couple of degrees to see if there is any differance.

 

[wolf_walker]

You know, I had a intermitent miss/weak cylinder on the 74 for ages before I ever figured out what it was.

Stinking vacume leak. The port for the vacume that was leaking was in the runner going to that cylinder, leaning it out now and again to the point it was missing ocasionally.

Just a thought..

 

[sscam69]

Well guys I figure out the culprit. It was a bad spark plug.

I troubleshot it and nailed it on the head the first time.

Well as mentioned before I narrowed it down to the #6 cylinder.

I had a burnt boot with some metal exposed. I thought that maybe the charge was arcing on the the header for some other metal part so I bought a new wire.

I then proceeded to start the engine and removed the wire at the Dist. to the #6 cylinder. Sure enough there was spark.

So the only two things left were to check under the cap and the spark plug. I went with the spark plug. I removed the plug and told my brother to crank the engine and sure enough there was no arcing across the plug tip.

I went to the parts store and bought a new plug. Bolted it in and fired up the engine. TADA!! no more knock!

I really don't know what could of caused this, other than just a bad plug. So everything is O.K, now to move on to ther issues!