kalli

hi all, as said I'm deaf to knock, but probably just for the reason I can't identify it.

found a video on youtube where there's a definite knocking sound that is not related to pistons/rods/tappets ... whatsoever.
it's some background noise when he accellerates but disappears as soon as he lets off

Is this engine knocking caused from advanced ignition/too lean etc ???
if yes, then finally i know what to look out for. I know that sound from another car

http://www.youtube.com/watch?v=TPYxoFwG5io

Kalli

JMD

By what I can hear I am guessing an exhaust leak....

kalli

i'm still trying to find what exactly it sounds like. when driving in 5th at 30mph and just starting to accellerate there's the faintest sound of the only thing ever I heard and kinda matches the desciptions marbles in a tin pot. maybe that's it. i'll keep hearing ...

JMD

"Marbles in a tin pot" on a 302 sounds like a scant touch of detonation...

Many years ago I had a 90 Mustang 5.0, on hard accereration in higher gears it WOULD ping.... like marbles in a tin pot...

The 90 was computer controlled so it never was much concern to me. Maybe try a higher octane gas or octane improving additive as a test...

I was under the impression that the gas in Europe was generally of a better octane grade than we have here.... even with marginal gas at my elevation 10 to 1 compression is not usually a problem...

kalli

yah. have 10:1 and what we get is usually 92 octane. my petrol station (next door) has 95. i try to use only that. but I don't have any issues that I would relate to low octane like running on (dieseling on). no sutch thing.
I've ordered a set of autolite spark plugs (the ones 67m302 suggested) to get a reading if I actually ping or not.

Kalli

fakesnakes

What you are hearing when he revs the engine under no load is engine knock or detonation (all that other sewing machine noise is normal four cylinder valve train chatter). That engine has a knock sensor that will retard the timing when it detects knock. It can not respond fast enough when he revs it under no load. On most of our engines, the only remedy is higher octane fuel, retarding base timing, slowing the rate or peak of mechanical advance, or adjusting, adding, or eliminating vacuum advance.

KMatch

90% chance it's spark knock/detonation, 10% chance it's worn piston skirts slapping the cylinders with a sudden load change. Many years ago I had a Chebby 350 at the dealer I worked at and you could actually see the parting line on the crankshaft where the lower end of 2 connecting rods were slapping each other which was a very similar noise. That doesn't apply to a 4 or inline 6 banger, and ain't likely ever to be seen again in the history of mankind, but just sayin'...

kalli

thanks lads.... there's a lot of chatter at the engine (injectors etc). but yes. that specific knocking just as he accellerates. if that's the engine knock everyone is on about I finally know what it sounds like as I can hear that and heared it before.
and yes it sounds like a piston slapping. like if then conrod bolts were loose or something

Kalli

KMatch

Another little tidbit about detonation and why it's deadly to anyone not knowing the true details. When a fuel/air mix fires, it's not an explosion as old wives tales would say. This is why timing is critical as the mixture expands just in the nick of time to shove the piston down. It's like riding a bike. You don't hammer the pedals, you push as they roll past the top. Detonation, on the other hand, isn't a shove. It's actually closer to the actual explosion and caused by an out of control fuel/air mix going off too soon or uncontrollably due to pisspoor gas. That little knock we hear is like a hammer whacking the top of the piston - except everything inside the cylinder "feels it". A small hammer with hundreds of little taps causes no harm. A larger hammer with a considerable whack will kill the weakest link. Head gaskets get pushed out of place, pistons get cracked, upper rod bearings get deformed. How much is too much? The little hammer that causes no or little damage, you won't even hear from the seat. If you're hearing it while driving, damage will happen if not controlled.

scootchu

That's the sound I get when I just get on the throttle, usually in third or four gear when my timing isn't dialed in and I thought it was detonation or pinging. It seems to happen just at that point and more throttle and it goes away.
I know that you and I seem to have similar situations with our 302's.