Solid Snake

I may have been running timing advance beyond the recommended maximum for a short time (acceleration was suffering). Soon after I perceived the knocking I backed off and brought her home. Now I have the timing set right, but I'm trying to figure out if it damaged anything. I hear a rattle between 4-6K that increases with load, not really sure if it was there before. I can't tell if this is the engine rattling or maybe a loose washer in the dash or something. No reason it should be detonation as I've properly set the timing with a light and the motor is getting plenty of fuel. The engine seems solid, but are there any non-catastrophic symtoms of knock that I should look for?

Lizard928

if you had destroyed it, it would have happened already.

These engines are very tough.

jpitman2

You might have eroded some of the piston crowns if you had run long periods pinging, especially if there are any sharp edges on the top. If the plug electrodes look ok I doubt there will be any ill effects.
jp 83 Euro S AT 51k

AO

Pull the spark plugs and examine them. If you do a search online you should be able to find examples of spark plugs exposed to detonation and compare yours to that.

I was detonating for a full year and I could not find any evidence of physical damage from pinging aside from some slight pitting on the spark plugs, but then my car has knock sensors and will retard the timing up to 9* to counter the knock. You don't say what year your car is, but if you're manually setting your timing, then you probably do not have knock sensors.

SwayBar

A simple check is to do a compression test on each cylinder to determine whether you've cracked any rings (..which I doubt). If compression is okay, I wouldn't worry about anything else; you're good-to-go.

Jim bailey - 928 International

You pretty much just need to run it. If it gets worse then you may have an issue.

Solid Snake

I was running a few seconds at high RPM and medium to high load. When the vacuum retard let off, the detonation was worse and consistant until I let off the gas and limped home. BTW, I have a 79. I'll see if I can get the tools to do a compression test. I suppose I'll never know if I hurt the bearings since I can't discern any change in the way the motor feels or sounds. I will check out the plugs though.

AO

If it was only for a few seconds... you're worrying WAY too much in my opinion. Detonation, is more like chinese water torture to your car. A drop hear and a drop there doesn't hurt, but if it continues for a prolonged period of time (months or years) then it begins to take a toll.

Joe F

I wouldn't want to worry you unnecessarily, but the above does not match my experience. I had a race car motor that had a detonation problem from a mixture that was too lean. It took exactly two laps, or about 3 minutes to rattle cracks in the ring lands on two of the four pistons. Brand new Jahns forged pistons were immediately turned into paper weights. Detonation is ugly and can harm your motor a lot! And, if severe enough it does not takes years, months, weeks or even days. Only a matter of minutes.
Good luck.

928SS

mark A just lost a motor to detonation too when it overheated and started detonating.. I saw the headgaskets and they looked like someone had been hitting the firerings w/an axe, was amazing.

Charley B

Is that what happened at Laguna?

toofast928

Na nothing happened. I rattle the pistons few times. Off boost.

On boost cracked three pistons.

Tony

928SS

think that happened at road america/someplace east and really hot... iirc, mr fan's had a recent setback related to bad harness wiring/ignition trigger short that caused some misfire damage. w/a little TLC and some $$ I suspect both will be terrorizing the tracks in full form w/a vengance soon.

but it didn't take long for either to have some internal damage.

dr bob

The banging that's load-sensitive sounds too much like a damaged bearing to ignore. Dropping the pan is no fun, but is better that finding later that yiou damaged a bearing -and- trashed the crank br continuing to drive it.

Drop the pan, and inspect/measure the rod bearings.


My too sense...

Solid Snake

That high rpm rattling is POSSIBLY coming from the engine, but it could be something in the dash as well. It's clearly audible from inside the car, but not from under the hood. Spark plug electrodes are clean, they're not gummed up or coked up, but that last thread that's exposed to the chamber is blackened. It's expected as I'm erring on the rich side until my wideband arrives. The plugs have been in for about 300 miles.