Upper end knock

[BreckAConner]

Okay, if it was combustion detonation would it stop if pulling the plug on that cylinder? What I did was pulled each plug individually for each cylinder to see if the knock would stop, and it didn't at that rev range for each cylinder. So yet I'm still to figure out if it's internal or what. I have my fingers crossed it's not any rods knocking. Last thing I want to do is rebuild my motor.

[johnl]

Okay, if it was combustion detonation would it stop if pulling the plug on that cylinder? What I did was pulled each plug individually for each cylinder to see if the knock would stop, and it didn't at that rev range for each cylinder. So yet I'm still to figure out if it's internal or what. I have my fingers crossed it's not any rods knocking. Last thing I want to do is rebuild my motor.

You could well have detonation in all cylinders...

Detonation sounds like a metallic rattling.

[BreckAConner]

You could well have detonation in all cylinders...

Detonation sounds like a metallic rattling.

What can I do to fix this, It would be a timing issue right?

[Raf99]

What can I do to fix this, It would be a timing issue right?

Detonation can occur from timing issues, fuel issues, hotspots, O2, temperature, spark plug issues, knock sensors, etc.

You should pull the plugs ASAP and take a look at them. Any detonation will show on the plugs. I would also recommend using a scope to look in the cylinder to check for damage (thinking the piston is hitting a valve), and if you can get a stethoscope try to listen for where exactly the noise is coming from in the engine.

If you can take your car to a shop who has the tools to tell you what's going on before your engine take a turn for the worst.

If you can post pictures of what you find in here we can try to help too.

[BreckAConner]

Detonation can occur from timing issues, fuel issues, hotspots, O2, temperature, spark plug issues, knock sensors, etc.

You should pull the plugs ASAP and take a look at them. Any detonation will show on the plugs. I would also recommend using a scope to look in the cylinder to check for damage (thinking the piston is hitting a valve), and if you can get a stethoscope try to listen for where exactly the noise is coming from in the engine.

If you can take your car to a shop who has the tools to tell you what's going on before your engine take a turn for the worst.

If you can post pictures of what you find in here we can try to help too.

The plugs would be black or scorched right? I pulled the plugs the other day to do a valve adjustment so it was easier moving the crank, the plugs looked like normal wear, they weren't charred or scorched.

[johnl]

What can I do to fix this, It would be a timing issue right?

I don't know if you have detonation or not. I haven't viewed your video because my computer is currently without sound, so there's no point.

[wildBill83]

I hear valve lash and something that sounds like maybe there is a valve seat problem. It's hard to tell. When you did the oil pump was it from a failure of some sort? Could anything have damaged the cam? Oil starvation? Lose metal?

I doubt it is a timing problem.

[Raf99]

The sound in the video you are trying to point out, is it the one that sounds repetitive, like the clunking an old engine gets when its about to stall out?

Like it sounds like you're revving it or is that the sound?

[johnl]

The plugs would be black or scorched right? I pulled the plugs the other day to do a valve adjustment so it was easier moving the crank, the plugs looked like normal wear, they weren't charred or scorched.

Black would indicate an overly rich air / fuel ratio, not detonation. Detonation can leave a spotty appearance on the plugs, or the plugs may be physically damaged if detonation is severe.

Detonation is caused by some part of the air / fuel charge spontaneously igniting as a result of a localised high temperature region in the air / fuel in the combustion chamber. As a result there are two flame fronts within the cylinder, one caused by the spark and the other caused by the detonation. This is most likely to occur after the spark has ignited the first flame front, which instantly radiates heat throughout the combustion chamber and raises the in cylinder temperature.

When the two flame fronts 'collide' there is an instantaneous pressure spike within the cylinder that causes a shock wave that is the noise you hear. The pressure spike can damage pistons, valves , spark plugs. Light detonation rarely does much damage, unless quite severe and / or allowed to continue for a long time, but this doesn't mean that it shouldn't be considered a potentially serious problem.

The high temperature that causes the spontaneous combustion 'event' can be as a result of high combustion temperature caused by a lean AFR, or general engine overheating. A lower than required fuel octane will self ignite at a lower than anticipated temperature. It's never (or rarely?) caused by a glowing hot-spot in the cylinder (e.g. a bit of glowing carbon), which is much more likely to cause 'pre-ignition' much earlier than the spark plug ignites the air/ fuel, and is usually far more catastrophic (and non-audible).

Overly advanced ignition timing (either set too advanced or too advanced for the momentary in-cylinder conditions, if something is wrong) gives a longer time for heat radiated from the spark generated flame front to cause a temperature rise in the as yet un-ignited fuel elsewhere in the cylinder, causing a detonation. Retarding the spark timing can prevent this from occurring. If the ignition timing is correct (i.e. 'normal') but a detonation is occurring then something else is causing the detonation. A knock sensor (not that the CB7 engines have one...) will tell the ECU to retard the timing until detonation is no longer being detected, but it's really a band-aid on the problem.

If all is well then no detonation should occur, and the knock sensor shouldn't come into play. A knock sensor may well prevent damage, but it's not a solution to the problem that is causing detonation in the first place. An engine running retarded timing as a result of detected detonation will have less power and worse fuel economy.

[johnl]

The sound in the video you are trying to point out, is it the one that sounds repetitive, like the clunking an old engine gets when its about to stall out?

Then that is likely to be piston slap, i.e. worn piston skirts.

[BreckAConner]

Then that is likely to be piston slap, i.e. worn piston skirts.

If it is piston slap, should I be worried? Wouldn't it smoke if that was the case, and how can I check this problem?

I hear valve lash and something that sounds like maybe there is a valve seat problem. It's hard to tell. When you did the oil pump was it from a failure of some sort? Could anything have damaged the cam? Oil starvation? Lose metal?

I doubt it is a timing problem.

Old oil pump was junk, bought a new one. New one had cheap studs for the vacuum pick up tube and they broke. I noticed I wasn't getting oil to the top of the motor and I was driving the car with very little oil pressure and didn't know it until I pulled the pan one day to see what was going on and why my car was running like crap. That's when I found 1 stud in the pan, the other one in the pick up tube.

As for the Cam, it looks good no scratchs or streaks. I have another motor over at a buddies house, I bought the car from a auction with a bad HG. Now that cam looked horrible and the car still drove fine. So I know the cam and crank looks good. I keep checking my oil every day and I haven't seen any metal shavings, and the oil doesn't look silverish. This weekend I'm going to pull the filter and cut it open to check, I can't remeber who suggested that.

The sound in the video you are trying to point out, is it the one that sounds repetitive, like the clunking an old engine gets when its about to stall out?

Like it sounds like you're revving it or is that the sound?

Yeah I was revving it. The problem will sound at its worst when I have a load in the rpm range. After that certain range the noise goes away. The motor only has 134,000 on it.

[wildBill83]

A low mileage motor can be just as worn as a high mileage motor.

[johnl]

If it is piston slap, should I be worried? Wouldn't it smoke if that was the case, and how can I check this problem?

Yeah I was revving it. The problem will sound at its worst when I have a load in the rpm range. After that certain range the noise goes away. The motor only has 134,000 on it.

Without actually hearing the noise, the symptoms would fit with piston slap (but doesn't guarantee this is your problem). Piston slap tends to occur when the cylinder pressures are highest (under load at / around the peak torque output), and causes the pistons to rock forcefully around the piston pin axis and for the skirts to impact the bore walls, more so the greater the skirt to bore clearance.

It's not a good thing, but some engines can 'piston slap' even when the clearances aren't all that bad (it will be affected by geometries such as skirt length, piston pin height relative to the skirt and crown, pin offset in the piston, con rod angularity).

My engine will occasionally do it if I'm careless enough to lug it at very low rpm, but from your description it sounds like your problem is much worse than mine (if indeed this is your engines' problem). If this is the problem then there's not much that can be done short of replacing the pistons. The engine may slap away for a long time before a piston fails, or it may die tomorrow. Excessive lateral piston movement / rocking may or may not cause significant ring leakage, or be associated with it, but it won't be helping.

It might be possible to check the skirt clearance by dropping the sump and reaching up with a feeler gauge to measure the clearance, but I don't know how easy / possible this might be, never tried to do it. If you try to do this be aware that the clearance is likely to be less at the bottom of the piston stroke than near the top, taking potential bore wear into account.

[BreckAConner]

Without actually hearing the noise, the symptoms would fit with piston slap (but doesn't guarantee this is your problem). Piston slap tends to occur when the cylinder pressures are highest (under load at / around the peak torque output), and causes the pistons to rock forcefully around the piston pin axis and for the skirts to impact the bore walls, more so the greater the skirt to bore clearance.

It's not a good thing, but some engines can 'piston slap' even when the clearances aren't all that bad (it will be affected by geometries such as skirt length, piston pin height relative to the skirt and crown, pin offset in the piston, con rod angularity).

My engine will occasionally do it if I'm careless enough to lug it at very low rpm, but from your description it sounds like your problem is much worse than mine (if indeed this is your engines' problem). If this is the problem then there's not much that can be done short of replacing the pistons. The engine may slap away for a long time before a piston fails, or it may die tomorrow. Excessive lateral piston movement / rocking may or may not cause significant ring leakage, or be associated with it, but it won't be helping.

It might be possible to check the skirt clearance by dropping the sump and reaching up with a feeler gauge to measure the clearance, but I don't know how easy / possible this might be, never tried to do it. If you try to do this be aware that the clearance is likely to be less at the bottom of the piston stroke than near the top, taking potential bore wear into account.

I'm leaning towards it being piston slap. Wouldn't that cause metal shavings?

[wagon-r]

I'm leaning towards it being piston slap. Wouldn't that cause metal shavings?

Probably not. Both the piston skirt and the cylinder wall are very smooth and very strong. It just accelerates wear.