I have a 69 f100 with a 360 and a three on the tree. sometimes when the truck is put under a position where alot of torque is needed it starts to knock and sound like a diesel. One example is when I go around a corner and downshift into second and then I stomp the gas which is putting alot of strain on the engine.(I don't do this alot) The engines rpms eventually catch up to the amount of gas I am feeding it and the knocking will stop. My guess is that it is the piston slapping around in its bore. I would think that the gas is going into the cylendar and the spark plug is firing it but since the truck is requiring so much torque to move that the piston can't go down as fast as I want it to and the force put on the piston by the firing of the fuel is causing it to rock on its wrist and hit the sides of the cylendar. Am I right? If this is true technically isn't this what is happening in new or rebuilt engines when they are put under the same amount of torque, but you just can't hear the knocking because the cylendars haven't worn enough to alow for the piston to rock in it's bore? It does not knock when I simply rev the engine or press the gas normaly or even when I press fast and steadily for a speady pick up. Am I correct about all of this?
thanks for any info
brad

 

THAT IS CALLED DETONATION OR PING!!!!!!!! Don't let that happen if you can help it. It will, with time, blow a hole through the top of your pistons. That is what happens when your hear that knock. With a stock cast piston you aren't looking at a lot of life if that happens much.

The cause could be improper timing, not enough ocatne in your gas and to much compresion. If you are using the cheapo 86-87 octane gas bump that up to a 91-92 and see if that helps. if it happens after that then you are in need of some changes.

Someone else will chime in and give other ideas as to what could be causing the PING. But for now try the higher octane and we can go from there.


Scotty

 

Hey Brad-

If that's the only time you hear it, it's normal. You can make a brand new truck with a manual transmission do the same thing. I don't know how long you've been driving a three on the tree but it does take a little bit more grace than a floor shift. Just don't accelerate so hard after completing your turn.

Now, if it happens under normal driving conditions while accelerating, that is when it becomes a problem.

Joe

 

There are several noises you might be dealing with under power, and all can become very serious very quickly if not dealt with soon. The more immediately serious one is knocking, and it occurs in the bottom end. Usually it is a rod bearing gone bad. Keep going with it, and your engine will have itself for luch, and turn, not into a pumpkin, but into a very expensive boat anchor.
This usually sounds like a hammer banging on a heavy piece of metal (not sheet metal).
The other major engine sound is pinging, and sounds like marbles rolling around in a can, or like a diesel as you mentioned. It has a number of potential causes, one of which was mentioned, low octane gas for the compression you're running.
Other causes are:
Too lean mixture, caused by improper carb settings, too small carb jets, or an air leak, usually in a broken/cracked rubber hose, the intake manifold joints or carb spacer.
Timing too advanced.
Engine too hot.
Valves improperly adjusted (doesn't apply to hydraulics)
Hope this helps!